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Content

CONTENTS
1. INTRODUCTION
2. INDICATIONS FOR OCCLUSAL REHABILITATION
3. GOALS OF FULL MOUTH REHABILITATION
4. ANATOMY AND PHYSIOLOGY OF MASTICATORY MECHANISM
5. THE HINGE AXIS
6. CENTRIC RELATION
7. VERTICAL DIMENSION
8. FUNCTIONAL ASPECTS OF COMPLETE MOUTH REHABILITATION
9. DIAGNOSIS AND TREATMENT PLANNING
10. PREPARATION OF THE MOUTH FOR REHABILITATION ll.PMS
PHILOSOPHY
12. SELECTING INSTRUMENTS FOR OCCLUSAL REHABILITTION
13. MOUNTING MODELS
14. FUNCTION AND IMPORTANCE OF ANTERIOR GUIDANCE
15. PRINCIPLES OF OBTAINING OCCLUSSION IN OCCLUSAL
REHABILITATION
16. RATIONALE AND TECHNIQUE OF BIO MECHANICAL OCCLUSAL
REHABILITATION
1.7. RESTORING LOWER ANTERIOR TEETH

1

18. RESTORING UPPER ANTERIOR TEETH
19. THH PLANE OF OCCLUSION
20. POSTERIOR OCCLUSAL MORPHOLOGY 2!. RESTORING LOWER
POSTERIOR TEETH
22.WAXING TECHNIQUE FOR LOWER POSTERIOR TEETH
23. RESTORING UPPER POSTERIOR TEETH
24. FUNCTIONALLY GENERATED PATH
25. PROCEDURAL STEPS IN RESTORING OCCLUSION
26. REVIEW OF LITERATURE
27. SUMMARY

2

INTRODUCTION
Planning and executing the restorative rehabilitation of a decimated occlusion
is probably one of the most intellectually and technically demanding tasks
facing a restorative dentist.
The term "occlusal rehabilitation has been defined as the restoration of the
functional integrity of the dental arches by the use of inlays, crowns, bridges
and partial dentures". Occlusal rehabilitation therefore involves restoring the
dentate or a partially dentate mouth. The aim is to provide an orderly pattern of
occlusal contact and articulation that will optimize oral function, occlusal
stability and esthetics.
Occlusal adjustment by grinding may be required, as part of the rehabilitation
but does not constitute rehabilitation per se.
Occlusal rehabilitation is discussed in the context of cases where restorations
are supported by natural teeth and doesn't include the restoration of the fully
edentulous arch or maxillofacial defects, nor does it include the use of
osseointegrated implants.
Definition: Full mouth rehabilitation entails the performance of all the
procedures necessary to produce healthy, esthetic, well functioning, and selfmaintaining masticatory mechanism.

3

INDICATIONS FOR OCCLUSAL REHABILITATION
The reasons for undertaking occlusal rehabilitation may include the restoration
of multiple teeth, which are missing, worn, broken-down or decayed.
Increasingly occlusal rehabilitation is also required to replace improperly
designed and executed crown and bridge work. In certain circumstances
treatment of temporomandibular disorders may also be considered an
indication for rehabilitation, but great caution is advisable in such cases.
Regardless of the clinical reason, the decision to carryout any treatment should
be based upon achieving oral health, function, esthetics and comfort, and
treatment should be planned around these rather than the technical possibilities.
If these goals are to be achieved certain biological considerations are necessary
when planning and carringout occlusal rehabilitation. They are
1. The indications for reorganizing the occlusion
2. The choice of an appropriate occlusal scheme
3.

The occlusal vertical dimension

4.

The need (or otherwise) to replace missing teeth

5. The effects of the material used on occlusal stability control of parafunction
and TMD
The indications for reorganizing occlusion:
When undertaking relatively small amounts of restorative treatment, for
example up to two or three units of crown and bridge work, it is often
acceptable, and it is often advisable to adopt a confirmative approach that is to
construct the restoration to conform with the patient's existing intercuspal
position.

4

The alternative strategy is to reorganize the occlusion by establishing a new
occlusal scheme around a stable condylar position. The condylar position
usually chosen is termed "centric relation' (CR).
The decision to re organize a patient's occlusion may be made on the grounds
either that the existing IP is unacceptable and needs to be changed, or where a
very large amount of treatment is to be undertaken and the operator has the
opportunity to optimize patient's occlusion. The decision should (and can) only
be made after a detailed and careful examination of the occlusion, preferably
with the use of accurate study casts mounted-in a semi adjustable articulator in
the retruded arc of closure. Mounted casts should allow the discrepancy (slide)
between CR and IP to be analysed as vertical, horizontal and lateral
components both at tooth and condylar level. Moreover, adjustments can be
tried and potential restorations waxed allowing the feasibility and difficulty of
reorganization to be judged properly.
It must be borne in mind that jaw movement will be simulated only partially by
any type of articulator. Nevertheless, the semi adjustable articulators are an
invaluable supplement to diagnosis and can save time with occlusa!
adjustments when restorations are fitted.
Reorganization maybe considered when the existing IP is considered
unsatisfactory for any of the following reasons:
Repeated fracture or failure of teeth or restorations:
Clinical experience suggests that persistently failing restorations (for example
crown and bridge debonding) are very commonly attributed to unfavorable
occlusal loading which may be improved by reorganization. Bruxism:
An optimally constructed occlusion will better be able to deal with the forces
generated in parafunction.

5

Lack of interoeclusal space for restoration:
Reorganising the occlusion to eliminate a large horizontal component of slide
between CR and IP can create a valuable interoeclusal space for the restoration
of worn.anterior teeth. Alternatively, the occlusion may be reorganised at an
increased vertical dimension necessitating occlusal coverage for at least one
arch.
Trauma from occlusion:
This may be soft tissue trauma (due to teeth impinging on the cheek or alveolar
ridge) or periodonlal trauma (due to excessive or aberrantly directed occlusal
forces) the latter may have an accelerating effect on periodontal disease
although the evidence is conflicting. Reorganisation of the occlusion to direct
forces axially and eliminate interferences and premature contacts can reduce
tooth mobility. However, the overall gain in periodontal attachment is marginal
and should be considered as no more than adjunct to periodontal management.
Unacceptable function:
Poor tooth to tooth contact with tilting and overeruption of teeth may create
problems with masticatory function, particularly when large number of teeth
have been lost. Unacceptable esthetics:
Alteration in the clinical crown height may be necessary to improve esthetics,
and this may be made possible by constructing the restorations to a reorganised
occlusion, possibly at an increased vertical dimension.
The presence of TMD: The link between the occlusion and TMD is
controversial.

6

Reasons for Full Mouth Rehabilitation:
The most common reason for doing full mouth rehabilitation is to obtain and
maintain the health of periodontal tissues.
Clinical periodontal findings are correlated with radiographs to determine the
extent and character of any disease findings must then be correlated to function
of the mouth in examining the function of the mouth, many factors must be
considered. The most important factor is discrepancy known as the "premature
contact" a contact between an upper and lower tooth that prevents or interferes
with the normal path of closure of mandible. The area that receives the force of
closure after the patient "skids" off the prematurity may relate to a greater
degree of disease. This area receives the force in the form of a rebound as the
normal path of closure is interfered with by the premature contact.
The various excursions of the mandible must be examined to determine how
much harmony exists between the jaw movement and the tooth contacts, and
the teeth that receive most of the load in the different positions should be noted.
A definite correlation between the malfunction and the clinical periodontal
findings is usually possible. This correlation generally precludes all other
potential causes of the pcriodontal condition. Even so, in order to attack the
problem from every conceivable angle, we must consider and investigate each
of the other factors.
In conjunction with malfunction, we must consider oral habits that could have a
bearing on the condition present. These may include such things as bruxism.
lip-chewing, thread-biting, tongue habits, and soon.
Temporomandibular joint disturbance is another reason for full mouth
rehabilitation. This may be difficult to diagnose, and great care must be taken
to determine the etiological factors involved. Frequently, there is a poor

7

relationship between the articulation and the movements of the joint -a
disharmony of function. Sometimes there is a muscular dysfunction that is
caused by some irritant or a nervous affliction. This muscular dysfunction may
be caused by the poor articulation, which produces muscle spasms, and these in
turn may be interpreted as a joint disturbance. In joint cases, the periodontal
condition is usually very good, which is probably why the joint has been
injured instead of the periodontium. When a disharmony exists, we must
ascertain whether the patient is injuring his joint as a result of malfunction, a
bad habit, or an emotional disturbance. Emotional disturbances are very
difficult to deal with and often require the assistance of a competent
psychiatrist.
Still another reason for full mouth rehabilitation is the need for extensive
dentistry. In such cases, some teeth are missing, others are worn down, and
there are old fillings that need replacing. Usually, the patients have little
periodontal involvement and no joint symptoms. These are the easiest cases to
treat, and the beginner should limit his or her full mouth rehabilitation to them.
As long as extensive dentistry is necessary, why not work on the case as a
whole so that ail the parts will be related to each other and to the function of
the individual?
By far, the most difficult patients to treat are the few who have succeeded in
developing a severe periodontal condition as well as a malfunctioning joint.
Even though the joint may be asymptomatic, it may exhibit a behavior pattern
that is troublesome to deal with. It may be mobile, and the dentistry may
require frequent adjustment as the joint begins to function properly with
possible heaiing. In addition, tooth settling and migration will increase the
discrepancies. These are the cases that try men's souls, they require one to
proceed with extreme care and to anticipate the possible contingencies.

8

Sometimes it is impossible to predict the extent of treatment necessary in order
to resolve the condition.
The treatment of the emotionally disturbed patient with a joint probiem is
probably the most exasperating. Although it is possible to treat the condition
physiologically, the emotional disturbance is another problem. Patients
with beautifully functioning masticatory mechanisms may still be able to
produce joint symptoms almost at will. It is unpleasant to have to suggest
psychiatric treatment, but if the dentist is convinced that this is the problem,
then he owes it to the patient and to himself to recommend such a course.
Which Patients Should Not Be Treated by Full Mouth Rehabilitation?
Frequently, friends and relatives of one's rehabilitation patients will request
similar treatment. There are many malfunctioning months that do not need
extensive dentistry and have no joint symptoms. These cases are best left alone.
Some mouths that have the potential to break themselves down, never actually
produce the destruction, for some reason. We are not justified in prescribing a
full mouth rehabilitation unless there is definite evidence of tissue breakdown.
One may argue, as many have, that it should be undertaken as a preventive
measure. But there are many malfunctioning mouths that do not break down,
proving that we cannot predict such things. If there is need for extensive
dentistry, then by all means it should be carefully correlated to the rest of the
mouth by complete rehabilitation. Some times one or two "good" teeth may
have to be operated on in order to satisfactorily accomplish our objective.
Ideally, dental procedures should be directed toward the prevention of such
conditions: in short, no pathology -no treatment.

9

THE GOAL OF FULL MOUTH REHABILITATION
History
The modern practice of renewing and reorganizing (he teeth by prostheses
began with the idea of'raising the bite" to rectify closure resulting from
excessive wear of the occlusal surfaces. Later, such closure was associated with
hearing loss, noted by Costen. This view, though later questioned, served to
stimulate interest increasing the length of the patients own teeth and thus in
increasing the vertical dimension.
In correcting articular disturbances, the best procedure came to be the retention
of the remaining natural teeth in so far as this was possible. To accomplish this,
these teeth were rebuilt to harmonize with the movements of the joints in order
to protect them from further injury.
With our present understanding of traumatic occlusion and its deleterious effect
upon the supporting structures, the procedure known as "bite raising" has
shifted in emphasis and broadened in scope and is now designated by a term
that describes it accurately. Full mouth reconstruction, jt now includes therapy
which will, by improving the relationship of the teeth, improve the condition
and health of the supporting structures.
When the teeth have been realigned through full mouth reconstruction, the
general tone of the supporting tissues invariably improves. What factors
account for this improvement? Obviously, the removal of excessive lateral
forces and the elimination of plunger cusps and similar forces attendant upon
the realignment of full mouth reconstruction lessen continuous injury to the
supporting structure. But these factors, though helpful in improving the
condition of these structures, are less important than the increased stimulation
of and circulation in the tissues that are brought about by the improved
function.

10

The masticating apparatus that is normal, healthy, and functioning is able not
only to carry out the work for which it is designed, but also to maintain itself in
health. The various structures involved, through their form and arrangement,
provide for both the synchronization of, and mutual protection against, all
forces. When function is good, a generous blood circulation furnishes the tissue
with the elements needed to keep them in a healthy condition. When function is
disturbed by malocclusion, the relation between the mutually protective parts
of the masticating apparatus is disrupted; moreover, because of lessened use,
blood circulation is diminished.
As indicated by O'Rourke, the force of a persons masticatory muscles remains
fairly constant. It is the use of the force that changes under conditions of
traumatic occlusion. The patient's ability or willingness to use his muscular
force is dependent upon the comfort, or absence of pain, he experiences each
time he brings his jaws together.
Mutilated mouths with chronically inflamed supporting structures, due to
traumatic occlusion, will support very little force without producing some
discomfort. The result is continuous subnormal use of, or at best failure to
make vigorous use of, the teeth and jaws. The vascular tissues of the
periodontium can be stimulated only by the teeth in function. Such stimulation
is lacking when this function is impaired by the inability of the patient to use
the musculature in chewing because of the tenderness of these tissues.
The results, in the words of Merritt, "are" atrophy of the alveolar process,
malocclusion of the teeth, dental caries, impacted and missing teeth,
periodontal lesions, and so on. Unfortunately, subnormal function lower vitality
at the same time that it increases susceptibility to disease.
Patients who have had full mouth rehabilitation commonly say that their
mouths feel "stronger". The masticatory muscles have obviously not been

11

strengthened by therapy. What has happened is that out patients can exert
greater force with comfort and without anticipation of pain than they could
before and that therefore they do exert greater force.
The therapeutic benefit of improved tooth arrangements and improved
functioning have been indicated. The individual patient's reaction bears witness
to these benefits and should inspire us, in terms of human satisfaction as well
as of scientific progress, to strive continuously for improvement in the
techniques of full mouth rehabilitation.
It should be kept in mind that although the operations of all mouth
rehabilitation procedures are performed on tooth units, they have one basic
objective: the equalization of the forces directed against the supporting
structures. Any disharmony at the occlusal or incisal aspects of a tooth will
direct forces against these malaligned surfaces and thus subject the supporting
structure to traumatic injuries. Similarly, any impairment of buccal or lingual
harmony will be reflected in injury to the gingival tissue and subsequently to
the deeper tissues involved in supporting the tooth. The proximal contact
anatomy is also vital in maintaining the health of the underlying soft tissue.
Poor contact relationships encourage food impaction with resultant periodonlal
tissue loss.

12

ANATOMY AND PHYSIOLOGY OF THE MASTICATORY
MECHANISM
An understanding of the anatomy and physiology of the masticatory
mechanism is essential to intelligent diagnosis and adequate treatment. If we
know, how the normal masticating mechanism functions, we will be able to
recognize its malfunction and be, in a position to correct it. A correlation of the
anatomy of the parts and the function of the parts will help one understand the
intricacies of the mechanism.
The Osseous Structures:
The masticating mechanism is primarily made up of three osseous structures:
the temporal bones, the maxillae, and the mandible. The maxillae and the body
of the mandible house the teeth -the instruments of mastication. The temporal
bone and the condyle portion of the mandible form the contact or articulation
between the osseous structures of the mechanism. In addition, the muscles that
activate, the chewing mechanisms obtain their anchorage from and are attached
to these osseous structures. Continuous contact is made between the mandibles
and the temporal bones by means of the temporomandibular joints. The glenoid
fossa of the tempoial bone is concave antero-posteriorly as well as
mediolaterally. It is the shape of the anterior slope of the-fossa that determines
the condyle paths (lateral, protrusive, and lateral-protrusive). The head of the
condyfe is oval in shape, with its long axis at an oblique angle to the median
axis of the skull. The synovial membranes and the meniscus are inter-posed
between the fossa and the condyle(fig-l).
In function, the head of the condyle rotates on the undersurface of the
meniscus. It is in this compartment of the joint that the hinge-like action of the
joint takes place. The hinge-like action is the center of action of the parts: the
disc, the condyle head, and the synovial membranes. The upper surface of the

13

disc makes contact with the articular eminence of the glenoid fossa. It is the
simultaneous sliding of the disc and condyle that produces the translatory
movement of the temporomandibular joint. In other words, the head of the
condyle rotates on the undersurface of the disc the condyle and the disc
together translate in the fossa (anteroposteriorly, mediolaterally, or inbetween).
The meniscus, or disc, consists of fibrocartilage, which is oval in shape and
thinner at the center than at the circumference. "The inferior surface is concave
and Fits on to the condyle of the lower jaw; while its superior surface is
concavoconvex from before backward, and is in contact with the articular
surface of the temporal bone" (Morris. 1933).
The stress-bearing character of the disc is evident in the fact that ihe blood and
nerve supply is in the periphery, the center being devoid of these tissues.
Contact between the head of the condyle and the articular eminence is made by
the cenier of the disc. The stress of mastication in the joint is absorbed in this
relation. The meniscus has its bearing against the articular surface of the
temporal bone(fig-2), which forms the anterior wall (articular eminence) of the
glenoid fossa. It is in this relationship that the forces of mastication are
absorbed by the temporomandibular joint.
Lubrication of the joint is accomplished by the synovial membranes. Each
compartment of the joint has its own synovial sac.
The disc and the synovial membranes are neither compressible nor variable in
the normal course of events, but serve as ball bearings between the skull and
condyle.
Function of Ligaments and Muscles:

14

Ligaments and muscles hold the temporomandibular joint and the chewing
mechanism together. The ligaments limit the amount of movement of the
mechanism and prevent the mechanism and joint from falling apart when the
muscles are relaxed.
They help to determine the position to the mandible when the muscles relax:
thus, to some extent, physiological rest is govcrneu by these ligaments.
The most important ligaments of the temporomandibular joint are the capsular
and the temporomandibular. The temporomandibular ligament forms the lateral
part of the capsule and reinforces it. The upper part of the ligament is broad and
is attached to the zygoma and to the tubercle (articular eminence of the
zygoma). It is inclined downward and backward and is inserted into the
condyle and neck of the mandible laterally(fig-3). The fibers coming from the
tubercle are short and nearly vertical. Together, the capsular and
temporomandibular ligaments enclose the structures of the joint and tend to
limit its1 movements. Sphenomandibular and stylomandibular ligaments are the
two accessory ligaments that protect the joint during wide excursions (fig-4).
These ligaments are loosely attached in the upper compartment of the joint to
permit translator;' movements. They are more firmly ' attached in the lower
compartment where the hinge-like action takes place. The temporomandibular
joints are movable fulcrums activated by the muscles of mastication. These
joints have some of the elements of a ball and socket. They glide forward and
backward as well as sidewise. Actually, they can glide and rotate at the same
time in the manner of a movable ball and socket.
Muscles of mastication:
In a discussion of the muscles of mastication, there is a tendency to speak of
individual muscles and describe I heir separate actions, but muscles function in
groups as kinematic chains. The Temporalis Muscle:

15

The temporal is muscle is a large, strong muscle of mastication. It has its origin
in the temporal fossa on the side of the skull. Its origin covers a considerable
area and. by means of an aponeurosis, it connects with its mate on the other
side of the skull very much in the manner of a saddlebag. Its insertion is in the
coronoid process of the mandible and reaches down to the ramus of the
mandible

should

be

noted

that

the

insertion

is

anterior

to

the

temporomandibular joint. Although the fibers of the temporal is muscle are
described as vertical, oblique, and horizontal, contraction of any or all of these
fibers has a definite tendency to elevate and relrude (he mandible. This is
understandable if we recall that the temporomandibular joint is made up of the
glenoid fossa, the anterior surface of which slopes upward and backward, and
that the meniscus is interposed between the head of the condyle and this slope.
Any contraction of a muscle attached in front of this upward slanting guide
must have a tendency to brace the condyle head in a posterior and superior
position(fig-5).
The Masseter Muscle:
The masseter muscle has its origin in the zygomatic arch. It arises in two heads:
a superficial one from the outer border of the arch, and a deeper one from the
inner and more posterior portion of the arch. Its insertion is in the outer angular
region of the mandible. Fibers of the masseter muscle are almost at right angles
to the occlusal surfaces(fig-5).
The masseter is a very powerful muscle of mastication. Its contraction elevates
the jaw and forcibly brings the teeth together. Like the temporalis muscle, its
contractions tend to seat the condyle in a posterior-superior position in the
glenotd fossa. Neither the temporalis nor the masseter has anything to do with
lateral movements of the jaw. Their contractions primarily elevate the jaw and
bring the teeth together. It is because of this action that the occlusal surfaces of
the teeth must harmonize with the hinge-like action of the mandible. The

16

masseter can snap the teeth together in any position from centric to protrusive.
Having the occlusal surfaces of the teeth in harmony with this action permits a
better dissipation of the forces of this muscle to the periodontal tissues of the
teeth as they come together through a bolus of food.
The External and Internal Pterygoid Muscles:
The external and internal pterygoid muscles are responsible for the lateral
movements of the mandible. The external pterygoid has its origin, by means of
two heads, in the great wing of the sphenoid bone and the outer surface of the
pterygoid plate. The uppermost fibers of this muscle are inserted in the articular
disc through the articular capsule. The majority of the remaining fibers are
inserted in the anterior surface of the neck of the mandible.
The fibers of the external pterygoid muscle are in a horizontal and medial
direction, and their contraction pulls the head of the condyle and the meniscus
forward and medially. This action sets the mandible into position for chewing.
If the external pterygoid on one side relaxes while the one on the other side
contracts, the mandible will be moved into a lateral position. It guides the
mandible into lateral position and steadies it while the subject bites (contraction
of the temporal and masseter) in the lateral position, Contraction of the fibers
of the external pterygoid also tends to act as a brake against the posterior pull
of the temporalis muscle. It effects a muscular balance against any violent
jamming of the head of the condyle posteriorly(fig-6).
The internal pterygoid muscle originates from the palatine bone and the maxilla
and from the internal surface of the pterygoid plate. Its fibers are inserted in the
lower part of the inner surface of the ramus of the mandible at the angle. They
run laterally, downward, and backward(fig-7).

17

Neuro-Muscular Coordination:
The various structures and individual movements just described are
coordinated by a complex integration of the nervous function. During
mastication, sudden contact of a tooth with a hard object produces discomfort
and reflexively opens mouth. This is called a nociceptive reaction and is
partially responsible for protecting the chewing mechanism when there are
premature contacts in the articulation.
Reciprocal Inncrvation:
The nociceptive reaction is able to protect the mechanism because of the
phenomenon known as reciprocal innervation. This is the simultaneous
activation of a flexor reflex and the inhibition extensor (stretching) reflex, and
vice versa.
Rhythmic chewing is made possible by the efficient reciprocal innervation of
the masticatory muscles as they alternately depress and elevate the lower jaw.
During mastication, proprioceptors in the muscles, tendons, and joints send
messages through afferent fibers in the trigeminal nerve to the chief sensory
nucleus of this nerve. Secondary fibers cross the brain stem, ascend to the
thalamus, and finally arrive in the sensory cortex via tertiary tracts. In this
manner, awareness of motion in the jaws and of the position of the mandible in
relation to the maxillae during chewing movements is permitted. Some
proprioceptive impulses pass from the chief sensory nucleus to the cerebellum,
thence through a chain of neurons to the motor cortex. The motor cortex is thus
informed of the position of the teeth and jaws. and its action makes possible the
synchronous mastication movements. Motor activity, whelfter reflex or
voluntary, demands little conscious effort: so it becomes necessary to have all
the parts of the masticating mechanism working in harmony with each other to
prevent its self-destruction.

18

Movements of Mastication:
The masticatory movements of the mandible are automatic and occur under
considerable force. Mastication begins with the incision of a morsel of food: To
accomplish this, the mandible is dropped open by the contraction of the
external pterygoids and the infrahyoid and digastric group of muscles. If the
external pterygoids contract equally (which is improbable), the patient will
execute a straight protrusive movement. More likely they will contract
unequally,

and

a

lateral protrusive position will be assumed. Now the

incisor teeth have to be propelled through the food to cut it, and this is
accomplished by the contraction of the elevators of the jaw: the lemporalis,
masseter, and internal pterygoids.
After some food has been grasped, mastication proceeds. The bolus is
propelled into the mouth by the lips, tongue, and checks and probably is rolled
onto the bicuspids, which cut it up further with the crushing and shearing action
of their blades. The temporalis and masseter muscles partially relax allowing
the food to be replaced on the chewing surfaces. The external and internal
pterygoids are in a state of alternate relaxation and partial contraction, and the
temporal is and masseter again contract to crush the food some more. By this
time, and after several strokes, the bolus has reached the molar teeth, where
now it will get a final milling before is swallowed. The masseter and temporalis
muscles relax; the external and internal pterygoids on the same side contract
while those on the opposite side relax, thus cocking the mandible in a lateral
protrusive position. The food is now repositioned on the occlusal surfaces of
the molars, and the real power of mastication is applied by the masseter,
temporalis, and internal pterygoid muscles. As the masseter and temporalis
muscles contract and crush the food, the alternate contractions of the internal
pterygoids cause a wiping of the lower occlusal surfaces of the molars across

19

the upper occlusal surfaces in a finely triturating action that comminutes the
food preparatory lo swallowing.
More specifically, if the bolus of food is on the lower right first molar and
ready for its final comminution, the temporalis and masseter muscles on both
sides relax. The external and internal pterygoids on the right side relax; the
external and internal pterygoids .on the iefi side contract and cock the mandible
to execute a working occlusion on the right side. Now the temporalis and
masseter muscles on both sides contract forcibly to crush through the food. The
external pterygoid on the left side relaxes, permitting she mandible on the left
side to return home. As the condyles both approach centric position, the
internal pterygoid of the right side contracts, executing the Bennett movement.
The masseter and temporalis on the right side soon relax, permitting the followthrough of the masticating stroke as the external pterygoid on the right side
contracts.
It must be remembered that during all of the jaw movements the condyles and
menisci are moving together. Again we must emphasize the harmonious
relation of the teeth to these movements that should exist if the investing
structures are to be protected from destruction.
Harmony of Form and Function:
Because of the complexity, automation, and force fullness with which the
chewing cycle is executed, it should be apparent that a high degree of harmony
must exist between the form and function of the 'parts. Although nature has a
buiit-in safety device in the proprioceptive reflex mechanism, repeated insults
in the form of a premature contact may impose the learning of a new reflex
pattern. It may not be as effective as it should be, and soon the additive trauma
will begin to take its toll. Then too, with advancing age the sharpness of the
protective reflex is lost, and more and more damage is done to the mechanism.

20

Protection by Proprioception:
It is interesting to note that the protective proprioceptive reflexes operate best
during normal function. The self-protective mechanisms are weak or missing
during non functioning movements. It has also been shown that reflex activity
is reduced during sleep, with the nonsecretion of the parotid gland. The
protective proprioceptive reflex apparently fails to function during bruxism.
This is one reason for correcting the malocclusion of patients who practice
bruxism, for while it may not cure the habit, it will minimize the damage that is
done.
Up to now we have attempted to briefly outline the chewing movements and tc
describe the anatomy of the masticatory mechanism. Very little has been said
about the teeth, the chewing implements: but we have implied that a harmony
of form and function is necessary.
The objective of maintaining the health of the structures of the mechanism is of
prime importance. To accomplish this, we strive to prevent any part of the
mechanism from overworking or being abused. A certain amount of work has
to be done in the form of chewing. For the moment, let us disregard any bad
habits and consider only the normal use of the apparatus to masticate food.
A certain amount of muscular force is necessary and available. How that
muscular force is dissipated by the various components (the joints, teeth, and
investing structures) is of extreme importance. For instance, if, in the chewing
cycle previously described, a single tooth came into contact before the others,
what would be the result? As the patient penetrated the food bolus, the
premature tooth would receive all the muscular force exerted after penetration
of the food. This force in turn would be transmitted to the periodontal tissues
and in time would cause their destruction.

21

By harmony of form and function, then, we mean an equal distribution of the
forces of mastication that will permit the periodontal tissues of all the teeth and
the stress-bearing portion of the joints to equal) absorb this muscular force.
Equal distribution of the functional forces over as much tissue and as great an
area as possible will guarantee the health of the entire mechanism: this is the
objective of our treatment.

22

THE HINGE AXIS
The successful application of the hinge axis in dentistry was the greatest single
contribution of the Gnathological Society. It was the cornerstone of all future
accomplishments and still is the basis for articulation.
The hinge-like action of the temporomandibular joint has been described by
anatomists for over a hundred years. Its application to dentistry, however, had
to wait for the Gnathological Society in the 1920s. Prior to that, Snow, Gysi,
and others had been aware of the presence and importance of an opening and
closing axis. Yet their methods were so crude that they concluded that the axis
was somewhere below the condyles. This inaccuracy led them to believe that
changing vertical dimensions was still a chair operation.
The desirability of being able to reproduce the opening and closing component
of jaw movements on an articulator must have been evident. That they were not
able to accomplish this was the fault of the methods used and the fact that there
was no articulator that could duplicate this movement. The Gnathological
Society developed a means of attaching a face-bow rigidly to the mandibular
teeth. This permitted accurate location of the opening and closing axis. Many
refinements in equipment were, of course, -necessary to make this a practical
procedure. For example, easy adjustment of the caiiper points was a "must."
After it had been clinically demonstrated that there was a usable hinge axis, it
became necessary to design an instrument that would duplicate this component.
The articulator had to have an intercondylar axis that could be aligned with 'he
axis located on the patient.

23

Definition of the Hinge Axis:
What is the Hinge Axis?
The head of the condyle rotates on the undersurface of the meniscus. While it
rotates on the-meniscus, the meniscus and condyle can move on the surface of
the articular eminence. The movement can be forward, to the side, or anything
in between. While the meniscus and condyle are thus translating, the condyle
can execute a pure hinge movement anywhere along this translation.
Consequently, mandibular movements appear to be very complicated and
confusing. It is practical to locate the center of vertical motion; it is also
practical to locate the center of lateral motion. The center of vertical motion
and the center of lateral motion are one and the same -the center of rotation
-and there is one in each condyle.
The hinge axis is an imaginary line connecting the center of rotation of one
condyle to the center of rotation of the other condyle(fig-8). The vertical
opening and closing movements, as well as the pure lateral movements
originate from the centers of rotation. Any combination of vertical and lateral
movement has its center in the same point. The center of rotation of each
condyle is constant to the condyle, and therefore to the mandible. The hinge
axis (the imaginary line joining these centers) then is constant to the mandible
(and teeth). As the mandible moves in its various excursions, the hinge axis
moves right along with it. The mandible is capable of executing a hinge-like
closure in any position(fig-9). This is one reason why the hinge axis is so
important. It permits us to duplicate all the arcs of closure of the mandible on
an instrument and thus tailor our cusps to harmonize with these arcs.
One point of confusion about the hinge axis stems from the method of locating
it. It is located in the rearmost position of the mandible - the terminal hinge
position. It is located in this position because only here can it be repeatedly

24

separated from the other components of jaw motion. The patient, of course,
does not function in this terminal hinge position. We purposely make him
execute a terminal hinge closure so that we can locate the center. Once it is
located, we endeavor to trace the path of this center to enable us to duplicate
every possible combination of the two movements (rotation and translation)
that the patient will use in function.
By determining the hinge axis and transferring it to an articulator, it is possible
to make casts of the mouth (teeth) in the exact dynamic relationship to each
other that exists in the patients head. Only by use of the hinge axis is it possible
to have teeth approach each other on an articulator exactly as they do in the
mouth. The hinge axis permits us to have the vertical dimension under our
control on the articulator and to duplicate all the eccentric relations and all the
possible contacts of the teeth in these relations. We can study and diagnose
tooth relations thoroughly; confident that they are exactly as they exist in the
patient's mouth, and we can return our work (whether dentures or natural tooth
reconstruction) to the instrument for correction with knowledge any changes in
vertical relations will be harmonious when placed in the patients mouth. It is
only by means of the hinge axis (and centric relation) that the teeth can be
related accurately to the terminal hinge position.
The Hinge Axis and Centric Relation:
To secure a centric interocclusal record, we attempt to "freeze" the terminal
hinge closure at a convenient opening. Without the hinge axis, we would be
unable to secure an accurate centric interocclusat record because to obtain such
a record, the recording medium must not be penetrated by the teeth or the
occlusion rims. (The implication is that the mandible would deviate because of
the guidance of the penetrating teeth or rims). In order to avoid penetration (at
least in dentulous cases), we must obtain centric interocclusal record in an open
relationship, and if we were not on the same arcs of closure, our efforts would

25

be useless. It is impossible to check a centric inlerocclusal record without an
axis mounting.
Technique for Locating the Hinge Axis (fig-10):
The location and transference of the hinge axis are not very difficult
procedures, but they must be carried out with great care because they form the
foundation for many other procedures. A convenient type of facebow is used. It
must be rigidly attached to the mandible so that it actually forms an extension
of the mandible.
A reference plate or clutch is cemented to the lower teeth with Truplastic.
Graph-lined flags are placed on the side of the face over the condyle areas to
eliminate any skin movement distraction. These flags may be attached to the
maxillae by means of a crossbar and a maxillary clutch, or they may be held in
place by a head frame or other contrivance. A crossbar is attached to the lower
reference plate or dutch.
Adjustable side arms are placed on the lower crossbar with the styli in the
vicinity of the condyles. The patient must now be instructed in the hinge-type
of movement. As previously indicated, this is not a normal movement for the
patient it is for our convenience only. The patient must be coached to let his
mouth drop open. This necessitates the relaxation of the external pterygoid
muscles, and some patients may have difficulty in comprehending this
movement. It helps sometimes to have the patient place his hand on our chin as
we demonstrate the type of relaxed opening and closing desired.
Possible Need for Bite Plane Therapy:
If a patient has difficulty in executing a pure hinge movement, it may be
necessary to train him in This abnormal opening and closing movement.
Training can be accomplished by using the jig.

26

In some cases where joint pathology may be present it may be necessary to
have the patient wear a bite appliance of some kind to disclude the teeth and
allow the joint to return to a more normal condition. Three or four days will
usually suffice, but sometimes several months of bite plane therapy may be
required. The patient must be carefully monitored during any extended period
of wearing a bite appliance for tooth movement.
The patient naturally opens downward and forwards a combination of rotation
and translation. We must separate the rotation from the translation so that we
can locate the center of vertical opening. In addition, this opening and closing
must be accomplished in the terminal hinge position, for here we can get
repeated concentric arcs that will permit us to locate their center. Any other
arcs will serve only to confuse the issue, at this point. What we actually have is
a compass with bent rigid arms. The pivoting part of the compass is on the
center of rotation in the patient's condyle. The stylus point is the tracing part of
the compass. If we succeed in getting the tracing point exactly over the
pivoting point, there will be no arcing of the tracing point. Geometrically, if we
had two concentric arcs, and if we erected bisecting perpendiculars to the
chords of these arcs, they would intersect at the center of the arcs(fig-11).
However, there is no practical method for making such a plot. The trial and
error method first used by Dr. McCollum is still the only practical way to
locate the axis.
When we succeed in getting the patient to execute a rhythmic opening and
closing in the terminal position and the stylus point is arcing, we visualize
where a center would have to be for scribing such an arc. Thus, we will have an
idea of which way to move the stylus in order to reach the center. After making
an adjustment in this direction, we try it again. As we approach the center, the
arcs will become smaller and a little more opening will be required to magnify
the arc. After several adjustments, we will be close to the center. A magnifying

27

glass should now be used to help us see whether there is still any arcing of the
stylus tip. The graph lines will aid the eye in determining this. By viewing
down one line and then down the crossing line, we can see whether there is any
slight arcing. If there is, we continue adjusting until it disappears completely.
We must learn to distinguish between the pure hinge movement and the
movement with some translation. The patient will inadvertently make a
translatory movement every third or fourth try. Some patients will
be most cooperative; others will be exasperating. Nevertheless, we must arrive
at an axis if the rest of the procedures are to be correct.
The axis center must be located on each side. What we arc locating is the hinge
action on the side of the face. It is a point on the hinge axis and not the actual
center of rotation. The actual center is approximately 10 or 11mm medial to
this location. Consequently, the location of this point must be made as close to
the skin as possible. This means that the flag must be very close to the skin
(fig-12).
Marking the Axis Location on the Patient:
When we are satisfied that we have located these points on the axis, we remove
the flags from the patient. A marking medium, such as an indelible pencil, is
rubbed on the end of the stylus. We make sure the patient is in the terminal
hinge position and then have him move his head out of the headrest, making
sure that he does not also move out of the terminal hinge position. The stylus is
gently pushed against his face to transfer the paint to the skin. These marks are
made permanent by using a special needle and a little pink marking dye
-sulfide of mercury (fig-13).
In all of our subsequent transfers we must try to simulate these conditions -the
skin in the same relaxed position and the stylus pins locked the same distance
from the face as they were before the flags were removed. This is usually 1/16

28

of an inch from the skin. By doing so, we reduce to an absolute minimum any
possible error in transference. In addition, the stylus pins must be locked and
not moved until the mounting is completed. The articulator has to have an
intercondylar axis that can be extended to these points so that the transfer is
accurately lined up with the axis of the machine.
Selection of a Face-Bow:
From a purely theoretical point of view, an ordinary face-bow such as a Snow
or Hanau can be used to locate the hinge axis. To attempt to use either one of
them in actual practice, however, is impossibility. It is a bit more practical to
use one of these bows as a transfer instrument, provided the styli are perfectly
lined up one to the other. As a matter of fact, if the styli are perfectly lined up
and we are able lock the bow by means of the universal joint in front so that the
points of the styli are on the axis locations then it will not be necessary to have
an articulator with an expandable intercondylar axis. Under these
circumstances, it is possible to bring in the styli pins an equal degree towards
the intercondylar axis of the articulator and still stay on the axis. However, it is
far easier and more accurate to use a fully adjustable face-bow (i.e.. one with
arms that can be independently adjusted by means of micrometer screws) for
both the axis locations and transfers.
By means of a face-bow transfer and the mounting frame, the upper cast can be
properly mounted to the axis of the patient.
The Hinge Axis and the Plane of Reference:
The hinge axis is constant to the mandible, as has been indicated. The terminal
hinge position, which is actually the centric relation, is constant to both the
mandible and the maxillae. All our mountings are made in this relation.
Therefore, the only practical way to maintain constant relationships throughout
treatment is to use the axis points and a fixed third point at the base of the right

29

orbit as our plane of reference. Thus, the axis orbital plane gives us a constant
position for the upper jaw, and a correct centric interocclusal record will
establish the position of the lower jaw to the constant upper jaw. In this way,
repeated mountings will have a constant, relation to our records and to the
patient's centers of rotation.
Discussion and Conclusion:
Many have attempted to find fault with the hinge axis and to disprove it. Their
criticisms cover such things as skin mobility, change of the axis, the
introduction of errors by moving the stylus tip a slight degree, and the presence
of a separate axis for each condyle.
Actually, skin mobility is reduced to a minimum by the precaution of having
the patient move his head out of the headrest when all references are made to
the marks. Any changes that might occur over the years from loss of weight
and the like would be minor. As far as change of the axis is concerned, the only
changes observed have been in the joints with some pathology.
If a patient has a painful joint, or if a patient does not execute a hinge-like
closure after a few guided opening and closing movements, it would be
desirable to do one of two things: either train the patient with the jig as you do
when getting a centric relation record, or put the patient on a bite plane for
several days. This will usually relieve the pain and give a smoother hinge-like
movement.
If there are symptoms in a temporomandibular joint, there may be some slight
change in the axis location. Always plan to relocate the axis on such patients a
year or two after the pathology has cleared up.

30

Why use the hinge axis in these cases?
The answer is simple: it is still the only means of establishing a starting point to
which we can repeatedly return and to which we can definitely relate our work
as it progresses. In every normal joint case that we have rechecked over the
years for demonstration purposes and to satisfy our own curiosity, we have
always been able to relocate the axis within very acceptable limits, that is, by
the thickness of the tattoo mark.
The most ridiculous criticism is the charge that error is introduced because the
stylus pin has to be moved through the thickness of the card covering the face.
A Single Transverse Axis:
The allegation that there is a separate axis for each condyle is mumbo-jumbo.
The anatomy and physiology of the joints would not permit a two-axis
arrangement.
About 1950, Dr. William Branstad, Dr. Raymond Garvey, and Dr. Robert Okey
conducted an experiment to determine whether there was one transverse axis
through both condyles or an axis for each condyle. They found that there was
one transverse axis. Dr. Arne Lauritzen, working with a study group, repeated
the same experiment about 1957 and arrived at the same conclusion. Dr. Frank
Celenza and V.O.Lucia repeated the experiment during the summer of 1959,
with the same result. In the fall of 1959, the Hinge Axis Committee of the
Greater New York Academy of Prosthodontics repeated this experiment and
concluded that there was only one transverse axis through both condyles.
This, in brief, was the experiment:
Clutches were cemented to the patient's teeth. A crossbar, 36 inches long, was
attached to the upper clutch, and another of the same length was attached to the

31

lower clutch. Four graph-lined flags were attached to the, upper bar for the
purpose of accurately locating the center of rotation(fig-14).
One flag was placed on each side of the face, close to the skin. The other two
were attached near the ends of the upper bar, about 12 inches from the Hags
against the face. Attached to the lower bar were four adjustable side arms, to be
used in locating the center of rotation. Each side arm was placed against a flag.
The center of rotation was located in each of the four areas, that is, each side
arm was adjusted against its corresponding flag until there no longer was any
arcing, but only rotation of the stylus point. When all four centers of rotation
had been accurately located and the patient was held in centric relation
(terminal hinge position), the cards on the flags were carefully marked with the
tips of the styli. The upper bar with flags attached was then removed from the
clutch. With a fine, heated instrument, a tiny hole, was burned through each
card where it had been marked. When the four flags were held up to the light, it
was possible to see the light through all four flag holes, proving that the four
points had to be on a straight line(fig-15). Thus, it was concluded that there was
only one transverse axis.
To demonstrate this more emphatically, we set up the bar and flags and with a
small penlight passed rays of light through the four holes. The camera at the
other end of the four flags recorded the light rays coming through the four
pinholes. In addition. a piece of dental floss was threaded through the holes.
When pulled taut, it was perfectly straight. This was conclusive proof of the
existence of only one transverse hinge axis.
The existence of a usable hinge axis component to the temporomandibular joint
movement is one of the greatest luxuries that we could have when treating the
oral mechanism.

32

Proof Positive of a Usable Hinge Axis:
On a patient whose axis was located, we proceeded to take centric relation
records at increasing vertical dimensions and compared them with a split cast
mounting. An accurate set of casts was made of the patient's teeth. The upper
cast was prepared for a split cast to accurately examine the likeness of the
various records. The
CENTRIC RELATION
Centric relation means many things to many people: to some, it means the
contact of teeth after a jaw closure; to others, it means a closure in a particular
position, the particular position having many interpretations, varying from an
habitual closure to a forced retrusion, or somewhere in between. Still others
identify it as the most retruded position from which right and left lateral
excursions can be made. Some dentists refer to centric relation when they are
talking about the mandible, disregarding the teeth depending upon their belief
and understanding, they decide that the mandible is in centric position, and that
if the teeth occlude in this mandibular relation, then the teeth are in centric
relation. Other dentists describe "mandibular centricity" as a mandible-tomaxillae relationship at a certain vertical dimension. It is unfortunate that
centric relation means so many things to so many people, because no other
phase of dentistry is as important as a clear understanding of centric relation.
Obviously, it should have one and only one connotation to the dentist.
To understand centric relation and to appreciate its great importance, we must
understand how the jaw functions. We must set about to make restorations that
will function normally in that jaw: they must neither interfere with nor force a
particular action on the chewing mechanism. In other words, the restorations
must fit into the pattern of jaw movements: they should follow, without any
detrimental effects, the movements of the masticating mechanism. Our present

33

concern is with the type of motion, how it takes place, and its bearing on the
all-important subject of centric relation. This, of course, directs our attention to
the temporomandibutar joint. For the moment, we may forget about the ether
important structures -the muscles, tendons, ligaments, nerves, blood supply,
and teeth and confine our consideration to the action of the temporomandibular
joint.
Location of the Centers of Rotation:
It is possible to demonstrate beyond any doubt that there exists a recordable
center of vertical rotation in the condyles. An imaginary line joining these
centers has been termed the hinge axis.
In practice, when we locate the point on the side of the face for the hinge axis,
we are actually locating the hinge action in the facial plane (on the side of the
face).
This is not the true center of vertical motion, however, for that is located in the
condyle. What we are locating is a point on a line-that has been extended from
the centers of vertical motion. In other words, the point we locale on one side
of the face is on the same line passing through the actual centers of vertical
rotation in each condyle and through the point on the other side of the face. For
this reason, when making a transfer, we must not move the points of the stylus
in or out once we have located the point of hinge action. In practice, we must
have a means of transferring these hinge- action points to a suitable articulator,
the intercondylar axis of which can be lined up with these points. This is
accomplished with the mounting frame.
We can locate the centers of hinge action only when the condyle is in a position
where it can repeatedly perform the hinge action. Because patients normally do
not execute a hinge action in the most retruded position of the mandible, they
must be educated to this movement. When we consider this, as well as the

34

many habits patients can acquire over the years and the conditioned reflex
action forced by habits and tooth relations, it is easy to understand why some
patients reluctantly produce the hinge action during treatment.
This hinge action (and the imaginary line called the "hinge axis") is constant to
the mandible. In other words, the vertical motion of the mandible (and
condyles) is produced by the action of the heads of the condyles on the
undersurface of the meniscus. Thus, as the condyle and the meniscus translatemove down the incline of the glenoid fossa or across the trough of the fossa in
the Bennett movement the mandible can produce this hinge-like action in any
position of the condyle. As a matter of fact, it will start to produce a hinge-iike
action as it glides down or across the condyle path. We must remember that the
hinge action is constant to the meniscus in any position in which it may find
itself, but it is constant to the maxillae or fossae only when the condyle is
executing the hinge action in the terminal position..
In addition to the centers of vertical (opening and closing) motion of the
mandible, there exist centers of lateral rotation: The patient can make pure
lateral movements that have centers of rotation located in the condyles. At one
time, there was considerable confusion about these centers because they are
seldom stationary. In other words, the centers themselves move as the mandible
(condyle) is making the movement. The-path of these centers of lateral rotation
on the rotating or working side is the Bennett path. The confusion arose
because it was claimed that the center of lateral rotation was some where in
back of each condyle or in the vicinity of the foramen magnum. The moving
centers of lateral motion were called "loci." Actually, what was termed the
center of lateral movement behind the condyies or "somewhere else" was the
center of the locus. The center of the path that the center of lateral movement
was making on the working side was, in fact, the center of the Bennett path. It
is practical to locate the exact centers of lateral rotation by means of two gothic

35

arch tracings taken in the same plane in front of each condyle and on either side
of the midline of the face and reproduce their path across the fossae (fig-16).
When this has been done in conjunction with the location of the centers of
vertical rotation (hinge action), then we have truly found centric relation. The
terminal hinge action is the vertical component of centric relation; the centers
of lateral rotation are the lateral components of centric relation. Why this is
centric relation, we shall now attempt to explain. We shall also show why. it is
so important.
It might be stated categorically that unless we locate the centers of rotation, we
are disregarding centric relation. This statement will immediately draw protests
because, regardless of one's understanding of centric relation, all will agree that
centric relation is essential to the practice of dentistry and cannot be ignored.
Let us analyze what really happens:
In the course of constructing occlusal surfaces for dentures, bridges, or natural
teeth, we take a centric interocclusal record, using the material of our choice.
The casts on which the restorations are going to be fabricated are mounted on
some sort of instrument, and the case is constructed.
In order for a centric interocclusal record to be usefui, it must register the
maxillomandibular relationship without any tooth contact or tooth penetration
of the recording medium. If tooth surfaces contact through the recording
medium, we can be sure that the proprioceptive reflexes have crossed us up and
caused us to record an improper relationship.
It is apparent that one of two things must be done even to begin to get an
accurate interocclusal record either it must be secured at the exact level of
vertical dimension without tooth contact (a nice trick if it can be
accomplished), or else the casts must be mounted on the articulator to the same
opening axis that the mandible has to the maxillae of the patient. If the latter is

36

done, then the centric interocclusal record can be secured in an open position to
clear the tooth contacts; and when the registering medium is removed, the teeth
on the casts can be approximated as they are in the mouth.
It is also most desirable that we check our centric mounting because many
hours of laboratory work will depend on this relationship. It is utterly
impossible to check a centric interocclusa! record accurately unless hinge axis
procedures and transfers have been used.
In order to check a centric intcrocclusal record, it is necessary to take a second
record, using all the care taken with the first one. It would be pure chance if the
second record were of the exact thickness as the first. The wax might be softer,
or the patient might close further. Whatever the reason, chances are against our
getting records of exact thickness. Yet, unless we were on the same arc of
closure on the articulator as in the mouth, the thick ness of the two records
would have to be absolutely identical.
The seating of a wax interocclusal record on casts can be quite deceptive. The
second record might appear to fit between the casts without causing any
malposition of the articulator parts. However, if we really want to determine
whether our two centric interocclusal records are identical, we must resort to
the following procedure frequently demonstrated in the clinics of Dr. Arne
Lauritzen
The Split Cast Technique:
Before mounting the upper cast on an articulator, second section (the split cast)
is carefully prepared. First, it is very important that the upper cast be poured
with extreme accuracy, care being taken to avoid any bubble formation. The
mounting side the upper cast is trued up on a model trimnifr. "V'notches are cut
on the edges of the mounting side of the upper cast -two in front, two on the
sides, and one in the posterior region. These notches are carefully made so that

37

they are truly wedge shaped. A piece of electrician's tape is wrapped around the
periphery of the cast, producing a form into which the second section of the
split cast is poured. Prior to this pour, the cast has been carefully lubricated
with Kerr Separating Medium. Three knobs of stone are placed on top of the
pour to serve as handles in the separation of the disc from the original cast. In
pouring the disc, it is extremely important to prevent any bubbles from
forming. When the disc pour has hardened, the cast is separated from the disc
by removing the electrician's tape and using the stone knobs on the disc as a
handle. Immediately after separation, the two parts are reassembled to prevent
any dust or loose fragments of stone from adhering lo the contacting surfaces.
The knobs are now cut down with a model trimmer, leaving just enough of
them to engage the new mix of stone that will be used to fasten the disc and
cast to the upper bow of the articulator.
An impression (whether it is for a study cast, a master working cast, or a
remount cast) is poured in stone. The excess stone is vibrated into the plastic
mold groove former and quickly inverted and placed on top of the poured
impression. Press it into place as you center and level the former. Do not invert
the impression. When the stone has set, remove the former and replace it with
the ring mold and secure it with periphery wax. Lubricate the grooved stone
with a separating solution and vibrate a mix of stone of a different color into
the ring mold. Level the surface with a spatula and place several knobs of
excess stone for retention when mounting to the articulator. Remove the ring
'after the stone sets and separate the impression. Trim the sides on ? model
trimmer and you are ready to mount it on the articulator by means of the facebow transfer.
By means of a face-bow transfer, the upper cast and disc are accurately
attached to the upper bow of the articulator. By means of our centric
interoccltisal record, the lower cast is next attached to the lower bow of the

38

articulator. This completes the mounting of the split cast and the lower cast in
what we believe to be a centric relation.
If we now open the articulator, separate the disc from the upper cast, press the
upper cast into the centric interocclusal record to be sure it is accurately seated
in place, and then attempt to close the upper bow and disc into the "V" notches
on the upper cast, we will soon find out whether: our mounting was accurate. If
it is satisfactory, we proceed to check this mounting and interocclusal record
with the second record taken. The first wax record is replaced by the second
one; the upper cast is seated into the indentations; and again an attempt is made
to close the disc into the "V" notches of the upper cast. It is amazing how often
an apparently acceptable interocclusal record is inaccurate. This technique
should be ample proof that a centric interocclusal record cannot be accurately
checked unless the hinge axis and hinge transfer procedures are used.
If these procedures are as far as we go, the restorations constructed on such
casts will come together accurately in centric closure. If we add one more step
and reproduce a protrusive path with a protrusive record, it is possible to have
proper contacts in both the centric and protrusive relationships. Unfortunately,
though, patients do not chew only in these positions. .
How does a dentist manage without using the axis and a protrusive record?
Like the dentist who simply takes a static closure, by proceeding to do a great
deal of work in the mouth, grinding here and there until some surfaces come
together. Considerable work is involved for an inferior result.
The dentist who takes a hinge-closure record, relating it properly to an
instrument by means of a face-bow, and then takes a protrusive record is only
slightly better off because there are all the laterals to contend with. Even if one
believes that the patient does not use his lateral excursions, the fact is that he
will use them if he is permitted to. The apparent shortcuts -not locating an axis,

39

not reproducing all of the patient's movements are responsible for the creation
of flat, useless occlusions. To avoid these headaches, we must locate the
centers of rotation. In addition to locating the hinge axis and obtaining a proper
centric interocclusal record, we must locate the centers of lateral rotation. This
is accomplished by means of the twin gothic arch tracings. Moreover, we must
trace the paths of these centers of lateral rotation. This is done with an extraoral tracing device, the pantograph: the pantograph is the only practical means
of accomplishing this today. With the pantograph, we can trace the protrusive
paths of the centers of rotation, as well as the right and left lateral paths. From
the pantograph tracings made by the path of travel of the centers of rotation, we
can reverse the procedure and duplicate the centers and their paths on an
articulator capable of full adjustment. Now when the restorations are
constructed and placed in the mouth, they will be in harmony with the patient's
movements. It will not be necessary to grind them, with the resultant
destruction of proper function.
To recapitulate: A thorough understanding of centric relation is essential 10 the
proper practice of dentistry. However, unless we locate the centers of rotation,
we are disregarding centric relation, which entails the following:
1. Location of the hinge axis
2. Location of the centers of lateral rotation
3. Transference of the casts to the axis
a) Face-bow transfer of the upper cast to the axis
b) Relation of the lower cast to the upper by a correct centric interocclusal
record.

40

Obtaining Centric Relation - Various Materials for Various Situations
Methods of manipulation for centric relation:
1. One handed technique by Anderson and Tanner (fig-16a).
2. Anterior stop technique a) Lucia jig technique
b) Leaf gauge technique advocated by Long (fig-l6b)
3.

Central bearing point method (fig- 16c)

4.

Bilateral manipulative technique (Dawson technique fig-l6d) Methods for

taking centric bite records
l. wax bite procedures
2. Anterior stop techniques
3. Use of preadapted bases
4. Central bearing point technique.
The technique for obtaining a centric relation is secondary to an understanding
of the phenomena. Various materials will produce acceptable results, but the
important thing is to know what we have to get and to be aware that we have
what we want.
From our preceding discussion we know that we must locate the centers of
rotation. By means of the two gothic arch tracings we are able to locate the
centers of lateral rotation, and by means of the hinge axis location we are able
to locate the centers of vertical rotation. Our practical problem now is to couple
these two centers of rotation into the center of rotation. To do this, we must
relate the lower jaw to the fixed member, the upper jaw. Having related the
upper jaw (cast) to the center of vertical rotation by means of the face-bow and

41

having set the articulator for the centers of lateral rotation, it now remains for
us to orient the lower jaw (cast) to these centers.
We accomplish this by "freezing" the lower jaw (cast) in the terminal hinge
closure at a convenient vertical dimension. This is the problem of obtaining
centric relation. There are many factors that complicate this procedure; and
patience and experience are required to complete the task satisfactorily. Among
the complicating factors are the patient's reluctance to make a pure hinge
closure; the patient's neuro-muscular pattern, which may have developed
around a deflective occlusal contact; the natural tendency of many patients to
go into a physiological rest position at the completion of any jaw movement;
and the natural tendency of a patient to exercise his prehensile reflex whenever
anything is placed between the teeth.
Certain procedures and materials are required lo overcome these factors. The
very first procedure is to practice with the patient until he is able to execute a
pure hinge closure. Second, we must block out some of the neuro-muscular
reflexes by preventing the teeth from coming together. We can accomplish this
by using our thumbnail as a controllable anterior stop. Third, we must keep the
patient under function, swinging up and down so that he cannot go into
physiological rest. As long as the jaw is functioning, its bracing position is
maintained. The natural prehensile reflex can be minimized if we have the
patient close his eyes during these procedures. If he sees the wax wafer (the
recording medium) approach his mouth, he will automatically begin to reach
out to grasp it with his teeth; and this is not a centric closure. We must take
care not to violate these precautionary procedures as we make our recording.
This presents quite a problem because what is really needed is a magic material
-a material that by its lack of resistance will not cause any unequal
displacement of the joint or teeth; a material that will remain sufficiently soft

42

long enough to ensure a dynamic registration, but will "freeze" just as soon as
all the procedures are completed.
Two-Stage Registration:
One method that has proved acceptable is a two- stage registration. A wafer is
made of one sheet of DeLar wax and one sheet of Tenax wax. These are luted
together. The reason for using two kinds of wax is to permit an easy
indentation on one side and to provide a stiffer side that will act as a carrier.
The wafer is placed vertically- in a water bath at 138°F. The anterior part is
kept out of the water so that it will remain stiffer and offer some resistance
anteriorly, thus ensuring the bracing position of the condyles.
While the wax is softening, the patient is rehearsed in the terminal hinge
closure. The patient is instructed to open and close his jaw without clenching
his teeth together. By avoiding the tooth contacts, the patient does not receive
the pcriodontal proprioception that could cause an abnormal reflex closure.
This is what we are trying to avoid: we desire a pure hinge closure free of any
"acquired" malpositions. This procedure will help the patient to execute a pure
hinge closure. It permits the temporomandibular ligament to be extended to its
normal position. It trains the patient to separate the rotation from the natural
combination of rotation and translation that makes up all functional
movements.
The patient is rehearsed in the terminal hinge closure while the cheek retractors
are in place. These conditions will simulate the actual taking of an interocclusal
record. The patient is instructed to close his eyes, and when the wax wafer is
sufficiently soft on the Tenax side, it is inserted into the mouth, with the Tenax
side against the upper teeth. The patient is told to swing his jaw several times
without closing on the wax, and then when we can "feel" the terminal hinge
closure, lie is instructed to close lightly against the wafer. At this stage we are

43

chiefly interested in getting an accurate imprint of the upper teeth in the Tenax
wax(fig-!7).
The wafer is removed from the mouth and placed in water of room
temperature. After partial chilling, it is trimmed to the outside edges of the
tooth indentations to remove the bulk. We also remove the anterior portion,
cutting it off across the center of the cuspids. There is a twofold reason for
removing this part of the wafer: first, with the anterior teeth exposed, we can
use our thumbnail as the anterior resistance; and second, without the anterior
portion, there is that much less area to seat against the casts when we make the
mounting. Consequently, should there be a slight discrepancy in the anterior
part of the casts, it will not cause their malrelationship. In short, our only
concern will be with the posterior areas.
The wax wafer is now replaced on the upper teeth and held in place with the
thumb and forefinger of the left hand. It must be evenly seated against the
upper teeth. The patient is instructed to close into it again to correct any
warpage. The wafer is then removed, and with a Bard Parker knife4 we trim
away with the excess wax around the indentations on the Tenax side, leaving
only the cusp tip indentations so that the cast may be accurately seated when
we make our mounting. Again, we seat it on the upper teeth and have the
patient close once more to eliminate any warpage that may have resulted from
the trimming process. When we are satisfied that we have an accurate seating
of the wafer against the upper teeth, we proceed to complete the interocclusal
record.
We remove the wafer and dry it with a blast of compressed air. Taking a sheet
of AI u wax, we form a "pencil," melt it, and apply the softened wax to the
underside (DeLar side) of the wafer, dripping it on as if using a candle. Aluwax
melts at a lower temperature than DeLar or Tenax, and thus provides us with a
soft surface that can be easily carried to the mouth without warping the

44

wafer(fig-18). We place the wafer on the upper teeth, holding it in place with
our left thumb and forefinger. With our right thumb on the patient's chin, we
guide the patient into the terminal hinge closure.
During this procedure, the patient's eyes arc closed. We have him execute the
terminal hinge closure, but do not allow him to contact the softened Aluwax
until we are sure of the "swing." Gradually, we let him close more and more
after each swing until the Aluwax is contacted. It may be necessary to add wax
several times before we can obtain an acceptable interocclusal record(fig-!9).
The Tests of an Accurate Interocclusal Record:
There are several ways of determining whether an interocclusal record is
accurate.
1. We should hold the wax wafer up to the light to see whether there is any
penetration. If there is. it will not be correct. Likewise, if there are one or two
thin spots, the chances are that it is incorrect. Areas of penetration or thin areas
are likely to cause a slight deviation of the mandible -so slight that we may be
unaware of it. Variations of thick and thin spots will offer variations in
resistance and may cause as much inaccuracy as a penetration.
2. If the thickness is satisfactory, we place the wafer on the upper teeth and
carefully examine it to determine whether the seat is accurate. There must not
be any "give" in any area.
3. We have the patient close into the wafer, first guiding him as we did during
the taking of the interocclusal record and then allowing him to close by his own
muscular force. If there is a hesitation in finding the indentations, the
interocclusal record is probably inaccurate,
4. If the foregoing requirements are satisfied, there is one final test lo make:
we have the patient close into the wafer and hold it firmly; then we examine the

45

posterior portion for any play between the teeth. Both sides should be
examined carefully.
If the interocclusal record meets all these tests, we are justified in accepting it
as correct. This may seem to be a long and tedious procedure but bear in mind
that everything we have done previously and everything we do subsequently
will depend absolutely upon this one procedure. An error in some other part of
the operation may be tolerated but an error here is disastrous.
Up until 1961, the preceding technique was reasonably successful. We still use
this technique for a preliminary record, before locating the hinge axis.
In 1961 and 1962 the "jig" was developed. There was nothing new in the
principle of the jig. The late Ernest Granger used his thumbnail as an anterior
resistance. His analogy of taking a centric record to the driving of a golf ball
said a great deal. He described it. as an art -driving a golf ball well is not
accomplished by many. The late Steve Brown used a wax wafer with chilled
wax anteriorly to seat the condyles. Dr. Grubb and his technician, "Jonsey".
used a gold casting on the lower teeth to maintain vertical and centric relation
while they carved the restorations in the mouth. I am certain that Dr. Pete
Dawson captures the correct centric relation with his jaw manipulation
technique. Dr. Stuart uses a tongue blade for his anterior resistance.
The Jig Technique:
Constructing the Jig:
It is preferable to make the jig on an upper study cast. Some clinicians make it
in the mouth, but this can be dangerous because of the heat generated when the
self-curing plastic cures.

46

Block out any undercuts in the anterior teeth of the cast with wax. Adapt tin
foil over the anterior teeth of the prepared cast. Lubricate the tin foil with
petroleum jelly.
Make a mix of Dura Lay in a dappen dish. When the mix has a doughy
consistency, place it on the tin foil and adapt it labially and lingually over the
centrals. Labially it should extend just over the margin of the gums. Lingually
it can extend onto the palate about 1/2 inch. The sides are tapered to the lingual
'and extend to the distal of the two centrals. Occlusally, ihe surface is a flat
plateau, thick enough to have sufficient material to adjust and separate the
teeth. As the Dura Lay polymerizes, keep removing and readapting it so that
you have a well-fitting jig that can be removed from the model without
breaking the model.
The occlusal surface is not inclined -we don't want a wedge effect Some
dentists have used the jig as an inclined plane. This is absolutely wrong! The
wedge is one of the most powerful mechanical devices in existence. A wedge
can split a mighty oak. The jig used as a wedge can displace the
temporomandibular joint distally with great ease. The platform on the
mandibular surface of the jig is just that a platform against which the lower
anterior teeth will close. It acts as the third leg of a tripod -the other two legs
are the condyles. The platform (mandibular surface of the jig) must not
influence the direction of closure. It must not force the lower jaw to the right or
to the left- It must not force the mandible forward or backward. It just stops the
closure. A very, very slight posterior inclination will assist the patient in
holding this position while the recording material sets. Even in very deep
overbite cases, the contact area is a flat platform, not an incline.
When the jig has cured, we trim it as shown in(fig-20). The labial frenum is
cleared and the labial margin of the jig just goes beyond the tree margin of the
gums. It should fit onto the anterior teeth without being displaced.

47

Three wax wafers are prepared on the upper study cast. Use one sheet of DeLar
wax. Soften the wax in water and place it on the cast so that you can cut it to
proper dimensions. Have the wax extend about % inch outside the buccal
surfaces of the teeth. In the anterior region, cut out a "U" large enough to
accommodate the Dura lay jig
We are now ready to go to the patient. A DeLar wax wafer is softened in water
at 1380 F. The wax wafer is placed in the mouth and the patient is guided into a
closure (hopefully somewhere near centric relation). Before the wax solidifies,
bend the corners of the wax over the labial of the cuspids{fig-21). These “ears"
will serve to reposition the wafer after we cover the indentations with the zinc
oxide and eugenol paste that we will use later. The indentations will be covered
with the paste and will not help us to reseat the wafer in the same position in
which it was imprinted. The "ears" will help us to reseat it in the same place as
when it was formed. The three wafers are so prepared.
Now we are ready to train the patient with the jig. This is one of the important
functions of the jig-to break the patient's habitual closure. It prevents the teeth
from reinforcing together, and thus it prevents the teeth from reinforcing the
reflex act of closure. It short-circuits the proprioception that directs the engram
of closure. Therefore, it is essential that the teeth are not allowed to come
together during the training process. If they did contact, the reflex act would be
reinforced and we would defeat our efforts. A piece of carbon paper is placed
between the mandibular surface of the jig and the lower anterior teeth. The
patient is instructed to move to the right, move to the left, move forward, and
move backward. This has the tendency to free the jaw movement. The jig is
removed and the patient is prevented from bringing his teeth together by
placing a saliva ejector in his mouth. The jig is reduced in thickness with an
abrasive rubber wheel. There usually is a gothic arch traced on the jig. Remove
the tails of the gothic arch and slowly reduce the apex -the area of lower

48

tooth contact. This is area is ground flat -not inclined. The procedure is
repeated again and again until the vertical is reduced, but there is still ample
intcrocclusal space. This should be continued for about 20 minutes. When you
are finished, place one of the wax wafers between the teeth, and with the
patient closing firmly against the jig, the wax wafer must still be free to be
moved up and down between the teeth. There must not be any contact between
the teeth and the wax. When we take the zinc oxide and eugenol wash, the
wafer should literally be floating between the teeth. In this way, there is no
conduction of stimuli from the upper teeth to the lower teeth.
We are now ready to take our final registration. The teeth are lubricated with
petroleum jelly. The jig is secured on the anterior teeth with denture adhesive.
A mix of Temp Bond or a bite registration paste is made and applied sparingly
on the indentations of the wax wafer on both sides. The wax is sandwiched
between the paste. Do not use too much paste. Place the paste-covered wax
wafer in the mouth using the "cars" to seat the wafer on the upper teeth. The
patient is guided into a hinge closure and instructed to hold this position firmly.
The patient is closing firmly against the jig. Hold your thumb on the patient's
chin with the index and middle fingers cradling the undersurface of the
chin(fig-22). This will enable you to know if the patient relaxes before the
paste sets. Keep reminding the patient to close firmly. This will place the
condyles upward and on the posterior slope of the articular eminence -a
position that most believe to be the correct position for the heads of the
condyles.
The record is carefully removed after the paste has set. In order to avoid
warpage, a simple procedure is followed. The thumbs of both hand* are placed
on the patient's 'chin, and the index fingers are placed on the outer edge of the
wax record. The patient is instructed to gently separate his teeth. The wax

49

wafer is braced against the lower teeth -the lower jaw acts as a form. Then the
patient is guided into closure again. Now the thumb and index fingers of the
left hand are placed to support the wafer against the upper teeth, and the patient
is again instructed to gently separate his teeth. The upper jaw now acts as the
form to prevent the wafer from being distorted. The wax wafer is removed
from the mouth and chilled. With a pair of surgical scissors (those with a
serrated jaw to grab the set paste), the excess paste is removed. All we want are
the cusp tip indentations so that we can accurately seat the casts into the wafers
and see if they are perfectly seated. The trimmed wafer is returned to the mouth
(with the jig in place) and the patient is guided into centric relation closure.
This will correct any possible slight warpage that could have taken place in the
removal and trimming. The two other wafers are treated the same way. After
the third record has been taken and trimmed and reseated, we remove the jig
and again guide the patient into centric closure (this time with out the jig).
Remove the third wafer "and don't allow the patient to close. Insert each of the
other two records, one at a time, and have the patient close into them (guided)
without the jig in place. The records are now completed and we arc ready to go
to the laboratory and make our mounting and check our centric relation
records.
There are some considerations for special situations. When taking a centric
relation record for working (master) casts, it is necessary to use several
thicknesses of wax for the record. The reason for this is that because of the
increased interocclusal space after tooth preparations, the paste will not register
the tips of the preparations unless the space is reduced by means of the thicker
wafer. In other words, the paste will not stand up long enough to capture an
imprint.
In a remount record, a single wax wafer is sufficient, because now the
restorations are in place and the interocclusal space is reduced. When anterior

50

teeth are missing, you might have to make a Duralay bridge. Your own
ingenuity is your only limitation. When posterior teeth are missing, you may
have to make a Forma Tray wafer with cones to contact the soft tissue in very
small areas. A little thought will allow you to handle almost any situation.
In the laboratory, the upper cast with the split cast wafer is attached to the
upper bow of the articulator, related by a face-bow transfer. A centric relation
record is used to relate the lower cast to the lower bow of the articulator. When
the mounting in completed, we are read;' to verify our results.
Open the articulator separating the two halves of the split cast arrangement.
Make sure the centric relation record is satisfactorily seated between the upper
and lower casts, and close the articulator. The split cast should come together
perfectly. This assures a correct mounting. Next we must verify the centric
relation records. Remove the record used for mounting the lower cast and
replace it with one of the other records. Again, make sure of correct seating of
the casts in the record and close the articulator. The split cast should go
together as it did with the first record. Repeat with the third record. If ail three
records check out the same, there can be no doubt about the accuracy of the
centric relation you obtained.
The Jones Bite Frame:
Another method of taking an interocclusal record is with the Jones Bite Frame.
After the patient has been "trained" with the bite jig. the recording is made with
a zinc oxide and eugenol paste, taken in a gauze "sandwich." This is a rather
tricky, but accurate, procedure. A Jones Adjustable Bite Frame is used to carry
gauze strips. These are glued to a thin wire insulation known as "spaghetti" in
the radio trade. The insulation tubes with the gauze strips attached are cut into
1 1/2 -inch lengths. These are slipped on the wire frame, which is adjusted

51

according to the size of the patient's jaw. This is best done on a cast of the
upper jaw.
A zinc oxide and eugeno! paste, such as Opotow's Mandibular Paste? or Kerr's
Registration Paste is used. The mixed paste is placed on the surface of the
gauze, and the gauze, which is about 3 inches long, is wrapped around the
outside wire of the frame and then around the inside wire until there is no loose
end. In other words, the gauze, with paste on its surface, is wrapped around the
buccal and lingual wires of the frame. This neatly wraps the paste between the
gauze and between the buccal and lingual wires. A slight amount of paste may
be applied on the upper and lower surface of this roll, on both sides of the
frame. It will take a little practice to learn to manipulate the paste without
becoming entangled in it.
The patient is retracted, after being trained with the jig, and the loaded bite
frame is inserted between the teeth. The patient closes firmly against the jig
until the paste sets (fig-23). The lower jaw is supported by your thumb and first
two fingers to ensure against patient relaxation. The set gauze "sandwich" is
removed and carefully trimmed (fig-24), This record is used tc accurately relate
the lower cast to the upper cast. It is best used to remount procedures where the
actual restorations are involved.
VERTICAL DIMENSION
A simple rule to help us determine the vertical dimension of occlusion on
patients with natural teeth is: do not change the vertical dimension of occlusion
that the patient has when the teeth are intcrcuspated in maximum contact.
Another rule that can be used with natural teeth to keep out of trouble is: do not
open the bite.
Bite raising refers to increasing the vertical dimension of occlusion. It is usual!;
done for one of the following reasons:

52

1. To relieve a temporomandibular joint syndrome
2. To restore "lost" vertical dimension in a severely worn occlusion
3.

To get rid of facial wrinkles

None of these reasons is valid:
Opening the vertical in each of these situations is an invitation to problems. U
is almost always contraindicated. Some facts should be understood about each
of these problems before any treatment is considered.
Bite raising for temporomandibular joint syndrome:
The vertical dimension has nothing to do with temporomandibular joint
syndromes. The pain-dysfunction syndrome can be solved at any vertical
dimension up to the point of condylar translation and down to the point of
coronoid impingement. As long as the condyles are free to go to their terminal
hinge position, the syndrome can be relieved.
Correcting the occlusion at an increased vertical may eliminate Lhe joint pain
but it almost always results in depression of the teeth, instability of the
occlusion, and excessive stresses on the periodontium. Besides, the
temporomandibular joint syndrome often recurs as the teeth shift under the
added stress.
Restoring "lost" vertical dimension:
More study is needed, put much clinical evidence indicates that even severely
worn occlusions do not lose vertical dimension. Restoring "lost" vertical
dimension in a worn occlusion really amounts to opening the bite because wear
does not normally produce a loss of vertical dimension. Patients can wear their
teeth down to the gum line and still not lose vertical dimension, because the
eruptive process matches the wear to maintain the original vertical dimension.

53

This process of eruption and alveolar development may continue throughout
life as teeth are worn because of the continual addition of layers of cementum
on the root and concurrent passive vertical development of the alveolar process.
So even with wear the jaw-to-jaw relationship remains the same when the teeth
are together.
Opening the bite to eliminate facial wrinkles:
On patients with natural opposing teeth, this procedure may have very
detrimental effects. When the masticatory and facial muscles are at rest, the
teeth should not be in contact. Increasing the vertical dimension to the extent of
stretching the wrinkles out puts such an unnatural demand on the stretched
muscles that It may actually accelerate further wrinkling. The increased length
of the teeth positions them in continuous interference to both normal
contracting and resting lengths of the muscles. Such continuous stretch
stimulation may cause reflex contraction of the muscles with damaging results
to the teeth and supporting structures. The stresses exerted on the teeth are
amplified by unfavorable crown root ratios that result from increasing the
length of the clinical crowns. Furthermore, the effect on the continuously
stretched muscle is to "age" it faster and produce worse wrinkles.
Patients who have previously had bite raising procedures to eliminate wrinkles
are often very insistent about further increases. As the teeth depress or the
wrinkles return, they express the need for more and more increase in vertical
dimension. Some patients tell us they were more comfortable when the bite
was first raised and they would like to regain that comfort. It is difficult not to
give in to such z request because it sounds so reasonable. If we understand that
their early comfort was the result of an improved occlusal relationship rather
than the increased vertical dimension, we can almost always regain the comfort
by equilibration without further increase of vertical dimension.

54

The patient must be made to understand that the muscles should be allowed to
position the jaw without interference from the teeth. "Support" from the teeth at
an opened vertical dimension constitutes an interference to the contracted
muscle in a normal power stroke.
Why not increase vertical dimension?
Occlusions get into trouble primarily from stress. The safest approach when
restoring an occlusion is to keep the teeth from interfering with normal muscle
activity.
When a muscle is neither hypotonic nor hypertonic, it is said to be "at rest".
Even resting muscle is in a mild state of contraction. This mild contraction of
antagonistic muscles is necessary to maintain the posture and position of the
bony parts. We cannot contract one muscle beyond its resting length without
affecting its antagonistic muscle to some degree. The antagonist must release
and give the contracting muscle its way or it may respond by isometrically
contracting more forcefully itself to counterbalance the effect of its antagonist.
Either way, the harmony of resting muscle is disturbed. Any restoration,
appliance or denture that interferes with the optimum lengths of the resting
muscles serves as a stimulus that produces hypertonicity. Such hypertonicity
may result clinically in destructive clenching or bruxism patterns.
Many years 'ago, Niswonger defined the rest or postural position as "that
position of the mandible in which it is involuntarily suspended by the
reciprocal coordination of the muscles of mastication and the depressor
muscles with the upper and lower (teeth) separated". He referred to this as a
neutral position of the mandible.
The rest position has often been a popular starting point for determining the
occlusal vertical dimension, but it is an unreliable approach because the
dimension between the rest position and occlusal contact is not a consistent

55

measurement for different patients. The rest position itself is not consistent.
Atwood found variations as great as 4mm, at the same sitting and even greater
variations at different sittings. Finding the vertical dimension of the rest
position and then arbitrarily closing a specific amount is a very unsatisfactory
approach.
If the occlusal vertical dimension can be established in harmony with the
optimum length of contracting muscles, the muscles will be free to rest at
whatever length is comfortable. The practical approach therefore is to
concentrate on accurately recording the occlusal vertical dimension and
allowing the freeway space to be the natural result of the difference between
the optimum length of contracted muscles and the length of the muscles at rest.
Stoneking has proposed that the definition for occlusal vertical dimension be:
"The vertical relationship of the dental arches when there is maximum
inlercuspation of the natural teeth, and the mandibular muscles arc contracting
through their maximum power cycle".
Some muscles may contract as much as 50% to 75% of their natural length.
Mahan has pointed out that the maximum force with which muscle resists
elongation is applied when it is completely committed to contraction.
It is also apparent that an increase in the vertical dimension would interfere
with the optimum length of contracting muscle in its power stroke.
Several studies have shown that there is a significant relationship between the
power point" of muscular contraction and repcatable phonetic and comfort
measurements. Tueller, using electronic means on dentures, found an average
variation of less than 0.5mm from the vertical established at the muscular
power point when compared with either preextraction records or phonetic
methods.

56

Silverman has reported consistent results in measuring the vertical dimension
of occlusion by phonetic methods. When a patient has lost natural occlusal
stops for recording the vertical, we have found that Silverman's closest
speaking technique has provided consistently reliable results. The vertical
dimension established in this manner is rcpeatable with extreme accuracy, even
over a period of months.
Phonetic method of measuring occlusal vertical dimension:
The phonetic technique is used when there are no opposing teeth in contact. To
understand the principle, one must perform the following steps, as outlined by
Silverman. on 8 patient with opposing teeth.
1. The patient is seated in an upright position with the occlusal plane parallel to
the floor. He is asked to close Firmly (centric occlusion), and a line is drawn
on a lower anterior tooth at the exact level of the upper incisal edge. This line
is called the centric occlusion line.
2. Now the patient says "yes" and continues the "s" sound like yessssss. While
he is pronouncing the "s" sound, a line is again drawn on the same lower
anterior tooth at the level of the upper incisal edge.

This line is called the

closest speaking line. The space between the lower centric occlusion line and
the upper closest speaking line is called the closest speaking space.
3. To analyze how repeatable this record is, the patient should be asked to
count from sixty to sixty-six. One should note how the upper incisal edges
comes right back to the closest speaking line with the pronunciation of each "s"
sound. If it does not, the line should be altered slightly to match the "s" position
when the patient reads or talks fairly rapidly.

57

4.

If such a measurement is to serve as a preextraction record, the difference

between the closest speaking line and the centric occlusion line is recorded.
The closest speaking space must be maintained in the finished denture.
5.

If the determinations are being made on a patient who has already lost his

natural occlusal

vertical

dimension,

the

missing

teeth

can

be

substituted for on temporary restorations or fabricated bases. After proper
lip support, esthetics, and incisal edge position have been determined, the
phonetic method can be used to establish the vertical dimension.

Since the

vertical dimension of occlusion is unknown, we determine the closest speaking
position first and then close the vertical 1mm from that point. A wax esthetic
control rim(fig-73) can be used in place of upper teeth, it can be attached to
the upper denture base and adjusted for lip support, smile line esthetics, and the
like.

If it interferes during the phonetic exercises, it can be easily corrected.

By placing several marks on the lower anterior teeth, we can note which mark
aligns with the incisal edge of the esthetic control rim or the artificial upper
anterior teeth when the S sounds are made(fig-74).
When normal phonetics function can take place comfortably, the closest
speaking level should be noted and the centric bite record should be made by
closing I mm further to the vertical dimension of occlusion.
Restoring extremely worn occlusions:
Excessive wear on upper anterior lingual inclines is most often the result of
posterior interferences that deflect the mandible forward. The forward
deviation of the mandible drives the lower incisal edges into the upper lingual
surfaces, and bruxism patterns may wear the surfaces nearly to the pulp. If we
observe the relationship of the teeth in centric occlusion, it will appear
impossible to restore the lost tooth enamel without opening the bite. If the

58

mandible is manipulated into centric relation, however, we will often find it is
somewhat posterior to the acquired worn position.
The interferences should be eliminated by selective grinding so that the
mandible can close without forward deflection to the same vertical dimension
as the acquired centric occlusion. When this is accomplished, we will usually
find that we have sufficient clearance between the lower incisal edges and
upper lingual inclines without changing the vertical dimension(fig-75).
It is not always practical, however, to restore a worn occlusion without some
increase in vertical dimension. As the anterior teeth wear, the lower incisors
have a tendency to drift forward. Severe wear may produce an end-to-end
relationship of the anterior teeth that is very difficult to solve. The problem is
intensified when the wear approaches the pulps of both upper and lower
anterior teeth. Sometimes the only choices open are either to devitalize several
teeth to make room for the restorations or to choose the alternative of
increasing the vertical dimension. The dentist must decide which decision is the
lesser of evils. The usual choice would obviously be to open the bite.
If the vertical dimension must be increased, it should be opened no more than
is absolutely necessary to provide room for the restorative materials. This
would rarely exceed 1 to 1 '/j mm. Even then, the dentist should be aware of the
potential problems that might result, mainly instability following the restorative
increase in vertical dimension.
When the vertical dimension must be increased, patients should be advised of
the possibility of some shifting of the restored teeth until the occlusion
stabilizes. Even an increase of lmm requires careful checking and periodic
occlusal adjustment for up to a year before normal stability of the occlusion
results.

59

When the vertical dimension is increased in combination with splinting, we do
not notice the same degree of shifting of the teeth.
Badly worn anterior teeth that have drifted into near end-to-end relationships
present a real restorative challenge. It is difficult to lengthen the upper anterior
teeth without severely steepening the anterior guidance, and patients who have
developed almost horizontal function do not readily change over to vertical
functional patterns. A compromise is usually called for that permits the anterior
guidance to start out as flat as possible and then progress into the steeper
guidance as gradually as possible by way of concave pathways.
By moving the incisal edge lingually we arc able to lengthen the lower anterior
teeth and provide some overjet for the upper teeth. Which we can produce
sufficient overjet, we can then curve down from the cingulum contact and
provide more length for the upper anterior teeth. Both esthetics and function
are improved by such a procedure.
Anterior wear is not always equal on both arches. There is no possibility of
cingulum contact in these cases so there is no good alternative but to have
contact on fairly wide upper incisal edges. Upper anterior teeth that do not have
fairly strong bone support may need to be splinted if the guidance is steepened.
Unless it results in labially directed stress on the upper anterior teeth, there do
not appear to be any problems associated with closing the vertical dimension
on natural teeth. It does not produce stress because a closed vertical dimension
does not interfere with muscle lengths.
Closing the vertical dimension to an extreme degree could cause coronoid
impingement against the zygoma, but it is highly unlikely that there would ever
be a need for that much closure. Tenderness to palpation in the zygoma area
would alert us to this.

60

Relationship of the anterior teeth to vertical dimension;
One of the most important considerations in any change of vertical dimension
is the direction of the arc of closure. As the mandible is elevated, the lower
incisors travel forward on the closing arc. Any time the vertical dimension of
occlusion is reduced, the lower incisal edges are automatically moved forward
at the more closed vertical dimension.
If the lingual surfaces of the upper anterior teeth are in the way of this forward
movement of the lower teeth, it results in horizontal stress directed labially
against the upper anterior teeth and lingually against the lower anterior teeth.
The axis of closure on most simple articulators is much closer to the occlusal
plane level than the true condyiar axis (which is higher). The arc of closure on
the erroneous "simple" articulators is nearly vertical, rather than forward, if the
bite is closed during restorative procedures, the interference to the front teeth is
not noticed on the improperly mounted models.
If such restorations are placed in the mouth. the resultant stress against the
anterior teeth is not easily picked up without digital examination. The incline
contacts are so steep and the vector of force is so horizontal that the upper
anterior teeth are forced out of the way and the lower anterior teeth are forced
inward. The result is continuous complaints by the patient that the front teeth
"hit too hard".
The vertical dimension can sometimes be closed to improve anterior
relationships in anterior overjet problems. Closing the vertical dimension may
arc the lower incisors forward into contact that they did not have al their
original occlusal vertical dimension.

61

FUNCTIONAL

ASPECTS

OF

COMPLETE

MOUTH

REHABILITATION
A BIOLOGIC AND FUNCTIONAL approach to restorative dentistry is
essential for the satisfactory performance and fulfillment of those requisites
basic to Prosthodontics. Accordingly, the masticatory organ must be considered
as a functional consolidated unit, with proper attention being directed to all the
elements that comprise this unit. All functional factors are interrelated, and
proper regard for each aspect is essential, if the restoration and maintenance of
the health of the entire functioning mechanism is lo be a realization.
Consequently, a comprehensive study and practical approach must be directed
toward the interrelation of the teeth and their supporting periodontal structures,
the myofunctional aspects of mastication, the intricacies of vertical dimension,
freeway space, centric relation, and centric occlusion.
The objective of complete mouth rehabilitation is the reconstruction,
restoration, and maintenance of the health of the entire oral mechanism. The
accomplishment of this goal requires an understanding and utilization of all
available dynamic potentials.
Complete mouth rehabilitation is a dynamic functional problem, and embodies
the correlation and integration of all component parts into one functioning unit.
The aim and endeavor, therefore, must be reconstruction and rehabilitation of
the whole satisfying all the related factors.
The science of complete mouth rehabilitation rests upon three proved and
accepted fund a mentals: namely, the existence of a physiologic rest position of
the mandiole. which is a constant; the recognition of a variable vertical
dimension; and. finally, the acceptance of a dynamic, functional centric
occlusion, These principles ha\e been basic in the development of the

62

myofunctional concept of mastication and have furthered the development of
the physiologic approach to occlusion.
Physiologic rest position:
Investigations have proved that the physiologic rest position of the mandible is
fixed and constant, and that it does not vary with age or with the presence or
absence of teeth. Thus, it is a reliable starting point for the design of a
physiologically correct occlusion. The physiologic rest position is a relaxed,
normal, physiologically balanced maxillomandibular positioning, wherein
antagonizing tensions that exist during function are in a state of equilibrium.
All functional movements of the mandible begin and end, at this rest position.
From a practical point of view, techniques have been devised whereby this
position can be recorded, registered, and maintained.
In order to study and determine mandibulocondylar changes that occur when
the mandible assumes the various functional positions common to it,
roentgenographic techniques for obtaining laminagraphs and cephalograph can
be adapted. The laminagraphic technique affords a means of comparative study
of mandibular positions and their respective, corresponding condyle
relationships. Exposures are made at the original tooth contact position, the
physiologic rest position, the wide-open position, and the proposed restorative
functional position. By a double exposure technique, laminagraphic
superimpositions are secured of the physical contact position and the
physiologic rest position of the mandible. Laminagraphy has proved a valuable
adjunct in temporomandibular joint radiography, for it offers a means of
securing undistorted, clear pictures of these joints. These studies enable one to
detect abnormalities of the articulating surfaces, deviations in the functional
pattern, and any gross pathology. It enables the dentist to gain a perspective of
the path of the condyle during closure, noting its displacement if any, as the
mandible travels from its physiologic rest position to its physical contact

63

position. It further enables the operator to observe the possibilities of
eliminating and correctirg this displacement by means of comparative study of
the mandibular positions. The size, shape, form of the condylar head and neck,
the fossa, and the aiiicular tubercle, tubercle, together with variances in the
condylar free-way space, may be observed in the superimposition of the
physical contact position and the physiologic rest position. Deviations and
changes from the natural will be observed in accordance with the particular
type of occlusal anomaly. Thus, this affords an opportunity of observing the
existing condyle positions, and offers a radiographic blueprint of the positions
that the condyles will assume at the completion of the restorative work.
Another important diagnostic aid in the recording and study of the mandibular
position is the cephalometer. The technique consists of positioning the head in
a fixed reference frame and of standardizing all the component, factors: the
central ray. The position of the head, and the x-ray film. Roentgenograms and
tracings of the successive positions of the mandible may then be obtained for
accurate comparative study. Exposures arc obtained at the physical contact
position, the physiologic rest position, and the proposed vertical opening. The
resulting cephalograms then may be superimposed, one upon the other, and a
composite tracing of the three mandibular positions can be obtained. This
offers a simple and concise means for comparative study, and affords a
blueprint of the exact amount of existing freeway space. The possibilities of
utilizing this potential freeway space in the rehabilitative process can be noted,
and it is possible to observe the functional freeway space that will exist after
rehabilitation. These methods of study are invaluable and act as a guiding
factor in the diagnosis and treatment planning by revealing the possibilities as
well as the physiologic limitations of treatment.

64

Functional analysis of occlusion:
A functional analysis of occlusion is pertinent to the formulation of a proper
plan of treatment for complete mouth rehabilitation. It must include: (1) The
determination of the proper vertical height by utilizing the physiologic rest
position of the mandible as a guide, and 'noting the existing functional freeway
space. (2) An examination and study of the path of closure from rest position to
the physical contact position of the teeth, noting whether condyle displacement
occurs. (3). The effects of the occlusal pattern upon the periodontal structures.
(4) A study of the temporomandibular joint positions relative to the occlusal
pattern by means of rocntgenographic evaluation.

65

TREATMENT PLANNING
Before we begin treatment, it is important to have a complete plan of operation.
The patient usually wants to know just what we are going to do. so that he may
plan his life accordingly. He should be told the probable length of time
involved in the treatment, the length and frequency of the appointments, and
the possible indisposition. A person in business may not want to return to his
office feeling numbness or discomfort after a two-hour session. He may
therefore prefer to have his appointment in the afternoon in order that he may
return directly home. Other patients would rather have the work done early in
the morning to get it out of the way. For the best dentist-patient relationship, all
these things should be considered.
Some patients have great distances to travel. We should plan their treatments
and appointments with a view to keeping the number of trips to a minimum.
Where patients come from out of town, our laboratory schedule should be
arranged so that the necessary work can be finished in a reasonable time.
In most cases it is advisable to give the patient a general outline -not the
particulars -of the planned procedure. The details will serve no purpose except
possibly to confuse, scare, or impress him. He will be more impressed,
however, by the results. Occasionally a patient is interested and intelligent
enough to want to know more about the projected work. In such instances, a
more detailed exposition of what is involved may help the general because of
patient education, since these patients may discuss the type of treatment with
their family and friends. In any event, it is extremely important that we outline
exactly what we plan to do.
Periodontal Treatment:
From our examination and diagnosis, we will have decided whether our first
course of action is to be periodontal treatment. Depending upon the case, this

66

may be extensive or conservative. Depending upon our personal judgment,
periodontal therapy may be postponed until the more important phases of
correct function are established.
A sensible procedure is to combine the periodontal treatment (if not too
extensive) with the appointment for the preparations. At this session, we
usually anesthetize one quadrant of the mouth. By the time the preparations are
finished, we have ample access to all the gingival tissues, and the interproximal
areas arc as accessible as they arc ever going to be. Deep scaling and curetting
is easily accomplished, and if any pockets are to be removed, they can be
quickly attended to. Mow often have we taken an impression that went beyond
(he margin and found an area covered with calculus? Now is the best time to
remove it. Furthermore, periodontal treatment (or curetting) will enable us to
get better gingival retraction at this time than we could other- wise obtain
without additional tissue trauma. Moreover, since we have to place temporary
coverage on the teeth anyway and cement it to place, this can be just as well
accomplished with a surgical dressing such as Ward's WondrPak. All we do is
to extend the dressing over the gingival tissues. This is recommended if the
periodontal condition is not extensive. If the periodontal treatment is
complicated, and is referred to a periodontist, then there are several ways to
proceed.
From the periodontist's point of view, it would be best to have the teeth initially
prepared and stabilized with temporary splints. These could be removed to
allow better access for the periodontal procedures. From the prosthodontist's
point of view, this means that the teeth have to be prepared twice. It is true that
with this sequence there is less likelihood of having margins of gold exposed
after tissue healing; on the other hand, it means double jeopardy to the pulps.
Every time a tooth is prepared, no matter how minor, the pulp is irritated.
Usually it recovers, and fortunately the time required for periodontal healing is

67

sufficiently long to allow the pulps to recuperate. In addition, the patient docs
not appreciate being assaulted twice.
Another way to proceed is to have all the periodontal treatment completed
before starling the tooth preparations. The periodontist has less access to the
areas, but usually he or she can manage. Any root resection can be performed
a! the time of periodontal treatment. The endodontic treatment can be
completed before or after root resection (for the remaining roots). Today, most
periodontisls are trained for minor tooth movement. If there is need for this
therapy, it can be incorporated at the same time that periodontal treatment is
being performed. Most prosthodontists can lake care of minor tooth movement.
However, if more complicated tooth movement is required to enhance a result,
then an orthodontist should be called upon to treat this phase of it.
The third way to proceed is to complete the prosthodontics and then have the
periodontist touch up the case. This is the least desirable, because there will
almost always be an esthetic problem.
As you must now be aware, we are recommending a very long tedious, painful
course.
From our examination and diagnosis, we should be in a position to recommend
one of several courses lo take. Some patients will not want (o go through
orthodontic therapy. These cases may have to be treated only by prosthetics.
even if there is some compromise in the end result Some patients may not want
to undergo extensive periodontal treatment: a compromise, with possible
deleterious results, may have to be made. There may be questionable teeth
involved. These questionable teeth may mean the difference between fixed
restorations and removable partial dentures. If the patient is set against a
removable appliance at this time, it may be necessary to use the questionable
abutment teeth, making sure that the patient is aware of the possible short life

68

of the restorations. Some patient are willing to take the chance in order to gain
a few more years of not having to wear a removable restoration. In these cases,
we may or may not build in contingencies for future changes in the restoration:
for example, precision attachments that could later be used for a removable
restoration.
It should be obvious that each case is an individual consideration. After an
honest presentation of all the factors, then the patient must make the final
decision. Don't try to insist on an ideal procedure for every patient, if the
particular patient will rot accept or cannot accept the ideal program. As long as
the patient understands all the possible problems due to the compromises, there
is nothing more that you can do. You may be amazed at the results cf cases that
are not given the ultimate treatment: many bifurcated and trifurcated teeth give
much more service than anyone expects: and many pockets of 2,3, and 4 mm.,
with proper home care and frequent office visits. do not get any worse for
many years.
When it all is said and done, there is one very important faci to remember: the
most perfect treatment possible will fail if the patient does not take good care
of it. This means excellent home care. A perfectly treated mouth that doesn't
get good home care will fail- it only takes a little longer. Treatment failures,
almost without exception, are with patient who are not sufficiently motivated to
execute good home care. The most intelligent people are often the most
disappointing: they seem to think that if they have paid a substantial fee for
something, it should take care of itself.
So. after a comprehensive diagnosis, and after evaluating the patient's altitude,
should be able to predict the course of events for each case.
In any event, the first part of treatment planning should encompass the soft
tissues. Any residual infections, abscessed teeth that cannot be salvage and

69

acute Periodontal pocket should be eliminated. Endodontics and possible root
resections should be executed.
Mandibular Registrations:
If registrations were not taken as part of the complete diagnosis, then they
should be taken now. This step must precede our decision as to the type of
restorations and preparations that will be necessary.
Clutches are to be constructed on the casts previously mounted for the purpose
of diagnosis, or reference plates are fitted to these casts. By means of the
pantograph, the patient's individual mandibular movements will be recorded,
and the pantograph registrations will then be transferred to a suitable
articulator. After adjustment of the articulator to the pantograph registrations,
the study casts will be remounted to the correct axis by means of a face-bow
transfer and a centric relation record.
It is advisable to have a duplicate set of study casts accurately mounted on the
articulator. Usually it is possible to pour a second set when alginate material is
used for the impressions. One face-bow transfer and one centric relation record
arc sufficient to mount both sets of casts. One set is preserved as a permanent
record of the pretreatment condition. The second set is utilized for making
temporary restorations, if they are to be used. In addition, the second set is used
in making the diagnostic preparations and diagnostic wax-up to determine the
type of preparations required and the amount of tooth structure to be removed
in each area.
Restorations:
At this point we plan our restorations.
With our knowledge of the principles of articulation and the development of an
articulation in wax. we proceed to survey the problem before us. Our study

70

casts now will duplicate the patient's relationship in every detail. The long a\is
of each tooth can be examined as it is related to the others in the various
excursions. The anterior overlap and overjet can be studied, and any changes
can be planned. Some orthodontic procedures may be indicated. The
buccolingual relationship of the posterior teeth is evident and will be helpful
in determining the type of restoration to be employed. The curve of Spee and
(he plane of occlusion are now observable in their true relationship to the oral
mechanism. Any changes in these conditions are planned before tooth
preparation begins.
The necessary cusps can be visualized or actually carved on the study casts.
This will dictate the amount and location of any tooth reduction necessary to
establish proper articulation. Edentulous areas arc outlined, and their
restoration planned. Abutment teeth are examined in the light of the
replacements they are to support. If precision attachments are contemplated, the
preparation of the abutment teeth is planned to enhance the results of the case.
The cuspid relationship is carefully examined, and the type of restoration is
projected. This is an important decision that cannot be made until we have
accurate mandibular recordings because the path of (ravel of the lower cuspid
is determined by the Bennett movement of the case.
By considering all the foregoing factors and conditions, it will be possible for
us to plan our treatment and decide which type of restoration will best
accomplish the desired objective. Our first preference would be for restorations
of the onlay type, but these are neither always practical nor possible. We may
have to resort to veneer crowns in some or all areas, in which case a decision
will have to be made as to the type of veneer material to be used. The
preparations will depend upon the material selected. The order in which the
teeth are to be prepared may require some planning. If the patient is wearing a
removable appliance, we should plot our work to enable him to wear it as long

71

as possible, or we should arrange for its replacement to prevent any
embarrassment to the patient. This is especially true if an anterior tooth is
involved. Usually we prefer to prepare the anterior teeth after alt the posterior
restorations are in place, but sometimes this is not possible, and they may have
to be prepared and temporarily covered before anything else Is done. Good
judgment should dictate the course of action in each case.
In planning our treatment, we must consider the edentulous areas. If a
removable appliance is to be made, the impression can be made for a custom
tray even before the preparations are started. In this way, the tray can be
constructed and ready by the time the mouth is fully prepared. Dovetailing
these procedures will expedite the completion of the entire restoration. The
final impression of the edentulous area should be taken after the attachments
are in the abutment castings. This insures a better relationship of the base lo the
abutment castings.
If any teeth are to be removed, this should precede all other treatment to allow
maximum time for healing. It might be advisable to plan the work so that the
preparations are not started until a reasonable time has elapsed for healing. In
this way, we will not have to wait so long after the teeth are prepared before
proceeding with the construction of the case.
In special situations, any extractions could be done at the same time as tooth
preparation, thus avoiding a second injection al a later dale. For instance, if a
first molar is to be removed in a quadrant that is to be prepared, the adjoining
teeth are prepared and the first molar extracted. After bleeding is somewhat
arrested, the temporary can be made, replacing the extracted molar, In this case
the final quadrant impression is not taken until sometime later when the healing
has taken place. The ridge area will later be recorded in the remount procedure,
which usually is several months later. By this time, the ridge area is sufficiently
healed to allow a good pontic relationship.

72

If an anterior tooth is to be removed, the same procedure is advisable: prepare
the adjoining teeth and then extract the tooth to be removed and make an
immediate temporary. The patient will appreciate this sequence of treatment.
Prognosis:
When we have completed our plan of treatment, we should arrive at a
prognosis for the case. This should be explained to the patient. Often teeth are
involved that are quite questionable. There is no sure-fire method of
determining just how certain teeth will respond to treatment. Sometimes,
happily, the results are amazing. Although we should try to save as many teeth
as possible, occasionally in our enthusiasm we may overstep the bounds of
reason. This is all right as long as we are prepared to change our treatment plan
as the case may warrant. It is good practice to plan our restorations so that, if a
questionable tooth does not respond to treatment, we have an alternative
solution.
Sometimes a case has to be completed with a precision attachment in a healthy
tooth next to a questionable one. For instance, if the upper first bicuspid has a
good periodontium, the second bicuspid and second molar are doubtful, and the
first molar is missing, we would construct a fixed bridge from the second molar
to the second bicuspid and place an attachment in the first bicuspid.
The male attachment, which is pan of the fixed bridge, helps to stabilize the
bridge by virtue at its insertion in the first bicuspid. If the bridge abutments are
to be removed at a later date, the attachment is already in place. Usually there
is a similar condition on the other side, and another attachment has been placed
and paralleled to the first one.
This, then, is what we mean by "treatment planning" and why it is so important
to make a careful study of all the factors involved before treatment is begun.

73

PREPARATION OF THE MOUTH FOR REHABILITATION
Having completed the necessary diagnostic procedures, having decided that
complete oral rehabilitation is indicated, and having made our treatment plan,
we must now prepare the mouth for the restoration.
Depending upon our findings, we will remove or have removed any infective
processes such as retained roots, impactions, unimportant devitalized teeth, and
the like. Today, with proper endodontic treatment, the retention of questionable
strategic teeth is possible. However, since these teeth are potential liabilities
from the standpoint of the complete treatment, often it is wise to include in our
restoration plan the possibility of their loss at a subsequent time. In other
words, we should be prepared for such contingencies as fractures, undetected
decay, and recurrent infection. Whenever feasible, we should provide insurance
against fracture by the use of a metal post and/or collar of metal. As with most
general rules, exceptions are sometimes in order; for example, the retention of
an impacted third molar. If its removal would jeopardize a second molar
needed for a bridge abutment or the removal of a devitalized strategic root in a
patient suspected of having a focus of infection. Occasionally, a perfectly good
tooth may have to be sacrificed because of its relation to the other teeth. It is
not wise to compromise the result of the entire effort just to save a single
tooth".
Treatment of the Soft Tissue:
Most of the cases that we are called upon to treat have some periodontal
involvement, it may vary from slight to very severe. The time of treatment will
depend upon the type and severity of the condition. If it is mild, routine therapy
(scaling and curettage) is sufficient. If the condition is severe, however, certain
considerations must be taken into account. Extensive periodontal surgery may

74

be necessary, and this frequently leaves a noncsthetic result. Although the
removal of infected tissue is very definitely part of our treatment, and, in fact,
one of the criteria of a successfully treated case, still the esthetic considerations
are also important.
What we recommend here is a conservative approach; in other words, only the
very necessary minimum periodontal surgery until the case has been
functioning for a while. It is amazing how much tissue improvement can take
place as a result of good dentistry with correct contours and proper function. In
many cases the necessary surgery is minimized remarkably.
There is a possible disadvantage to this approach because we cannot determine
beforehand exactly how much change will take place; it sometimes becomes
necessary to re-prepare several teeth in order to obtain a more esthetic effect.
This may be the price of conservatism. However, after one observes the
improvement of several cases following the establishment of proper function, it
is natural lo conclude that this is the better approach. It becomes a matter of
personal judgment.
Posterior Region:
The location of the severely involved tissue is important. The posterior
segments are more difficult to keep clean and stimulated by home care. From
an esthetic standpoint, they are not so essential as the anterior. Consequently, it
seems more logical to strive to remove all periodontal pockets posteriorly, even
if this entails extensive surgery. The abnormally long crowns required by these
procedures are less conspicuous in the posterior region. The restorations, if
they are full crowns, should be made to cover all exposed tooth structure to
prevent the possibility of secondary decay. Just as the soft posterior tissues are
difficult to care for properly by home care, so is it difficult to keep the tooth
surfaces clean to prevent decay.

75

Anterior Region:
In the anterior region, where esthetics is so important, it may be necessary to
accept a compromise. Shallow pockets, which can easily be kept under control
by home care and frequent visits to the dentist, may be the lesser of two evils.
Our experience indicates that when a mouth is restored to proper function, such
pockets as remain either improve or stay the same. They seldom become worse.
All that is required is proper function, frequent curettage, and good home care.
From an esthetic point of view, this is better than denuded root surfaces or
excessively long crowns, which would require a gingival mask to restore the
esthetics.
Preparation of the Teeth:
The type of preparation to be used in the treatment of the function of an entire
dentition is dependent on several conditions. It is our problem to attach or place
restorations that will function properly. How these restorations arc to be placed
in or on the teeth will depend primarily upon the relationship of the teeth to
each other and to their opposing members. In order to be able to plan this
procedure correctly, we need carefully made study casts, properly mounted on
an adjustable articulator that duplicates the patient's jaw movements. This
presupposes that accurate registrations have already been taken and a proper
mounting of the casts made with a face-bow transfer and a good centric relation
record. If such is the case, we are now in a position to observe the relationship
of the teeth to each other.
It should begin to be apparent that the decision on how the teeth are to be
prepared will rest on a determination of the cuspal relationship necessary to
make the mouth function properly. In other words, we will have to visualize the
finished articulation before we can grind away tooth surfaces. It is usually a
wise procedure to prepare the teeth of the mounted casts and to wax up the case

76

sufficiently well to arrive at an accurate picture of where the cusps are going to
fall.
Once we have a substantial idea of the articulation to be established, we are in a
position to decide how the teeth are to be prepared. Certain areas will have to
be removed to allow space for an opposing cusp. Certain-areas will have to be
built up to make the proper contact. Certain teeth will have to be warped in
order that they may interdigitate properly with the opposing members. The
forces of articulation will have to be visualized, and their dissipation planned.
Method of Treatment:
There are a number of factors that will determine whether a case can be treated
by onlays or whether it must be treated by full coverage.
Adverse relationship of the Long Axis of the teeth: Frequently, when the
properly mounted study casts arc examined, it will become evident that the
long axes of the upper and lower teeth are not ideally related. The long axis of
an upper tooth may be directly over the long axis of the opposing lower tooth.
Such an arrangement precludes the use of onlays in the reconstruction
procedures, for it would not be possible to interdigitate the upper and lower
cusps properly without producing a monstrous result. This situation, of
necessity, requires the use of full coverage.
In some cases where the long axes of the upper and lower posterior teeth arc
not ideal, it may be possible to achieve a suitable articulation by warping onlay
preparations. For example, by overbuilding the mesial of a lower onlay and the
distal of the opposing upper onlay, we may be able to effect a functioning
articulation without too great a display of gold on the mesial proximal surfaces
of the upper teeth. On the other hand, it may be necessary to overbuild the
mesial of the upper posterior teeth while overbuilding the distal of the opposing
lower teeth. This is less desirable from an esthetic stand- point because of the

77

excessive display of metal. It is possible, of course, to overcome this condition
by using full veneer coverage. Still, after observing the change that has taker,
place in some veneers after a number of years, I am inclined to wonder whether
it would not have been better in these cases to have had a display of metal
rather than discolored veneer material. The use of porcelain veneers has
overcome this to some extent.
Insufficient Overjet of the Posterior teeth: In our discussion of articulation, it
was demonstrated that properly articulated occlusal surfaces require an overjet
of the upper posterior teeth. If there is an insufficient buccal overjet, then
onlays are again precluded. A condition such as this would necessitate the
construction of onlays that have a ledge from the gold to the tooth surface, and
this would not be satisfactory. Therefore, to establish proper buccal overjet and
have restorations that blend with the tooth structure, full coverage is here
indicated.
Cross-Bite Relationship: Very seldom can natural teeth in a crossbite
relationship be restored to proper function by means of onlays. Occasionally
this is possible if the teeth happen to be properly tipped and ideally
interdigitated. Usually, however, a cross-bite relationship must be treated by
full coverage. This is not to imply that the teeth can be restored to a normal
relationship by full coverage, for that would require too much tilting of the long
axis. Rather, we mean that full coverage is the only method by which a proper
cross-bite relationship can be established when it is indicated.
Caries-Susceptible Mouth: Mouths that have required many fillings over the
years are usually candidates for full coverage. Where we find M.O.D.
restorations as well as Class V restorations, both buccal and lingual, it hardly
seems wise to labor merely to have a few islands of enamel. Full coverage, of
course, does not rule out the possibility of future decay. As a matter of fact, a
caries- susceptible mouth must be watched very closely after full coverage

78

because the margins of the restorations are, for (he most part, hidden under the
free margin of the gingiva.
Thus far, it might appear that the obvious way to treat all cases is by full
coverage. Although it is true that it is much easier and quicker to prepare a full
crown or a series of full crowns than to prepare satisfactory onlays, it is also
true that considerably more tooth structure has to be sacrificed in a full crown
preparation. Also, it is extremely difficult to properly contour full crowns. To
date, there is no satisfactory substitute for natural tooth structures. From many
standpoints, plastic veneers are far from desirable, and porcelain has its
drawbacks.
Wherever possible, the restoration of choice is the onlay, and for these reasons:
-There is less destruction of tooth structure.. - There are no veneers to construct
or maintain. -There are fewer margins in areas susceptible to decay. -There are
more guides left for proper contouring.
Use of Full Coverage:
In cases where it is not practical to use onlays, a definite compromise is
indicated, and we must resort to full coverage. If the result is to be satisfactory,
we must be guided by certain considerations.
The reduction of the occlusal surface must be executed so as to allow sufficient
depth for the opposing cusp. In other words, it visually is not enough to cut
straight across the occlusal surface; it has to be reduced more mesially and
distally. depending upon the relationship of the tooth to its antagonist. Here is
another advantage of the onlay preparation: in most cases it provides ample
space in its proximal box form.
The reduction of the buccal surface must be made with the requirements of a
veneer in mind, when one is indicated. Sufficient tooth structure must be

79

removed to allow for an adequate thickness of veneer material. Furthermore,
the reduction must be carried below the gingiva when esthetics is a prime
factor.
The most satisfactory type of full coverage preparation is the chamfer. This
conclusion is based on a long and careful observation of both chamfer and full
shoulder preparations. In reconstruction cases, restorations are temporarily
cemented for rather lengthy periods, and it has been found that washouts occur
less frequently under chamfer-type preparations than under full shoulders.
It Is almost impossible to cast accurately to a complete shoulder preparation. It
is also considerably' more difficult to adequately seat a restoration that has a
full shoulder. Moreover, when the full shoulder is used as a fixed bridge
abutment, the problem of perfectly seating the restoration is increased.
Use of Onlays:
Onlays, too, must be intelligently prepared, and the following principles and
procedures observed:
-The cavity outline should permit the restoration (o blend naturally into the
remaining contours of the tooth structure.
-The cavity margins should be carried to immune areas; in other words,
extension for prevention.
-The margins must be carried beyond the occluding surfaces so that function
will not tend '.o open them.
-All functioning surfaces should be covered or "shoed" to minimize the
possibility of a sheared cusp.
-

Flat gingival seats, square walls, and reasonable depth for a sufficient

thickness of filling material are required to insure retention and adequate

80

strength against swaging and opening of the margins. Slice preparations are not
suitable.
- Cavity margins should end in sound tooth structure.
-

As long as sufficient retention is obtained, it is not necessary to carry the

proximal margins below the free margin of the gum.
-

Cavity

outlines

must

include

sufficient

areas

to

permit

articulation to be established without an undue display of filling material.
This is especially important for the cuspids and the anteriors.
-

Proper bevels should be employed to enhance the life of the restorations.

Short, thick bevels are preferable to thin ones.
-

Accessory anchorage in the form of pits or grooves may occasionally be

required for adequate retention.
- A!! ground surfaces should be polished with fine stones, diamonds, or cutile
fish discs.
Pin-Ledge Restorations:
Extremely valuable in full mouth rehabilitation is the pin-ledge type of
preparation. Until recently, it was a rather difficult restoration to construct and
therefore was not often used. Now, however, because of the technique
developed by
Dr. B: David Shooshan (I960) of Pasadena. California, the pin-ledge has again
assumed its rightful place in dentistry. New burs and drills, coupled with pylon
bristles for making the indirect impressions and the wax patterns, have
simplified the construction of this type of restoration.

81

In many instances where the lingual area of an anterior tooth has to be but it up
for contact, it is easy to make a pin-ledge preparation. Often the enamel does
not have to be removed at all. The pinholes are located clear of the pulp and
started with a A -round bur. A 24- or 27-lhousandth twist drill is then used to
make the pinholes. If desired, a slight ledge may be added for gold bulk. The
pinholes must be parallel. This is an easy procedure, provided one docs not
move his finger-rest after starting to drill the holes. The hand and arm must be
kept rigid to maintain the parallelism of the hand niece and bur. If one is not
experienced in this procedure, it is wise to practice on extracted teeth on a
manikin.
Depending upon the particular conditions present, many variations arc possible.
Frequently a Class 111 cavity is encountered on one side of the preparation,
and here we may make an old-fashioned groove and a proximal slice.
If the pin-ledges are to be used as a periodontal splint, then the proximal
contact areas may be slightly prepared with a flame stone or disc to permit
soldering to the adjacent pin-ledge. Pin-ledge preparations are adequate to
carry anterior pontics without destruction of all the abutment tooth
structure(fig-25). A much stronger, more retentive pin-ledge preparation is
taught by Dr. William H. Pruden, 11.
The lingual area is reduced with a football-shaped diamond (Wl). The ledge is
cut lingual to the incisal edge, leaving enough thickness of tooth structure so
that the gold will not cast a shadow. Use a cylindrical diamond for this ledge.
Use the same diamond to make the seats for the pinholes -one mesial, one
distal, and one in the cingulum. Start the holes with a !/2-round bur. Then with
a slow-speed hand- piece and a 699 steel bur, make the pinholes, going from
one to the other, maintaining parallelism with the hand piece. The holes are
made parallel to the- labial surface of the tooth to avoid the pulp. The holes are
trued up with a 700 steel bur. (On lower anteriors stop at 699). With a flame-

82

shaped, smooth cutting diamond; place a finishing bevel around the edge of the
lingual area, and on the incisal edge of the mesio-distal ledge. The impression
is taken in hydrocolloid. using a 25-gauge needle lo deposit the syringe
hydrocolloid in the pinholes. Deposit the syringe material slowly so not lo trap
any air. The heavy-bodied, tempered hydrocolloid in a water-cooled tray is
quickly placed over the syringe material and the impression is cooled for 5
minutes. A stone cast is poured in good die stone. After lubricating the die, the
wax pattern is formed, invested, and cast in a hard gold. The main difference
between this pin-ledge and the previously described technique is the size of the
pinhole. A larger, tapered pin is much stronger and more retentive than the
thinner .027 pins. The length of the pins is approximately 2 to 4 mm., or as
long as is feasible without reaching the pulp.
High Speed:
Methods of preparing the teeth are changing so rapidly today that it is
impossible to cover all of their ramifications. Some generalizations, however,
can be made.
High speed in dentistry is here to stay. Preparations are easier to make, and the
procedure is less fatiguing to the patient. Whereas in the past, tooth preparation
in full mouth rehabilitation was a real task, now, thanks to improved
anesthetics, diamonds, carbides, and high-speed equipment, this phase of the
treatment is the easiest. Many precautions, of course, have to be observed with
the rapidly cutting instrument. Since good vision is obviously necessary, the
lighting facilities should be better than average. Only good carbide burs and
diamond points should be used, and careful control is mandatory. To avoid
possible trauma, the oral tissue must be retracted (preferably by an assistant).
So that there are no "fried pulps." adequate cooling Is essential. The use of air'
and water with an automatic attachment is recommended. Adequate aspiration

83

is also necessary with fluid coolants, and are should be taken to prevent the
propulsion of tooth and restoration material into the patient's throat.
Helpful Hints:
Because they have proved to be of value, the following work habits and
procedures are recommenced:
-Whenever possible, work in a sitting position. Apart from the fact that this is
less tiring to the operator, a more relaxed feeling is transmitted to the patient.
-Prepare the teeth in quadrants. With one injection of anesthetic, it is usually
possible to prepare four teeth as readily as one or two.
-Make the same cuts on all the teeth before discarding the cutting point, thereby
getting the maximum work out of an instrument before changing to another.
-Frequently examine the progress made. Using air to clear the field. -At the
preparation stage, remove only enough decay necessary to prepare the tooth.
Complete removal at this time may sometimes create problems in impression
inking. The only exception is where there would be danger of pulpal
involvement unless complete removals were resorted to. In this case, the decay
should be removed and replaced with cement. This cement, in turn, should
be removed prior to final cementation so that there will be just one mix of
cement between the restoration and the tooth.
- Carefully examine all margins and the tooth structure adjacent to the margins,
especially in the gingival areas. There may be calculus present that must be
removed. Restorations, after all, are to be made against sound tooth structure,
not against a layer of calculus.
-Carefully examine all preparations for under cuts, for definite, smooth finish
lines, and to determine whether the tooth structure has been adequately
removed in the proper places.

84

When the preparations are finally completed to our satisfaction, we can proceed
to make the impressions
Temporary Coverage of Prepared Teeth:
After we have prepared the teeth and made the impressions, it is necessary to
give some temporary protection to the preparations Usually we make our
"temporaries' before making the impressions. Those made of gutta-percha will
help retraction. Those made of acrylic can be trimmed and polished by the
technician while we make the impressions.
On lay Type:
If the preparations are of the onlay type, hard gutta-percha is used to form a
continuous bridge from one preparation to the next (usually there are four in a
row). The gutta-percha bridge is trimmed and adjusted to the opposing teeth
and then cemented in place with a temporary cement, such as MOYCO,
Pulprotex, or Temp Bond to prevent sensitivity. A temporary gutta-percha
filling should never be placed without some type of temporary cement to keep
saliva from seeping between it and the preparation. This type of temporary
coverage is adequate for a week or ten days, during which time a temporary
splint is made of good scrap gold.
Occasionally, an aluminium shell is used for temporary protection of a
preparation. The shell should be carefully fitted and lined with soft guttapercha and then cemented to place with temporary cement.
Full-Coverage Type:
In most cases, where full coverage is indicated, the best temporary coverage
can be quickly made with self-curing plastic. Prior to preparation of the teeth,
but after diagnosis and treatment planning, the study casts are marked
according to the quadrants to be prepared. Any edentulous areas between the

85

teeth are filled in with wax and carved into suitable pontics. A thin layer of wax
is applied with a spatula to the buccal and lingual areas of the remaining teeth
and over the gingival tissues adjacent to the teeth(fig-26). This thin layer of
wax permits us to make a slightly oversized eggshell. The over sizing will
allow for the shrinking of the self-curing plastic; it will provide sufficient
thickness in the eggshell; and it will enable the shell to clear the preparations
when it is seated in the relining procedure that follows. The gingival relief will
prevent impingement of the soft tissues by the eggshell.
After (he study cast has been prepared as described (both sides can be done at
(he same time and the anteriors, too, if involved), an alginate or hydrocolloid
impression is taken of the cast. The impression is separated from the cast, and a
thin layer of self-curing plastic is then applied(fig-27) with a camel's-hair
brush. Small amounts of the powder and liquid should be picked up with the
brush in his application. The liquid causes the powder to spread evenly in the
impression. The impression is lilted to permit the material to flow where we
want it. Since the desired result is to have an eggshell of equal thickness in
every area, we should avoid overbuilding the material in any section. When the
surface of the impression of the teeth is evenly lined, some material should be
allowed to build up the gingival tissue areas, about 2 or 3 mm. beyond the
preparation.
After the plastic has cured, the eggshell can be removed in quadrants and stored
until the preparations are made. The shells should be kept in a proper storage
container so that they will remain moist.
When a quadrant is prepared, and before the impression is made, the eggshell is
tried on the preparations to make sure that it seats perfectly. It is then relined on
the prepared teeth. The teeth and gingival tissues are lubricated with mineral oil
or petroleum jelly (Nu-Life Nu-Lube4). and the eggshell is tilled with a mix of
self-curing plastic. The shell is placed on the preparations, and the patient is

86

instructed to close the teeth slowly. Any gross excess is removed with a plastic
instrument, and the patient is again instructed to close. After a minute or so, the
relined shell is gently lifted to insure its removal, but it is not removed
completely. It is then reseated; the patient is told to close once more; and the
shell is cooled with water to prevent overheating.
When the self-curing plastic has hardened, the eggshell is removed and
trimmed, and the impression procedures are carried out. After the impressions
are obtained, the relined and trimmed shell is ready to be cemented to place
with temporary cement(fig-28). It seldom requires any occlusal adjustment;
when it does, this can be accomplished very easily with a rubber wheel.
Another method of making a more durable temporary plastic splint has been
developed by Dr. Morton Amsterdam (1959) of Philadelphia, who uses soft
gold shells for marginal adaptation.
There are several other ways to make good plastic temporaries. Instead of an
alginate impression in which an eggshell is made, a wax impression can be
taken either from the mouth or the study model. If an edentulous area is
present, the area can be scooped out of the wax impression with a heated
vulcanite scraper or similar wax instrument. This area will need some
reshaping after the temporary is made, but if time is of the essence, it may be
worthwhile. The prepared wax impression is filled with self-curing acrylic
resin and seated over the lubricated teeth. Removal before polymerization will
insure against locking it to place. If your timing is just right, you can peel the
acrylic out of the wax impression and. while it is in a plastic state, trim it with a
pair of scissors. Replace the stiil-pliable temporary on the teeth and have the
patient bite down. This will reduce the amount of occlusal adjustment needed.
Probably the easiest and best temporary can be made by means of the Omnivac
technique. The study cast is prepared as necessary. Missing teeth are waxed in

87

place; any desirable occlusal corrections may be made. Then an alginate
impression is taken of the entire cast. A cast is poured up in stone and the new
cast is removed from the impression. A hole is made through the center of the
cast with a large vulcanite bur. The cast is placed on the Omnivac stand, a sheet
of .020 Temp Splint material made by Omnivac is placed in the frame, and the
heating element is turned on. When the sheet is sufficiently heated it will sag in
the middle about an inch. At this point, the frame is dropped onto the model at
the same time that the vacuum is turned on. The heated sheet will be adapted to
the cast. When it is cool enough, remove it from Ihe frame and trim it to just
beyond the gingival margins. On the upper, the vault area is cut out to remove
the projection into the suction hole. On the lower, the lingual is trimmed to just
beyond the gingival margins(fig-29).
When one quadrant is prepared, lubricate the inside of the shell and the
prepared teeth. Fill the shell on the prepared side with self-curing plastic (a
very good one is Coidpac). Seat the full splint with the plastic on the side of the
prepared teeth and have the patient close firmly against it. The full splint will
help to equalize the bite relationship so that there will be a minimum of
occlusal adjustment necessary Again, if you watch it carefully, you can
remove, the spiint before it sets. Peel it out of the Omnivac shell and roughly
trim the excess with a pair of scissors. While it is still pliable, replace it on the
preparations and have the patient close firmly.. Repeatedly lift it and reseat it to
avoid locking in place. When it is set. remove it and trim and polish it. It may
desirable to refit the splint in the gingival areas. Apply a little petroleum jelly
to the sulcus. Blow the excess out with a gentle blast of air. Then, with a
camel's-hair brush, apply some powder and liquid in sulcus. Moisten the
trimmed splint with some of the monomer and seat it so that the gingival
application will unite with the set shell. A gingivatly well-adapted shell can
thus be produced. Complete the polishing and temporarily cement it to place.

88

PANKEY-MANN SCHUYLER PHILOSOPHY OF COMPLETE
REHABILITATION
One of the most practical philosophies for occlusal rehabilitation is the
rationale or treatment that was originally organized into a workable concept by
Dr. L.D. Pankey. Utilizing the "Principles of occlusion" espoused by Dr. Clyde
Schuyler. Dr. Pankey integrated different aspects of several treatment
approaches into an orderly plan for achieving an optimum occlusal result \\\&i
minimum stress on the patient or the dentist,
Dr Arvin Mann Contributed to the concept b> working with Dr. Pankey in the
development of the first specialUed instrument for de veloping the occlusal
plane. The instrument became known as the Pankey-Mann instrument, and
even though it has long ago been replaced by a simpler system the over all
concept of treatment is still referred to as the Pankey-Mann-Schuyler
Philosophy (abbreviated to P.M.S)
Contrary to some popular misconceptions, the P.M.S. approach is not so much
a technique as it is a philosophy of treatment that organizes the reconstruction
of an occlusion into a sequence of goals that must be fulfilled. It is true that
certain techniques have become closely associated with the P.M.S, philosophy,
but it is also true that there has been a continuous trend toward improving and
simplifying almost every aspect of treatment without noticeably changing the
basic philosophy of treatment. Furthermore, the overall concept of treatment is
not limited to any specific instrument or method. There is consideration
flexibility of treatment within the PMS. philosophy as long as its goals of
optimum occlusions are not sacrificed.
Since its inception, the philosophy has had as its goal the fulfillment of the
following principles of occlusion as advocated by Schuyler:

89

1. A static coordinated occlusal contact of the maximum number of teeth when
the mandible is in centric relation.
2. An anterior guidance that is in harmony with function in lateral eccentric
position on the working side.
3.

Disclusion by the anterior guidance of all posterior teeth in nrotrusion.

4.

Disclusion of all nonworking inclines in lateral excursions

5.

Group function of the working side inclines in lateral excursions.

Many P.MS, advocates now vary the fifth goal of working side group function
to permit more flexibility in distributing lateral stress.
In order to accomplish these goals, the following sequence is advocated by the
P.M.S. philosophy:
PART I. Examination, diagnosis, treatment planning, prognosis PART 2.
Harmonization of the anterior guidance for best possible esthetics, function,
and comfort
PART 3. Selection of an acceptable occlusal plane and restoration of the lower
posterior occlusion in harmony with the anterior guidance in a manner that will
not interfere with condylar guidance.
PART 4. Restoration of the upper posterior occlusion in harmony with the
anterior guidance and condylar guidance. The functionally generated path
technique is so closely allied with this part of the reconstruction that it may
almost be considered part of the concept.
Bach one of these steps has undergone continuous metamorphosis as
techniques to accomplish the goal have been improved and modified with a
wide choice of sophisticated options. One of the most impressive advantages of

90

P.M.S. is the latitude of sophistication it permits. Treatment modes within the
concept can be varied from the simplest techniques for the beginning
restorative dentist to the most precise details of the master reconstructionist.
The determination of an acceptable occlusal plane was first simplified by
Fillstrc and then further improved by Broaiirick. The Broadrick occlusal Plane
Analyzer is so simple to use that it has become the standard method of
analyzing ccclusai plane for posterior occlusal reconstruction.
The PMS philosophy is not limited to any specific instrument. Swanson and
Wipf adapted the Broadrick "flag" for their temporomandibular joint
stereographic articulator. and Fillastre developed a device for the same
instrument that determines ridge and groove directions on the lower occlusal
wax patterns. The advantages of the technique are many. Some of the major
ones are as follows;
1.

It is possible to diagnose and plan treatment for the entire rehabilitation

before preparing a single tooth.
2.

It is a weII-organized, logical procedure that progresses smoothly with less

wear and (car on the patient, operator, and technician.
3.

There is never a need for preparing or rebuilding more than eight leeth at a

time.
4.

It divides the rehabilitation into separate series of appointments. It is

neither necessary nor desirable to do the entire case at one time.
5.

There is no danger of "getting at sea" and losing the patient's present

vertical dimension. The operator knows exactly where he is at all times.

91

6.

The functionally generated path and centric relation are taken on the

occlusal surface of the teeth io be rebuilt at the exact vertical dimension to
which the case will be constructed.
7.

All posterior occlusal contours are programmed by and are in harmony

with both condylar border movements and a perfected anterior guidance.
8.

There is no need for time-consuming techniques and complicated

equipment.
9.

Laboratory procedures are simple and controlled to an extremely fine-

degree by the dentist.
The Pankey-/Mann-Schuyier philosophy of occlusal rehabilitation can fulfill
the most exacting and sophisticated demands // the operator understands the
goals of optimum occlusion. And it can achieve these goals with great
simplicity and orderliness of technique, ll can be combined with other
techniques and it can be adapted to any occlusal problem. An understanding of
the P.M.S. philosophy is a tremendously valuable aspect of the complete dental
education.

92

SELECTING INSTRUMENTS FOR OCCLUSAL REHABILITATION
There are four basic type of instruments that can be used with equal success to
achieve fine results in restorative procedures. The purpose of all good
instrumentation is simply to capture accurately the border pathways of the
teeth, This may be done by reproducing the border movements of the condyles
and then combining the reproduced condylar pathways with corrected anterior
guidance paths. Or it may be done by recording the results of anterior and
posterior determinant pathways at the site of the teeth themselves.
In using any instrument, it must be remembered that anterior guidance is a
product of functional border movements that fall within the outer limits of the
envelope of motion. Recording only condylar pathways does not furnish
enough information for the instrument to precisely reproduce tooth movements
that are in harmony with the envelope of function. The anterior guidance is a
separate entity that must be recorded and programmed into any articulator in
addition to condylar pathways if the instrument is to be used as a device for
reproducing jaw movements.
Anterior guidance is not determined by condylar guidance, so there is no
instrument that is capable of determining how the front end of the mandible
should move. If anterior guidance is correctly determined in the mouth and its
pathways are recorded at the "front end" of the articulator, any one of several
instruments can be used with excellent results.
The simper the articulating device, the more compensation must be made for its
shortcomings. But if compensations can be made easily and accurately, there is
practical value in keeping the instrumentation as simple as possible.

93

Semi adjustable instruments (fig-30):
The biggest shortcoming of semi-adjustable articulators is that condylar
pathways are limited to straight line. Because of this limitation, these
instruments are referred to as check bite articulators. This means that the
horizontal condyle paths are set to align with a bite record made at centric
relation and another bite record made in the protrusive position. The resultant
path is a straight line between the two points. Lateral pathways are set from the
centric bite record plus bite records made in the left lateral and right later jaw
positions. The resultant straight-line gradual side shift of the balancing condyle
determines the amount of immediate side shift for the working side condyle.
If pathways in the skull curve between the two check bite positions, the curve
will not be duplicated on the articulator. Only the two points of the check bite
position will be correct. The path between the two points will be in error.
To minimize the errors of the check bite technique, protrusive and lateral bite
records should be made fairly close to centric relation. The most important part
of the condylar pathway is right after the condyle leaves centric relation, so
taking the eccentric bile record within about 5 mm from centric relation gives
greater accuracy where it is needed most(fig-3 I).
Semi adjustable instrument cannot record the full range of lateral and
protrusive condylar movements, but the mechanical equivalent of tooth
movements can be recorded with as much accuracy as is possible on any
available instrument if the instrument's shortcomings are compensated for with
the following.
1. Customized anterior guidance procedure
2.

Simplified fossae contours technique to relate lower fossae form to the

anterior guidance.

94

3.

Functionally generated path procedures to capture the precise border

movements of the posterior teeth at the correct vertical dimension.
When recorded in this manner the pathways of the posterior teeth reflect the
precise influence of all condylar border movements as well as the anterior
guidance. No interpolation of condylar movement is required because the
border movements are recorded directly at the site where the path of
movements is important at the posterior teeth themselves. The articulator is
thus not used as a duplicator of jaw movements but rather as a device that
relates the functional pathways to the prepared teeth. Since each of the above
refinements can be used with advantage in any instrument approach, they do
not constitute unnecessary added work.
Semi adjustable instruments do not precisely record the Bennet shift, but the
necessary compensations can be easily made. However, even if the instrument
is used with check bite records to set condylar pathways without functionally
generated path procedures, the occlusa! adjustment should still be minimal. It
is possible to record centric relation perfectly, and since it is an easy matter to
disclude all posterior contacts in protrusive and non-working side excursions,
adjustments to these excursions should be minimal.
There are a number of other semi adjustable articulators that can be used with
the same effectiveness as the University Model Hanau. The Whip Mix
Articulator is a popular instrument that has three variations that can be used for
intercondylar distance.
The Hanau Model H. or the Dentatus and Girrbach articulators are among the
most popular nonarcon instruments.

95

Fully adjustable articulators:
The term "fully adjustable" refers to the reproducibility of the patient's
condylar paths. In evaluating any articulator, it should first be noted that no
matter how complex the instrument may be, it can still do no more than the
following:
1.

Reproduce the terminal horizontal axis of condylar rotation.

2.

Reproduce the vertical axis of condylar rotation.

3.

Reproduce the saggittal axis of condylar rotation

4. Permit simultaneous multiple axes of rotation during condylar translations.
5.

Reproduce straight protrusive pathways of each condyle.

6.

Reproduce the pathways of each condyle during straight lateral excursion

of the mandible.
7.

Reproduce the multiple pathways of each condyle during all possible

excursions of the mandible between straight lateral and straight protrusion.
All though there are many claims made regarding complete adjustability, very
few instruments are actually capable of reproducing ail seven of the above
condylar movements without some degree of interpolation.
The first six listed movements cab be accurately reproduced by most quality
gnathologic instruments, but the seventh requirement, the multiple protrusivelateral pathways, must be interpolated from straight lateral and straight
protrusive paths.
There are two basic methods for recording the condylar paths: pantographic
tracings and stereographies. Actually, neither method records the true anatomic

96

contours of the temporomandibular joint, nor does the articulator reproduce the
anatomy of the joint. H is merely a mechanical equivalent that makes the back
end of the articulator capable of going through the same movements that the
back end of the mandible follows in function.
Pantographic instruments:
The use of pantographics has become far more practical since the introduction
of the Denar Pantograph. Because of a simplified procedure of using vinyl
clutch formers, a central bearing point set of clutches can be fabricated in a
matter of a few minutes. The clutches are then adapted to the Denar
Pantograph, which traces mandibular movements on tracing plates.
The pantographic technique does have the advantage that goes with the use of a
central bearing point. With a properly located central bearing point, all occlusal
interferences are disengaged when the condylar pathways are recorded. There
is no tooth contact during the tracing procedures. Manipulation of the mandible
is simpler because of the complete absence of any occlusal interferences at the
opened vertical.
If pantographic tracings are to be used to program the articulator. it is necessary
for the pantograph to be correct. Unfortunately, the pantograph can be no better
than the operator's ability to manipulate the mandible with the pantograph
attached. Allowing the patient to record border movements without expert
assistance from the operator will result in incorrect tracings. They will
generally fall short of the outer border limits. The mandible must be
manipulated to correctly capture the outer limits of movement.
Manipulation should start with the recording of the terminal hinge position and
ail lateral tracings should emanate from it, Failure to do so will result in
restorations with interferences in the extreme border positions just lateral to
centric relation.

97

When manipulating the mandible or a correct pantographic tracing, it is
extremely important that the condyles be in their most superior position for the
centric relation part of the tracing. The central bearing point permits easy
positioning of the condyles into this superior position, but it also permits a very
common error to occur if correct manipulation is not used.
It is very difficult to record correct centric and border movements with patient
sitting up straight. The supine position makes manipulation much simpler.
If a one-handed technique is used lo position the mandible in centric relation
with the central bearing point in place, the dentist must be certain to exert a
downward force on the chin, as the mandible is retruded. This has the effect of
seating the condyle upwards.
The popular Stuart Articulator is another instrument that will also adjust to
paniographic tracings. The selection of which instrument to use is purely a
matter of personal preference.
Disadvantage of pantographic devices is that the tracings must be made at a
considerably opened vertical dimension to make room for the clutches. It is
essential that the terminal hinge axis must be recorded precisely or the incorrect
axis of closure will introduce errors.
It is also probable that in some mouths, at least, the border movements are
different at the opened position from what they are at the correct vertical.
Stercographic instruments (fig-32):
One of the simplest "fully adjustable" instruments to use is the TMJ
Articulator. All border movements can be accurately recorded in three
dimensions by means of simple intraoral clutches that are stabilized by a
central bearing point.

98

The recordings are made by indenting three or flour points into doughy selfcuring acrylic on the surface of the opposite clutch and then moving the
mandible through all border movements. Protrusive lateral movements can be
included. When the stereographic recording is completed, the acrylic guide
paths are allowed to set hard. The condyle paths on the instrument are then
made in self-curing acrylic as dictated by the points of one clutch sliding in the
indented recordings of the other. Since the three dimensional recordings were
made in the mouth by the paths of the condyles. the procedure can be reversed
and the paths in the clutch can dictate the mechanical equivalent of condyle
movement on the articulator(fig-33).
Stereographic techniques have a decided advantage in the use of the three
dimensional recordings. All border pathways can be programmed into the
condylar guidance, including protrusive-lateral movements. The instrument can
be used in combination with customized anterior guidance procedures. It lends
itself well to sophisticated Panl.l;y-Mann-Sen uyler procedures.
The TMJ instrument is an excellent articulator for fabricating dentures. The
intraoral clutches are stabilized by the centra! bearing point and all recordings
are made intraorally within the central area of the bases. This is a decided
advantage over pantographic devices that frequently have a tendency to tilt the
denture base with the weight of the external appendages.
Nonarticulator instruments:
All border movements of the teeth can be accurately recorded and duplicated
without even using an articulator. It is not necessary to reproduce condUe
pathways as long as the effect of the condyle movements can be recorded at the
site of the teeth. An instrument that accomplishes this is called the Gnathic
Relator. It is accurate and adaptable to all the techniques. It is used to best

99

advantage in combination with some type of semi adjustable articulator. but the
articulator itself is not used for reproducing border movements.
It is essential that the anterior guidance by perfected prior to use of the Gnathic
Relator for fabrication of posterior occlusai restorations. A stereographic
device is then set up on centrically related models after the posterior teeth have
been prepared. The relator is then transferred to the mouth for the recording.
No central bearing point is needed because the anterior teeth contact during the
recording.
Because the siereographic recording is made at the correct vertical dimension
with both anterior guidance and condylar guidance influencing the border
movements, no interpolation is required. The recording device itself is
rcpositioned on the master die models, where it becomes the guide for all
movements of the models in relation to each other (fig-34).
The models with the Gnathic Relator attached can be handheld in perfect
centric relation and can be moved through any border pathways by hand. Wax
up and completion of the restorations can be perfected on the handheld models.
"Simple" articulators:
The most important single purpose of an articulator is to relate the upper and
lower models to the correct horizontal axis. Simple hinge articulators do not
permit a correct relationship to the axis of closure. Sizable errors are introduced
into all aspects of occlusai form when correct horizontal and vertical axes are
not used. The problem with simple hinge type articulators is that the only
movements they can make are movements the patient cannot make.
A facebovv mounting is essential for the proper utilization of any articulator.
Articulators that do not accept a facebow mounting have virtually no value for
restorative procedure or occlusal analysis.

100

Without correct mounting procedures, even a perfectly made centric bite record
has limited value. Many dentists who are genuinely striving for preciseness
waste a great amount of time meticulously carrying out procedures that are not
needed.
The use of an infraorbital pointer, as an example, is an extra step that many
dentists use unnecessarily. It has limited practical value because a simple
laboratory procedure can fulfill all the functions of the pointer with far more
accuracy and repeatability. The tattooing of condyle axes is a similar waste of
time.
A facebow recording is one of the essential steps for proper mounting of casts.
After location of the condylar axis in the skull, it provides a method of
transferring that axis to the articulator by relating it lo the upper cast. If a
centric bite record is made at an opened vertical dimension, the accuracy of the
bite record will only be maintained if the closing axis is the same on the
articulator as it was on the patient.
Any change of axis changes the direction of the closing path. Built-in error
results when models are mounted on instruments that do not reproduce the axis
correctly. Instruments that arc capable of reproducing the axis will only do so if
the models are mounted with a facebow. It is good practice to record centric
relation as close to the correct vertical dimension as possible.
The most accurate method for recording the correct horizontal axis include the
use of some type of kinematic device for locating the terminal hinge axis. A
hinge axis can be recorded at any point along the protrusive pathway. Unless
good manipulative technique is used to position the condyles in their terminally
braced position, the recorded hinge axis will be incorrect. Furthermore, even
the most precisely recorded hinge axis cannot compensate fur a missed centric
bite record.

101

A kinematic facebow recording is almost a necessity if the centric bite record is
made at an extreme opened vertical. Bite records made with clutches in place
often fall into this category. However, if the centric bile record can be made at
or near the correct vertical dimension, clinically acceptable accuracy can be
achieved by palpating to locate the axis.
Method of palpation for locating the condylar axis:
From a position behind the patients the operator should place the index finger
over the joint area and ask the patient to open wide. As the condyle translates
forward, the fingertip will drop into the depression iefl by the protruded
condyle. The patient should then close. As the condyle is pulled back into
centric relation, its position can be located by the fingertip. By asking the
patient to repeat an opening-closing arc, it will be possible in most patients to
feel the condylar rotation and to locate the axis within acceptable limits of
accuracy. Once the general center of the condyle is located, accuracy is assured
to within 2 or 3mm. This is acceptable on any mounting that is to be articulated
reasonably close to the correct vertical dimension. The located axis should be
marked on the skin.
It is not always possible to articulate the original diagnostic models of
unequilibrated occlusions near the correct vertical dimension. The centric bite
record must be made before the first tooth contacts
Using the facebow:
The facebow is simply a device that relates the upper cast to the same axis on
the articulator that is present in the skull. A facebow recording is simple to
perform and requires only a minute or two of chair time,
1.

Softened wax is wrapped around the bite fork and positioned against the

upper teeth,

indentations into the wax should be sufficient to stabilize the

102

upper model. The wax should not be penetrated to the metal.

For upper

edentulous ridges, a stable base plate should be constructed and the bite fork
should be attached to a bite rim on the base.
The lower teeth can usually be closed into the underside of the wax to stabilize
the bite fork. If stability cannot be achieved this way. the bite fork should be
held firmly against the upper teeth by the chair side assistant.
It is not necessary to close into centric relation on the bile fork. Its purpose is
for orientation of the upper cast only.
2.While the wax on the bite fork is being chilled by the assistant, the facebow
is positioned and the intercondylar width is recorded. The facebow is set
according to the patient's facial width.
3. The bite fork is reinserted and the facebow is positioned by the dentist so
that the axis locators are positioned in line with the marks on the skin.
4.

While the dentist holds the axis locators in position, the assistant,

without contacting the facebow at any other point, tightens the set screw
mechanism that locks the bite fork into the correct relationship with the
facebow(fig-35).
5.

The axis locators are loosened and their relationship to the marks on the

skin checked. Both locators should be at the same setting and should lightly
contact the skin directly over the marks.

If the position is incorrect, the

locking device should be loosened on the bite fork and the procedure repeated.
If the relationship is correct, the recording is removed from the mouth.
Mounting with the facebow:
The width of the palient's head is recorded on the facebow, but the intercondylar distances will be less, because the condyles are inside the skin and fat

103

layers. Measuring to the outside of the condyle post on the articulator will
compensate for soft tissue thickness and will result in a more accurate
intercondylar distance. This dimension is set on the articulator so that both
condyle posts are at the same setting.
After the intercondylar distance has been set, the axis locator bars are released
and reset to the axle on the articulator. When the facebow is positioned on the
articulator's axle, the upper model is placed in the indentations in the bite
fork(fig-36). The support screw in the front of the facebow is lowered to
support the cast. While an infraorbita! pointer is often used to determine the
vertical position of the cast, it is an unnecessary procedure. If the labial surface
of the upper incisors is aligned with the perpendicular, the cast position will be
in a good relationship.
A common mistake in positioning the upper model is to align the incisal edges
with the groove on the incisal guide pin. This usually results in positioning the
model too high on the articulator. Negative horizontal condylar paths are often
a side result of such cast positioning. The mark on the guide pin should be
ignored.
When the cast height has been determined, it should be supported during the
mounting procedure.
When the upper mode! is joined to the mounting ring on the articulator, the
facebow can be removed. The lower model is then articulated to the upper with
a centric relation bile record. If the incisal guide pin is lengthened an amount
equal to the thickness of ihc bite record, the upper bow of the articulator will be
horizontal when the bite record is removed and the models are in contact.

104

Setting the horizontal condylar guidance:
After the models are mounted in centric relation, a second bite record made
with the mandible protruded approximately 5mm. can be used to set the
horizontal condyle paths. As check bite techniques do have limitations, but in
most cases the procedure can be used with reasonable practicality if the
protrusive bite record is not made too far forward of centric relation.
When using a protrusive check bite, it should be trimmed back to the tips of
each upper and lower cusp so that the stone model is clearly visible where it
contacts the wax bite. The centric locks are released at the condyle path and the
upper model is moved back into the indentations in the protrusive bite. The
condyle path is now altered Lo varying degrees of steepness until the model fits
precisely into the bite record with no separation between the stone and the bite.
If there is a separation at the distal part of the bite, the guidance is too steep. An
anterior separation between model and bite record results form the condylar
guidance being set too flat.
Setting the lateral condylar guidance:
Check bites made in each lateral excursion can be used to set the lateral
condylar paths. The centric lock is released and the lateral adjustment lock
screw is loosened on each side. The lateral pins are opened to the widest
positions. The left lateral check bite i? place and the models are positioned into
the bite record indentations. The balancing side condyle path on the right side
of the articulator is rotated in until it contacts the lateral centric stop on the
axle. This repeated for the opposite side. The protrusive check bite should be
rechecked after setting the lateral guidances.

105

Using transfer bite records to eliminate the infraorbital pointer procedure:
The infraorbital pointer provides a uniform method of establishing the vertical
position of the upper cast on the articulator. Once the condylar pathways are set
(either by check bite, pantograph, or stereograph), there will be .',o need to
reset them if the original upper model and all subsequent models are all at the
same position.

As a restorative case progresses, teeth are equilibrated,

prepared, and restored. New models are required at each step of the restorative
procedure. The usual procedure is to mount each new set of models with a new
facebow recording that also employs an infraorbital pointer repeatedly set to
the same spot on the patient's face. Condyle axis location is often tattooed on
the skin to assure accuracy of that part of the facebow recording. While the
procedure is effective, it requires an unnecessary waste of time. The same
results can be aeh ieved v. ith a simple laboratory step.
As already discussed, the vertical position of the upper cast can be set by
raising or lowering the front of the facebow until the labial surfaces of the
central incisors are vertical. Some anterior teeth are tilted inward and some are
near horizontal. If the centra! teeth are not in a normal relationship, the occlusal
plane can be used as a guide for positioning the upper cast. The front of the
occlusal plane should be set slightly lower than the back. This may seem
arbitrary, but regardless of the position of the casts vertically they will not lose
their correct relationship with the terminal axis as long as the model is
positioned on the bite fork and the axis locators are in position on the
articulator. Condylar guidances are not set until the casts are mounted and then
these guidances are relative to whatever vertical cast position is used.
When changes are made in the mouth and new models are poured, they can be
mounted in precisely the same relationship as the previous casts by using a
transfer bite. Let us use an example to explain the procedure. The original
diagnostic models have been made. Equilibration procedures arc then

106

completed that change the occlusal surfaces and new impressions are made.
The new models can be mounted in the same relationship to the condyles
without taking a new facebow. A simple wax bite is made on the original
models in centric relation on the articulator. When the wax is in place, the bite
is opened so the incisal guide in pin is dropped to contact the guide table. The
upper cast is then removed and the new cast is positioned into the bile record.
The original lower model is still in place and the guide pin is still lengthened at
the same position.
The new upper model will have voids against the transfer bite record, but there
will still be ample numbers of untouched stops so that the new model will be
completely stable in the bite record in spite of the voids. It should be joined in
that position to the upper mounting ring.

After the new upper model is

mounted, the guide a restorative case progresses, teeth are equilibrated,
prepared, and restored. New models are required at each step of the restorative
procedure. The usual procedure is to mount each new set of models with a new
facebow recording that also employs an infraorbital pointer repeatedly set to
the same spot on the patient's face. Condyle axis location is often tattooed on
the skin to assure accuracy of that part of the facebow recording. While the
procedure is effective, it requires an unnecessary waste of time. The same
results can be achieved with a simple laboratory step.
As already discussed, the vertical position of the upper cast can be set by
raising or lowering the front of the facebow until the labial surfaces of the
central incisors are vertical. Some anterior teeth are tilted inward and some are
near horizontal. If the central teeth are not in a normal relationship, the occlusal
plane can be used as a guide for positioning the upper cast. The front of the
occlusal plane should be set slightly lower than the back. This may seem
arbitrary, but regardless of the position of the casts vertically, they will not lose
their correct relationship with the terminal axis as long as the model is

107

positioned on the bite fork and the axis locators are in position on the
articulator. Condylar guidances are not set until the casts are mounted and then
these guidances are relative to whatever vertical cast position is used.
When changes are made in the mouth and new models are poured, they can be
mounted in precisely the same relationship as the previous casts by using a
transfer bite. Let us use an example to explain the procedure. The original
diagnostic models have been made. Equilibration procedures are then
completed that change the occlusal surfaces and new impressions are made.
The new models can be mounted in the same relationship to the condyles
without taking a new facebow. A simple wax bite is made on the original
models in centric relation on the articulator. When the wax is in place, the bite
is opened so the incisal guide in pin is dropped to contact the guide table. The
upper cast is then removed and the new cast is positioned into the bite record.
The original lower model is still in place and the guide pin is still lengthened at
the same position.
The new upper model will have voids against the transfer bite record, but there
will still be ample numbers of untouched stops so that the new model wilt be
completely stable in the bite record in spite of the voids. It should be joined in
that position to the upper mounting ring. After the new upper model is
mounted, the guide pin is reset back lo its regular position. The new lower
model is then mounted by means of a new centric relation bite record made on
the patient.
This procedure can be repeated at each new step of the restorative treatment.
As an example, when the lower posterior teeth are prepared, that model is
articulated against the correctly mounted upper cast. After the lower
restorations are completed, a transfer bite record is made on the articulator with
the restorations in place. The guide pin is dropped to contact the guide table
when the bite record is in position. After placement of the restorations, a lower

108

impression is made and new model is positioned into the transfer bite record
and joined to the lower mounting ring. The guide pin is then reset and the new
upper cast (which may be a die model of prepared upper teeth) is articulated
against the lower model with a new centric relation bite record.
This procedure is simple, yet very accurate, ll eliminates the chair time required
for taking repeated facebow records and simplifies the laboratory remounting
procedures. It works as well on gnathologic instrumentation as it does on semi
adjustable articulators.

109

ANTERIOR GUIDANCE
Perhaps the most sophisticated test of a restorative dentist's skill is how happy
his palients are when the anterior teeth have been restored. The correct
relationship of the upper and lower anterior teeth is so critical that differences
of a millimeter or less in incisal edge posilion can feel grotesque to a patient.
Radical changes in lip support, incisal edge position, and lingua! contours may
change more than a patient's natural appearance. Along with the discomfort and
the look of artificiality, improperly restored anterior teeth may contribute to the
destruction of the entire dentition.
One thing that every dentist should know before he attempts to restore anterior
teeth is that besides being nice to look at and to bite sandwiches with, the
anterior teeth have the very important job of protecting the back teeth. So
important is this job of the anterior guiding inclines that posterior teeth that are
not protected from lateral or protrusive stresses by the anterior teeth will, in
time, almost certainly be stressed beyond the resistance of their supporting
structures.
In spite of how good the upper front teeth may look their chance of staying
healthy and keeping the back teeth healthy depends on their lingual contours,
specifically the contact of the lower anterior teeth against the upper anterior
teeth in centric, "long centri'c", straight protrusive, and lateral excursions. This
dynamic relationship of the lower anterior teeth against the upper anterior teeth
through all ranges of function is called the anterior guidance. As such, it
literally sets the limits of movement of the front end of the mandible.
We will imagine that all the back teeth have been shortened through
preparation so that they cannot touch in any position of the mandible. Now
without any possibility of posterior tooth interference, we visualize the
mandibie closing in a terminal axis closure until the front teeth contact

110

simultaneously against stable centric stops at the correct vertical dimension, the
First requirement of good anterior relationship has been fulfilled. The mandible
should be closed into a stable tripod and the terminally braced condyies serving
as the other two legs(fig-37).
Since this mandible tripod is a lever that hinges at the condyies. it will be
apparent that the power for cosing this lever is in muscles that exert the closing
force between the condyies and the front teeth.

The anterior teeth are ail

forward of the closing muscle power, so to exert stress on the anterior teeth.
The mechanical result of the closing muscles would be like trying to crack a
walnut by placing it at the tips of the handles of a nutcracker and squeezing the
handles up by the hinge. This is the unique position of resistance to stress that
the anterior teeth enjoy by virtue of their relationship to the condylar fulcrum
and the source of muscle power(fig-38).
The condyles. braced firmly against bone and dense ligaments, form a very
strong hinge that is completely capable of resisting the power of the closing
muscles. The anterior teeth, when their position allows it. should be made to
form a very stable stop for the front of the mandible and thereby limit its
closing motion. If the closing motion of the mandible is stopped by the incisal
edges of all six lower anterior teeth against stable holding contacts of the six
upper anteriors, we have not only taken advantage of the position of the front
teeth, we have also strengthened that position by distributing the stresses.
It is a popular fallacy, however, that whatever path the condyles follow must be
duplicated in the lingual surfaces of the upper anterior teeth so that the lower
anterior teeth can follow the same path. This is wrong. Condylar paths do not
dictate anterior guidance, and there is no need or even advantage to try to make
the anterior guidance duplicate condylar guidance. Advocates of such a concept
have failed to recognize that the condyles can rotate as they move along their

111

protrusive pathways. This allows the front end of the mandible to follow a
completely different path without interfering with condylar path.
The path that the condyles travel dictates the cuter limits to which the mandible
can move. These outer limitations are referred to as the envelope of motion.
The path that the front end of the mandible follows is dictated by functional
movements of muscle as it relates the lower anterior teeth to the upper anterior
teeth in the chewing cycle. The outer limits of these functional movements are
referred to as the envelope of function, Such functional movements occur
within the limits of condylar border movements and consequently should be
treated as separate entity.
To better understand how the anterior guidance differs from the condylar
guidance, we return to our visualization of the upside-down tripod. Since the
condyles on the back two legs of the tripod are rounded (so that the mandible
can rotate around them), it is easy to see how the lower incisors that form the
front leg of the tripod can slide forward on a variety of paths without conflict to
either the front path or the condyle path. The same condylar path that permits
the lower anterior teeth to follow a horizontal path forward will just as easily
permit them to follow a 10-degree. a 30-dcgree, or even a steeper path. It does
not matter whether the anterior path is flat or curved, concave, convex or
parabolic, the rotating condyles sliding down the unchanged condylar path
permit the lower anterior teeth to follow any number of path variations without
interference.
If the nature of the condyle path does not dictate the anterior guidance, it
should be clear that the recording of condylar pathways does not in itself
furnish enough information to optimally restore anterior teeth. The dentist who
prepares all the teeth in either arch (or worse yet. in both arches) sometimes
believes he has all the information needed if he mounts his models on a
completely adjustable instrument. When he has properly recorded and

112

transferred all the condylar pathways to a fine instrument, he may think that he
"has the patient's head on his laboratory bench". Such is not the case. The best
that any technician can do with such information is to guess at the contours of
the anterior teeth. We do not wish to belittle the importance of condylar
guidance. It is extremely important, and capturing the effect of condylar
pathways by some method is one bit of information that is essential to the
completion of theocclusal contours, but is only of the needed information.
Condylar pathways do not dictate the correct smile line. The precise incisal
edge position varies greatly as the length of the lip and the degree of flaccidity
or tightness of the lip varies. People with tight lips usually have anterior teeth
that are positioned more vertically than those of people with flaccid lips, and
even if the condylar guidance were the same in both types of patients, the
anterior guidance would be different. It would almost always be steeper in the
tight-lipped individual.
It is both practical and logical to work out the details of anterior contours in ihe
mouth. When done in an orderly sequence, we can determine precisely how
much "long centric" is needed, we can test variations in incisal edge position
for phonetic correctness, and we can be guided by the mobility patterns of teeth
as they are subjected to varying degrees of lateral stress. The greater the
hypermobility, the greater the need for minimizing lateral stresses. The less the
mobility, the less need for changing even steep anterior inclines. By making
any changes directly in the mouth, the patient is given the opportunity of
approving the appearance and trying out the function comfort and phonetics
before accepting the changed contours. Once the correctness of the incisal edge
positions, labial contours, and lingual curvatures has been verified and accepted
by the patient, the permanent restorations can be fabricated with confidence.
All the information must be preserved in a usable manner, however, so that the

113

finished anterior restorations duplicate the contours that have been tested in the
mouth and confirmed as correct.
Lateral anterior guidance:
Reason for not using the term "incisal guidance" is that the connoted limitation
to the four incisors is often confusing. Incisal guidance is frequently described
in terms of protrusive movements only. Actually, [be lateral pathways that are
established on the anterior teeth have a far greater influence on posterior
occlusal form, and the cuspids play a major role in determining the lateral
stress-bearing capabilities of all the anterior teeth.
The occlusal contours of all the posterior teeth are dictated by both condylar
guidance and anterior guidance. No posterior tooth should interfere with either
anterior guidance or condylar guidance. Posterior teeth may either be discludcd
from any lateral contact by the anterior teeth or they must be in perfect.
harmonious group function with them and the condyles. Either way, the
anterior guidance, as a determinant of posterior occlusal form, must be
perfected before occlusa! contours can be finalized.
Whenever it is practical to eliminate posterior contact while working out the
anterior guidance, it is helpful. This can be accomplished in mouths that require
posterior occlusal restorations by completing the preparation of the posterior
teeth prior to working out the anterior guidance. If the posterior teeth do to
require restorations, the anterior guidance musi be worked out simultaneously
with equilibration of the posterior teeth.
Since the anterior guidance is a protector of the posterior teeth, our goal is to
make the anterior teeth as strong as possible so that they may carry out their
protective function. Adjusting the anterior inclines when there is no support
from posterior teeth enables us to fully evaluate the stress resistance
capabilities of the anterior teeth and to correct them accordingly.

114

The ultimate goal of a correct anterior guidance is that is should be
comfortable, functional, and stable even without posterior contact.
After the anterior guidance is perfected to the optimum degree possible, it can
be determined how much help is needed from the posterior teeth.

If the

anterior teeth are strong enough to function on their own, posterior contact in
centric relation may be sufficient. If the anterior teeth are weak in resisting
lateral stresses, ihe posterior teeth may be brought into group function to help
share the load of lateral forces. If the anterior guidance has been optimally
corrected and is still too weak to serve its protective requirements, splinting
may be necessary to bring the anterior teeth up to the necessary strength.
Close observation of the anterior teeth in the mouth is the best way to
determine whether lateral movements are stressing them. Both visual and
digital examination should be used to determine whether any teeth are being
moved during lateral excursions. Noting the contact areas between the cuspid
and the lateral incisor during lateral excursions is often a good indicator of
stress. Movement of the cuspid will frequently open the contact as the jaw is
moved laterally.
Upper anterior teeth that are noticeably moved by any functional excursion
should be corrected. Correction usually consists of reshaping the upper lingual
contours. Centric stops should always be established prior to refinement of
excursive inclines, so the lower incisal edges are rarely involved in the
correction of any lateral excursion interferences. Changes in the lower anterior
teeth should be limited to minimal adjustments that do not involve the centric
stops on the incisal edges.
Correction of upper lingual contours is patterned to accomplish two effects: redirection of force's and improved distribution of forces. Forces are redirected
by changing the shape of the contacting surfaces. The main vector of force is at

115

a right angle to the surface contacted. Changing the surface changes the vector.
The main vector of force against a steep incline is directed nearly horizontally.
Changing the steep incline to a flat incline would redirect the forces more
nearly up the long axis(fig-39&40).
Improved distribution of forces is accomplished by bringing more teeth into
simultaneous contact during excursions. This is often accomplished as a side
benefit when force direction is improved, because more anterior teeth are
brought into lateral function as steep convex inclines are changed to concave.
In mouths with poor periodontal support, poor crown root ratios, poorly shaped
roots, or poor quality alveolar bone, drastic changes in contour may be
necessary. To reduce stresses to the minimum, it is almost always necessary to
both redirect and redistribute all lateral forces on the teeth.
Correction of upper lingual contours is accomplished by reducing the steepness
of any inclines that, when contacted, cause the tooth to move. Steep inclines
just lateral to the centric stops are the most common source of stress. The need
for corrective flattening from centric stops out is greatest close to the stops and
then diminishes as the jaw moves laterally. This most often produces concave
lingual inclines that are flattest near the centric stops but may then curve into
quite steep inclines to permit effective incising.
It is almost never necessary to reduce the length of an esthetically correct
100th. It is not necessary to flatten the lateral or protrusive angles all the way
through ihc teeth to reduce stress. To do so in protrusion is esthetically
disastrous, and the resultant reverse smile line "ages" the patient many years. If
lateral stresses cannot be minimized enough with concave contouring of upper
lingual inclines, it would be better to stabilize the anterior teeth by splinting
than to ruin the appearance of a person's smile.

116

The determination of whether splinting is needed or not is dependent on
whether or not an esthetically acceptable anterior guidance can be worked out
that does not stress the anterior teeth to noticeable movement when firm
excursions arc made.
It may be quite surprising how practically the correct concave inclines can be
worked out in the mouth. As the mandible moves laterally, the orbiting condyle
moves downward and the natural tendency of the jaw is to open as it moves to
the side. The resultant over and down movement of the lower anterior teeth
produces the concavity in the upper lingual contours, which permits lateral
function with minimal stress.
An anterior occlusal problem that will iiavc to be solved quite often involves
hypcrmobile cuspids in a cuspid - protected occlusion. The lingual incline of
the cuspids is too steep to permit any other tooth inclines from sharing the
lateral stresses. Very often the cuspid inclines are convex, which forces the
cuspid laterally when the jaw moves to the side. If very little bone has been lost
around the cuspids, it may be possible to eliminate the hypermobility with
minimal changes to the cuspids. Changing the convexity to a straight steep
incline with just a little concavity at and just lateral to the centric stops may
solve the problem and be very compatible lo a vertical envelope of function.
This may sometimes be accomplished without even bringing other teeth into
group function. Slight changes very often make major improvements in
function and stability. Making such corrections in the mouth, where patterns of
tooth mobility can be observed, enables us to keep changes to the minimum.
The cuspid with steep or convex lingua! inclines that has lost a considerable
amount of bony support will need to have the inclines opened out to allow an
almost flat area from centric relation laterally to accommodate the lateral side
shift of the mandible (Bennett) and to permit other anterior teeth to come into
group function with it. As more teeth are brought in to share the lateral stresses,

117

the that inclines can then curve into sleeper ones to produce the concavity. At
the same time, the mobility of the cuspid will diminish until even moving the
mandible laterally with firm help from the operator will not cause noticeable
movement of the teeth.
Bringing more anterior teeth into group function not only distributes the
stresses over more teeth, it distributes them to teeth that are progressively
farther from the condylar fulcrum and in a better position to withstand the
stresses. It is often possible to extend group function around to include both
central teeth, and sometimes even the balancing side lateral incisor can
contribute support.
While concave lingual contours usually work out quite naturally for normal to
deep overbite patients, they may be contraindicated for patients with minimal
overbite. The near end-to-end anterior relationship will end up with an anterior
guidance that is almost flat. Lateral guide pathways may have no curvatures at
all. As long as the inclines permit firm excursions without noticeable
movement of teeth, the centric stops are stable, and the esthetics and function
are acceptable, all requirements for the anterior guidance have been fulfilled.
When anterior guidance inclines must fellow fairly straight paths, better
esthetics usually results from having protrusive inclines that are steeper than
lateral inclines. This gives the upper smile line a more natural curvature. Flat
protrusive paths in combination with steeper lateral paths accentuate the
cuspids and produce a harsh, unesthetic, reversed smile line.
Steps in harmonizing the anterior guidance:
Preliminary Steps:
1. When indicated, lower anterior teeth should be reshaped or restored first.

118

1 All posterior occlusal contact should be eliminated {if posterior occlusal
reconstruction is indicated). When the occlusal surfaces oi'lhe posterior teeth
are lo be restored, it is advantageous to prepare them before harmonizing ihe
anterior guidance. Taking ihc posterior teeth out of contact eliminates their
proprioceptive influence and makes it simpler to record centric relation slops
on the anterior teeth. Functional border movements are more easily and more
accurately harmonized since there arc no restricting influences from posterior
proprioception.
The four steps to harmony:
Step 1: Establish coordinated centric relation stops on all anterior tceth(fig-4I):
The dentist must manipulate the mandible and guide it into a terminal axis
closure, marking with thin silk marking ribbon and adjusting until each layer
incisor makes a definite mark. In most mouths, minimal adjustment is required
to establish good centric stops.
Some of the common problems faced at this step are following. Deviation from
first centric contact into a more closed position: All interferences should be
eliminated so that the mandible may close all the nay to maximum closure
without any deviation. This is the most common problem and the easiest to
solve. No contact on some teeth after deviation is eliminated: This is the patient
who has solid centric steps, but not on all teeth. What do we do with the teeth
than are not in contact? We have three choices.
1.

We can close "he vertical by grinding down [he centric stops until all teeth

contact. This ma> sound harsh, but a slight closure of vertical does no harm. In
teeth with severe bone loss, it may have an advantage hy improving the crownroot ratio. Even with firm teeth, slight closure to gain contact is usually better
than having to restore teeth to contact.

119

2.

We can build up teeth to contact it is often necessary to make temporary

restorations to build out the lingual contours into contact.
3.

We can do nothing. Sometimes nothing is what we should do. Anterior

teeth that arc not in contact but that are stable because of a substitute contact
such as lip or tongue position are sometimes better left as they are. We must
just be certain that they are stable without tooth contact before selecting to
leave them that they are stable without tooth contact for electing to leave them
that way. If noncontacting teeth need lo be restored and if we can establish
enough centric stops from other teeth to program, the customized guide table,
we do not have to worry about missing contacts. The restorations can be
corrected on the articulator.
Missing anterior teeth: This problem is solved by making a temporary
anterior bridge from articulated models and then finalizing all contours on the
temporary bridge in the mouth. Correct esthetics can be established right along
with correct lingual contours.
Arch relationship problems that do not allow centric contact on all teeth: As a
general rule, we must determine which teeth should contact in centric relation
before proceeding to the next step. If lower anterior teeth need to be moved or
reshaped, their position and contours must be corrected before proceeding with
finalizing the anterior guidance.
Habits that keep anterior teeth from contacting: Before any noncontacting tooth
is brought into contact, we must make sure it is not being held out of contact by
an unbreakable habit. Many habits of lip biting actually result from
unconscious attempts to cushion the teeth from interfering contacts. Such
habits usually disappear when the occlusion is corrected. Equilibration
procedures should be carried out to produce as much stability as possible prior

120

to preparation. Any anterior teeth that could touch but do not should be
evaluated carefully before they are brought into contact.
Contouring the centric stops: It is necessary for the entire incisal edge of the
lower incisors to contact in centric relation. This usually produces too much of
a ledge in the upper teeth. If upper contours are rounded, contact with just the
labial portion of the incisal edge is sufficient. The shape of the upper contacts
should direct the forces as near up the long axis as possible, but contacts on
slight inclines are not as stressful as they may seem because the labial vector of
force is counteracted by inward pressure from the lips. Posterior support that is
harmonized to the anterior stops will also minimize the potential stress.
When all centric stops have been refined, each tooth should be checked
digitally to make sure it is not being moved by centric closure.
Step 2: Extend centric stops forward at the same vertical to include light
closure from the postural rest position:
This is when we determine how much long centric the patient requires. After
centric stops have been established by manipulating the mandible into terminal
axis closure, the patient should sit up in a postural position. The headrest is
removed and the patient is instructed to tap lightly with the lips relaxed. Red
silk ribbon is inserted between the teeth and the tapping is repeated. The mouth
should be held open while the patients returned to the supine position and a
manipulated centric closure into a darker marking ribbon made (green or blue
works fine). If the red marks extend onto inclines forward of the centric marks,
the centric stops should be extended at the same vertical so that the teeth can be
closed either into centric relation or slightly forward of it without bumping into
inclines. The amount of freedom from centric relation required rarely exceeds
0.5 mm. Regardless of the amount needed, it can be determined quite precisely
by following this procedure.

121

Extension of the centric stops is accomplished nice!) with sharp inverted cone
carborundum stone. Care should be taken not to touch the centric stops them
selves. The results should be checked digitally to make sure that no teeth are
jarred when the patient taps.
Step 3: Establish group function in straight protrusion:
Before protrusive pathways can be established, the precise location of each
incisal edge must be determined. For simplicity's sake now, we will assume
that all the aspects of lip support, phonetics and esthetics that dictate incisal
edge position are correct. If so, all we need to do is selectively grind from the
centric and "long centric" stops forward to the incisal edges. In most cases the
four incisors fall right into group function as individual tooth interferences are
reduced. All reductions should be done on the upper teeth. Interferences are
marked by sliding forward on marking ribbon from centric to end-to-end. If
one tooth marks by itself, the marked area is hollow ground until the second
tooth shared the load and on until all four incisors have continuous contact
forward(fig-42).
At the completion of the protrusive movement, the incisal edges of the lower
central incisors should meet the incisal edges of the upper centrals.

If the

lateral incisors can also meet edge to edge, so much the better, hut it is not
always possible without ruining the esthetics.
Step 4: Establish ideal anterior stress distribution in lateral excursions:
It is wrong to think that every mouth should have anterior group function in
lateral excursions. It is just as big a fallacy as giving every mouth cuspid
protection. However, if the cuspid is showing signs of hypermobiliiy.
accelerated wear, or loss of periodontal support, both stress and wear can be
diminished by bringing it into group (unction with other anterior teeth. While it
is often advantageous to change a cuspid-protected occlusion to anterior group

122

function, there appears to be no sound reason for changing anterior group
function to cuspid protection.
The procedure for customizing the lateral anterior guidance starts with closing
the mandible into centric contact. With firm help from the operator, the patient
is asked to slide his jaw laterally and any movement of any teeth is noted. The
excursion is repeated with marking ribbon interposed between the teeth and the
marked lateral contacts selectively ground until there is continuous contact
from centric to the incisal edge of the upper cuspid.
To reduce the lateral stress on any tooth or teeth, the contacting surfaces must
be flattened from centric contact laterally. However, it is not necessary to
extend the flat surface all the way through the teeth, The cuspid is the key tooth
in lateral excursions, and as the jaw moves laterally on a fairly flat plane, teeth
in front of the cuspid begin to share more of the load. This permits the lateral
lingual inclines to be gradually steepened, forming concave pathway. The
downward excursion of the balancing condyle also contributes to a tendency
for a natural opening movement as the jaw moves laterally to form a concave
over-and-down pathway of the lower front teeth.
For best esthetics, protrusive inclines are almost always steeper than lateral
inclines.
Once the dentist and the patient have accepted the anterior relationship as
correct, we are ready to capture that relationship so that it cannot be lost. We
must duplicate it carefully.
There are a number of ways of accomplishing this. Making a customized
anterior guide table is a most effective yet simple method of transferring the
guidance pathways to an instrument. It can be used with any instrument that
has an anterior guide table.

123

Customized anterior guide table(fig-43):
The customized anterior guide table is only needed when anterior teeth are
being restored. If anterior teeth are not being restored, the teeth themselves (on
the models) act to guide the front end of the articulator when the posterior teeth
are being fabricated.
If both the anterior and the posterior teeth are to be completely fabricated on a
fully adjustable articulator. the condylar guidances must all be set prior to
making the custom guide table.
If the border movements of the posterior teeth are to be recorded directly
through functionally generated path techniques, there is no need to precisely
duplicated condyle pathways on the instrument. The result of condylar
pathways will be captured three dimensionally by the functionally generated
path technique at the site of the teeth themselves.
If the functionally generated path technique for later fabrication of the posterior
teeth is chosen, the condyle paths may be set on the articulator arbitrarily. A
practical approach is to set the horizontal path at 20 degrees and the lateral
setting at 30 degrees. Condylar settings cannot be changed after the customized
anterior guide table is fabricated.
Method of Fabrication:
1.

After the anterior guidance has been finalized in the mouth, upper and

lower impressions are made.
2. Using indentations in the bite record of posterior teeth only, a centric bite
record is taken.

If the posterior teeth have be<*n prepared, the centric bite

record can be taken at the correct vertical dimension with the front teeth
touching.

124

3. After the centric bite record and the impression of the harmonized anterior
teeth are completed, the preparation of the anterior teeth is begun. The model
of the prepared anterior teeth should fit into the same bite record made before
anterior preparations were completed. This will make the model of the
harmonized anterior teeth and the model of the prepared anterior teeth
interchangeable on ihe articulator.
4.

With the model of the harmonized anterior teeth in place, the anterior

guide table is flattened to 0 degrees and the special guide pin is raised about 1
mm.
5.

Special acrylic with dialomaceous earth added is mixed and placed on the

guide table and the articulator is closed. When the anterior teeth are in centric
contact, the guide pin should indent about 3mm, into the doughy acrylic. The
teeth on the upper model should then be slid over the lower anteriors from
centric relation through protrusive and lateral excursions. As the front of the
upper model is guided through all excursions from straight lateral to straight
protrusive, the guide pin forms its own pathways in the acrylic on the guide
table. The acrylic is then allowed to harden.
A customized guide table formed in this manner is in precise harmony with the
guiding lingual inclines of the upper anterior teeth. As long as the condylar
pathways are not changed, the anterior guide pin, sliding on the custom
guidance inclines, will produce the same movements of the upper bow of the
articulator whether the model is on it or not. If the model of the prepared
anterior teeth is mounted in exactly the same position as the model of the
harmonized teeth, its pathways will be identical. This is of course
accomplished by using the same centric bite record to mount both models.
When the customized guide table is completed, it should be checked for
accuracy by making sure that during excursions the upper teeth maintain

125

contact with the lower teeth and that the pin maintains contact with the guide
table.

126

THE PRINCIPLES OF OBTAINING OCCLUSION IN OCCLUSAL
REHABILITATION
The restoration of occlusion requires a correlation and integration of biologic
factors, mechanical principles, and esthetic requirements with treatment
procedures. The objectives of such dental service may be satisfied to a high
degree by several excellent methods of approach.
The unit area concept in the restoration of occlusion for the individual
rehabilitation problem should not be confused with segment of the arch
techniques. The construction of fixed partial denture restorations has been
influenced largely by the materials available through the years.
Within recent years, the segment of the arch procedure has been generally
discarded in favor of techniques with complete arch casts. This technical
improvement has been responsible for the elimination of many of the
inaccuracies which formerly complicated the restoration of occlusal harmony,
even in short-span restorations.
The unit area concept:
With this background, unit area concept in occlusal rehabilitation can be
differentiated from a mere technical procedure used in the construction of fixed
"bridges.'" Basically, the unit area concept is the original method of handling
the involved problems in occlusal reconstruction improved by many
refinements developed in clinical dentistry. The improvements have not been
all technical in nature since emphasis has continued to be placed on the value
of conservative dental treatment for the patient. Further, it is no* necessarily
the most direct approach to the treatment for the total restorative problem.
However, the benefits realized are the preservation and use of jaw relation
landmarks, the conservation of tooth structure in the choice of retainers, the

127

construction of the restorations by the dentist even when auxiliary technical
assistance is not available, the simplified correction of inaccuracies, and the
more efficient management or complicated restorative problems.
Diagnosis:
Preoperative plan of treatmcnl is very important in any method of restoration,
but is indispensable in the unit area approach. While the lower arch may be
restored first for most patients, it is frequently of greater advantage and
necessary to initiate treatment many limes in the upper arch. The factors to be
considered in making this decision arc the existing occlusal plane, the amount
of freeway space (interocclusal distance), the size and location of edentulous
areas, the number, position, and quality of teeth in each arch, the health of the
supporting tissues, and the subjective symptoms.
The elimination and correction of occlusal disharmonies are prerequisites to all
restorative treatment. Harmony must be created between occlusal position and
centric relation, thus establishing centric occlusion. The information necessary
for this prerestorative mouth preparation is obtained from an analysis of the
existing occlusal relation. While it is possible to detect gross irregularities and
interceptive occlusal contacts clinically a detailed study of the occlusal contact
relations must be made on mounted complete upper and lower casts. It is very
important that a thin wafer-type centric relation record be used to relate the
casts. The mounting on an adjustable articulator requires a face-bow transfer
and the wax inter occlusal records to set the condylar guidances.
Questions:
The specific questions to be answered in this discussion are I) Do you use a
hinge bow to register &K hinge axis? Why? (2) How do you record the
occlusa! vertical dimension? (3j How do you record centric relation? (4) What

128

eccentric interocctusal records do you record? (5) How do you establish the
occlusal plane? (6) How do you form cusps?
Summary:
The unit area concept in the application of fundamental principles in occlusal
rehabilitation provides a good practical approach to restorative treatment. Since
the total treatment can be extended over a long period of time while
masticatory comfort is being maintained for the patient, an opportunity to
observe tissue reaction in the restored region is provided.
The lerm "Functional Occlusion" refers to any tooth contacts made within the
functional size of opposing tooth surfaces, or as Schweitzer defined it, as. such
arrangement of teeth as will provide the highest efficiency during all of the
excursions of the mandible which arc necessary to the function of mastication.
In occlusal rehabilitation, we attempt to develop an acceptable functional
occlusion as our end result. Many articulators have been devised in an attempt
to record the many craniofacial, maxillomandibular, and muscle-tcndon-joint
relationships that influence and relate to the occlusal harmony of the
masticatory apparatus. Despite outstanding accomplishments in the articulaior
field, the claim that the mouth itself is the most accurate articulator is still
valid.
Principles and basic laws:
There are two important and basic steps, which must be recognized in FGP
technique and then should be recognized in any technique. These are (I) a
preliminary equilibration of the occlusion, and (2) the establishment of the
incisal guidance. The basic principles of occlusion must be understood and
observed, and definite objectives must be visualized and achieved wherever
possible.

129

The objectives of the preliminary occlusal equilibration are: (I) to correlate .
centric occlusion with the unstrained centric relation, (2) to obtain the
maximum distribution of occlusal stress in centric relation, (3) to retain the
vertical dimension of occlusion. (4) to equalize the steepness of similar tooth
inclines in order to distribute eccentric occlusal stresses evenly, (5) to establish
smooth guidance tooth inclines, (6) lo reduce the steepness of inclines of
guiding tooth surfaces so that occlusal stresses may be more favorably applied
to the supporting tissues. (7)io retain the sharpness of cutting cusps, (8) to
increase number and size of food exits, and (9) to decrease the size of the
occlusal contact surfaces.
Classification and treatment:
There are four classifications of occlusal rehabilitation and situations, and each
requires a different type of treatment: (I) The curve of Spee (occlusal curvature
of the posterior teeth) and the incisal guidance are acceptable as presented by
the patient, but the posterior teeth need rehabilitation. The treatment plan
includes the restoration of the lower posterior teeth to the patient's curve of
Spee. as presented. Then the upper posterior teeth are restored by the
functionally generated path technique. (2) The curve of Spee (occlusal
curvature of the posterior teeth) is irregular, but the incisal guidance is
acceptable. The treatment plan involves the restoration of the lower posterior
teeth to a more desirable curvature with the use of the P.M. instrument. Then
the upper posterior teeth are restored with the functionally generated path
technique and the existing incisal guidance. (3) The curve of Spee (curvature of
the occlusal plane of the posterior teeth) and the incisal guidance are both
unacceptable. The treatment plan involves: (a) the correction of the incisal
guidance by restoring the upper anterior teeth by means of jackets or pinlays as
indicated, (b) the restoration of the lower posterior teeth to a more desirable
occlusal curvature, using the P.M. instrument, and (c) the restoration of the

130

upper posterior teeth with the use of the functionally generated path technique.
(4) The curve of Spec (curvature of the occlusal plane of the posterior teeth)
and the incisal guidance are not acceptable, and the upper and lower anterior
teeth need rehabilitation. The treatment plan involves: (a) (he restoration of all
the lower anterior teeth, (b) the restoration of the upper anterior teeth and the
incisal guidance, (c) the restoration of the lower posterior teeth to a more
acceptable occlusal curvature with the P -M. instrument, and (d) the restoration
of upper posterior teeth with the use of the functionally generated path
technique
Diagnosis:
The diagnosis is made from all possible prediagnostic procedures, such as
intraoral and temporomandibular joint roentgenograms. two sets of diagnostic
casts mounted on a Hanau model H2 articulator, and one set of diagnoslic casts
mounted or. a P.M. instrument. All of these casts mounted with cast relator
(face-bow) registrations and wax interocclusal records.
The Class 4 rehabilitation siluation occurs most frequently. In these patients,
the incisal guidance and the curve of Spee both need changing. The upper
anterior teeth need crowns or pinlays to change the incisal guidance (usually to
make it less steep), and the upper and lower posterior teeth need occlusal
rehabilitation. In planning the incisal guidance, we can reduce its steepness by
reducing the length of both the lower and upper anterior teeth. If, for esthetic or
other reasons, this cannot be accomplished, the incisal guidance can be reduced
by making parallel vertical pinlays.
Treatment plan:
Plan the treatment before any tooth is prepared, just as an architect has his
plans finished before the building is started. Bliminatc any deflective or
interceptive occlusal contacts in centric occlusion. Prepare the upper anterior

131

teeth first, and make complete arch reversible hydrocolloid impressions of the
upper and lower teeth. Mount the casts on a Hanau H2 articulator, which has
straight-line incisal guide table (not convex or concave), by means of a cast
relator (face-bow) transfer and centric and protrusive wax interocclusal records.
Wax patterns are formed and carved on the preparations to establish the
esthetics and the incisal guide factor. The lingual surfaces of these wax patterns
are carved to create a freedom in centric occlusion (what we, call a long centric
occlusion). Centric occlusion should be an area of contact rather than a point of
contact. Therefore if we establish :he area of contact simultaneously with the
incisal guidance, it will be reflected in posterior tooth restorations through the
functionally generated path technique.
Establishing centric occlusion, on anterior restorations:
Metal strips. 0.5 mm. thick, are inserted in front of the condyie balls of the.
instrument, or the protrusive retrusi\e adjustment (on some instruments) is
extended 0.5 mm. Either procedure will-change the relationship of the casts so
the lower one is protruded 0.5 mm. The wax patterns forming the incisal
guidance are first waxed to this position in all functional movements then, the
metal strips are removed, or the protrusive-retrusive adjustment is returned to
zero (centric relation), and the carvings arc extended lingually to establish the
contacts in centric relation. This procedure provides for uniform contacts of the
restorations in both the protruded relation and the centric relation.
After the anterior wax patterns are completed and cast, the castings are returned
to the articulator and gross adjustments are made. This is done even if full
coverage restorations are used. These adjustments are made prior to baking the
porcelain The finished restorations are sealed in the mouth, and different
colored silk ribbons are used to adjust the restorations until the ideal "long
centric" occlusion, occlusal vertical dimension, incisal guidance, and eccentric

132

relationships have been established on all of the anterior castings. These
restorations are then cemented on the preparations and tested and adjusted
again, if necessary. When the lower posterior teeth are prepared, the anterior
teeth maintain the occlusat vertical dimension and the incisal-guidance, which
then influences the shape of the posterior preparation, the occlusal curvature,
and the cuspal inclines in the lower posterior wax patterns. These factors must
be in harmony with the, incisal guidance.
Summary:
1.

The objectives of occlusal

functional efficiency,

mouth

rehabilitation are optimum oral

comfort,

health,

and esthetics, and they can

be

achieved by the technique described.
2.

The posterior teeth maintain the vertical dimension while the anterior teeth

are being restored.
3.

The anterior teeth maintain the occlusal vertical dimension while the

posterior teeth are being restored.
4.

The

incisal

guide

angle, the temporomandibular joints, and the

mandibular musculature register a functionally generated path.
5.

The restorations exhibit a static occlusal contact of all teeth when the

mandible is in centric relation to the maxillae.
6.

An area of centric occlusal contact is developed to provide freedom of

movement in a horizontal direction while the same vertical dimension is
maintained.
7.

All centric movements, including the Bennet movement, can be exercised

without occlusal interferences.

133

8.

Working side contacts are coordinated with the incisal guide contour while

the potentially damaging nonfunctioning side contacts are eliminated.
Treatment of human beings is still a problem of human variables. There are
indications for cuspless teeth or balanced occlusion, and variations or
combinations of the two in treatment of occlusion for some patients. Whichever
is the treatment of choice, it must be capable of functioning within the pattern
of the patient's own individual functional requirements.
In order to construct such restorations with the knowledge that they will fit
these personal human variables, the restorations must be mechanically related
to the individual. The treatment of occlusion requires instruments and
techniques to determine these relations. The mouth is not a good articulator.
The nonfunctioning mouth which makes voluntary movements does not
necessarily function the same, as it will in the involuntary actions of
mastication. This difference is because.the icinporomandibular joints are
unique, being held together by muscle action and not by ligaments. The
ligaments serve to limit the condylar movements, and the glenoid fossae dictate
the paths which the muscles can make the condyles take. Regardless of
thinking to the contrary, clinical experience has shown that there is a relation
between the lemporomandibular joints and the occlusal form of teeth which the
mouth can tolerate. The purpose of instrumentation is to reproduce these
functional paths of the joints in order that occlusal surfaces which will permit a
benign harmony of teeth, joints, and muscles can be constructed for the
individual patient.
Proprioceptive mechanism and instruments:
The proprioceptive mechanism coordinates these structures so that they can
function in harmonious relation and avoid self-inflicted injury. But it cannot
compensate for disharmonious relationships. The problem in constructing

134

harmonious occlusal surfaces is to transfer to a suitable instrument those
functional relations which will result in a benign action of all of the structures
involved. Therefore, the articulator used in the construction of the restorations
should reproduce the relations in which teeth may contact. The articulator does
not prescribe nor dictate the resloration. but it should enable the dentist to know
how the restoration will function in the mouth. Functional contact of the teeth
results from two simultaneous actions. The mandible rotates to closure around
the condyles, while at the same time the condyles glide from an eccentric
position toward their position in centric relation. It is vitally necessary that we
keep this basic problem in mind. In any involuntary muscular act of
mastication, these two actions always occur simultaneously. The patient cannot
rotate the mandible 10 closure without making bodily movements of the
condyles at the same time. Recent investigations point to the fact that the
reason for this is that the greatest muscle power is exerted in lateral excursions,
or. expressed in different words, the more muscle power required, the wider the
lateral excursion. With less resistance, the patient uses less lateral movement
with the same amount of vertical movement. Whenever the condyles are in the
glenoid fossae when the teeth do come into contact, they glide to and beyond
centric occlusion before opening to make the next lateral return stroke.
Opening and closing axes:
The hinge axis is located in the mandible, and since the mandible cannot rotate
to closure without the condyle gliding, the hinge axis moves when the
mandible moves. As the jaw opens, each condyle rotates on its meniscus and, at
the same time, the meniscus glides in its fossa. The mandible (jaw) opens down
and forward. The resultant of these two actions is an opening axis somewhere
near the angle of the mandible. The patient never opens his jaws successively
alike. Each opening is different from the one before. So this axis is neither
locatable nor reproducible. This axis results from rotation around the hinge axis

135

as it is moving along the condyle path. Therefore, if we locate the axis and the
path it follows, we can reproduce the effect of the opening axis. More
important, the closing axis is not the same as the opening axis. The closing
movement is not the reverse of the opening movement; the action is the
reciprocal. The closing axis is a point in space above the skull. But this is still a
result of the same two simultaneous motions, rotation and gliding, so we can
reproduce the effect of the closing axis in closures of the teeth. Because these
are the changing axes of opening and closing, which result from eccentric paths
of the hinge axis, we must reproduce these eccentric paths in the occlusal
relations of the teeth.
We must differentiate between two terms which are often used A changing axis
is not the same as a moving axis. The opening axis and the closing axis are the
changing axis. They are different every time they operate. The hinge axis is the
moving axis, always moving with the mandible, yet unchanging its relation to
tooth closures. Regardless of how you may accomplish it. whether you locate
the axis or not teeth cannot make harmonious functional contact unless 'hey are
related to the hinge axis, it ;s the relation of teeth to this moving hinge axis
which determines cusp form and position for a given individual. This is a
human variable and this is the way cusps are formed.
Establishment of a correct centric relation, vertical dimension, and occlusa!
plane, all depend upon this relation. The joints do not, per se, directly
determine the shape of the cusps. Correct centric relation does determine the
changing relation of the occlusal plane at a given vertical opening, which will
result in cusps which are harmonious for a given individual. So the hinge axis
alone is not enough to restore an occlusion, but without it we cannot determine
the other relation, all of which are necessary for treatment of the mouth. There
are many techniques for obtaining a centric relation record, equally good in the
hands of various dentists, yet a full occlusal restoration made with a correct

136

centric relation record is rarely seen. Therefore, a technique is not of much
value without an understanding of what is required.
Interocclusal records of centric relation:
Centric relation is the most posterior superior position of the hinge axis. A
centric interocclusal record involves two considerations one of which is the use
of a material in the mouth upon which the patient can bite with his own
muscular force, while maintaining the hinge axis in its posterior terminal
position. For reasons having to do with proprioceptivc mechanism, it is
desirable that the "bite" be made at an increased vertical dimension, with a
minimum of closing pressure applied between the teeth Therefore the "bite"
(inierocclusal record) must be made with a pure rotary closure and mounted on
the hinge axis so that the cast can be closed to the correct vertical! relation to
the maxillae. This is not a natural act. As soon as something is introduced into
the mouth for the patient to bite, the mandible attempts to move into a lateral
protrusive relation. Thus, there is the need for a soft material requiring little
muscular force to be applied on the teeth. To provide resistance so that the
muscles will elevate the condyles without moving into a lateral position, the
chin is glided down and back as the mandible is rising to a closed position, the
guidance provides the resistance to the. closure and does not help the closing.
The patient makes repeated closures against this resistance to elevate and
position the condyles. before lite soft recording material is introduced into the
mouth. A centric interocclusal record should never be made with a single
closure into a static position. The rotary ciosmg is continued as the teeth
penetrate more deeply into the material in which the interocclusal record is
made, but closure to the point of tooth contact is never permitted. If the patient
does "bite through" to tooih contact, the record is discarded and a new one is
made. Many materials and methods for making these records are equally good.
Some work better for some purposes than others in different hands, but all have

137

the same objective; to elevate the condyles to their functional bracing position
and to avoid tooth proprioception and a lateral protrusive inlerocclusal record.
They all are intended to provide resistance to closure outside of the
proprioceptive area, so the muscle action will hold the temporomandibular
joints lightly together.
In the restoration of natural teeth, the dentist has little choice in positioning the
plane of occlusion. The occlusal vertical dimension, the plane of occlusion, and
the formation of cusps are all inseparably related. One factor cannot be
discussed without considering its relation to the others. The vertical relation
depends largely upon what is necessary lo position a plane of occlusion that
will permit the formation of cusps which are harmonious with the
temporomandibular joints and the muscles. The presence of teeth limits the
location of the plane of occlusion and may require a change in occlusal vertical
dimension in order to reduce the height of the cusps so they will be
harmonious, with the temporomandibular joints and still not exceed the
tolerance of the supporting structures.
Against this is the fact that an increased occlusal vertical dimension results in
increased crown-root ratio. One must be balanced against the other, and this, in
turn, may require some alteration in cusp form which will represent the best
balanee between the two. Indeed, balanced occlusion embodies many things
other than simple cross arch prosthetic balance. It means a balance of al of the
factors which enter into tooth contact to produce equilibrium of forces acting
upon all of the structures involved. There is no one, arbitrary cusp form and
relation which is best for all cases.

138

RATIONALE AND TECHNIQUE OF BIOMECHANICAL OCCLUSAL
REHABILITATION
"A physiologic occlusion is one in which the relation between the teeth and the
periodontal tissues is such lhat under occlusal stress no injury is produced by
them and further, the tissues are best able to withstand the forces of occlusion,
without the initiation of pathologic changes in the periodontium."
All teeth are subjected to both vertical and horizontal stresses. The steeper the
cusp, the greater the horizontal loading. Vertical loading distributes the stress
over the entire alveolus and may be increased considerably without
overloading. Horizontal loading acts on the periodontal membrane and bone
regionally and frequently exceeds the normal limits of the tissues.
Optimum occlusion is one in which the relation between the teeth and the
periodontal tissues is such that under occlusal stress the most favorable loading
is achieved, thereby fostering the biologic maintenance of the periodontium.
Bilateral balance versus optimum loading:
The question of bilateral balance in the natural dentition is still a controversial
one. Those who are opposed argue that mastication is a unilateral process, that
bilateral balance rarely occurs in nature, that many healthy dentitions present
without bilateral balance and clinch their argument with the pithy comment of
Prime, "Enter bolus, exit balance."
Jankelson's recent work promises to resolve this hitherto academic question. He
concludes. "The evidence strongly suggests that centric occlusion is the only
tooth contact of any significance that occurs during stomatognathic function.
Evidence of eccentric tooth balance during eating was not found. There was no
evidence that balance of teeth eccentric positions is a physiologic necessity, or
that lack of eccentric balance is less conductive to masticatory function".

139

Although bilateral balance is not essential to masticatory function, it is a most
desirable adjunct to occlusal reconstructions. Here we are dealing with
mutilated dentitions and periodontal breakdown, and bilateral balance serves to
distribute the occlusal loading over more teeth and greater saddle area. This
distribution of loading is probably more important during the nonchewing
movements than in actual mastication. We know that actual chewing function
occupies but one hour a day. and we have also' learned from the work of
Hildebrand. Jankelson, and others, that even in chewing, teeth make only
occasional contact. However, in the twenty-three remaining hours of the day,
the teeth contact innumerable limes: in swallowing, during conversation, and
intensional movements. Mow many of our patients requiring occlusal
reconstruction are completely free of emotional tension which frequently is
attended by clenching, tapping, or gritting of the teeth, although perhaps
unconsciously? It is during these twenty-three hours of nonchewing and
tensional contacts that the teeth are subjected to repeated stress, and it is during
this time that bilateral balance serves to mitigate that stress by wider
distribution of it.
Thus bilateral balance is essential to achieving optimum loading of our
reconstructed occlusion. (Note: Bilateral, balance, as it is used here implies
contact of all the posterior teeth and not a single balancing point or area.)
The optimum occlusa! pattern:
From the preceding it would follow that the optimum occlusal pattern for
rehabilitation is the most shallow intercuspation consistent with bilateral
balance.
What can we do to influence and achieve such an occlusal pattern? In virtually
every reconstruction case, we find it necessary to re-establish correct, centric
relation and/or to restore lost vertical dimension. Both of these changes cause

140

the mandible to be brought downward, decreasing the vertical overlap. This
results in a decrease in the degree of inclination of the incisal guidance.
Judicious grinding and reshaping of the anterior teeth, or rebuilding the
anterior- teeth can achieve further reduction in the jangle of the incisal
inclination. Let us now see how by control of this single factor (the angle of the
incisal guidance) we can drastically influence cusp height. Fig.44 illustrates a
comparative study of two different incisal guide angles with the same condyle
angle, in Fig.44. A (with a 50 degree incisal guide angle) we find that in order
to achieve occlusal harmony, we must build upper lingual cusps (and
conversely, lower buccal cusps) ranging from 32.5 to 41 degrees, and; also we
must build upper buccal cusps (and, conversely, lower lingual cusps) ranging
from 15.5 to 32.5 degrees. In Fig. 44.B with a 0 degree incisal guidance and the
same condylar inclination, we find that we .\eed only build upper lingual cusps
(and conversely, lower bucca) cusps) ranging from 17.5 to 9 degrees, and aiso
that all the upper buccal cusps and all the lower lingual cusps require a 0
degree inclination.
Fig. 44.A is representative of an anatomic articulation. In Fig. 44.D, there is no
interdigitation of cusps, and in gliding from the centric position forward, the
teeth encounter a free path without cusp inclines. Fig. 44.B is representative of
a biomechanic occlusion.
Let us trace these lateral gliding movements in the mouth starting from centric
occlusion and ending in left lateral occlusion as illustrated in the schematic
drawing.
In fig. 44.A" (no Bennett movement present) the working condyle lying in the
mandibular fossa begins to pivot or rotate horizontally (on its vertical axis)
However, due to the upper buccal cusp inclines on the working side, the
condyle is now compelled to rotate on its horizontal axis, dropping the body of
the mandible vertically and allowing the lower buccal cusps to glide down

141

along buccal inclines and assume their cusp-to-cusp relationship. The balancing
condyle glides down along the posterior slope of the articular tubercle, and
come to rest when the working side inclines achieve their lateral contacting
position. The balancing teeth have no influence on the movement of the
balancing condyle except where there is premature contact of these balancing
teeth. The balancing condyle in gliding down the articular tubercle drops the
mandible lower on the balancing side, and therefore the upper lingual cusps
must always be steeper than the upper buccal cusps to achieve bilateral
balance.
In Fig. 44,B'. the working condyle pivols on iti horizontal axis a^ In Fig.
L44.A, but: does not have tn rotate on its horizontal axis to permit the lower
buccal cusps for reach their lateral contacting position, because the upper
buccal cusp inclines, are at zero degrees. The balancing condyle travels as just
described but does not have to travel as far down on the articular tubercle to
achieve its balancing position.
In Fig. 44, A" (Bennett movement preseni). there is some clearance between
the condyle (on the balancing side) and the medial wall of the fossa; as the
mandible glides into left lateral position, the pull of the right external pterygoid
muscle draws the right (balancing) condyle toward the inner wall of the fossa
in the Bennett movement. This carries the mandible and left condyle further
laterally than in Fig. 44.A' where no Bennett movement is present. This shift in
the pivoting center of the mandibular gliding movement, does not appreciably
effect the cusp heights previously-established, but does affect materially the
curvature of all the cusps (upper and lower reorganization, may not the
articulation alter again? Certainly we are all aware of this phenomenon, either
consciously or subconsciously, when you recall your patient to check the
occlusion subsequent to completion of the restorations. You have experienced
this phenomenon when you have found it necessary to touch up or adjust the

142

occlusion many months after the delivery of the restorations. Has there been a
slight depression of the teeth? Has there been a slight movement en masse of
all the teeth and prosthesis? And how about subsequent wear of the prosthesis?
Where the occlusal surfaces had been reconstructed to an anatomic articulation,
the paths of movement are closely bounded by interdigitating cusps. The
slightest change due to reorganization or wear may completely disorient the
articulation: There is no tolerance in the occlusal relationship of an anatomic
articulation; this would be contrary to its very concept. Correction in the mouth
would be extremely difficult if not impossible. Mutilation of the original
articulation would be inevitable.
With the shallow modified cusp as in Fig. 44.B, there is no interdigitation of
cusps. A slight change due to reorganization or wear can be easily compensated
for by a slight adjustment in the mouth. This tolerance factor an important and
added safeguard to the continued success of the rehabilitation.
Decalogue for occlusal rehabilitation:
1. Occlusal rehabilitation is a radical and serious procedure. It should
not be undertaken merely because the occlusal relationship existing does not
conform to preconceived concepts of the normal or ideal.
2. The ultimate standard of normal is functional adequacy. In the presence
of functional adequacy, conservative treatment is indicated.
3. Where pathologic changes in the periodontium are in evidence, and where
mutilation and/or occlusal disharmonies are present, mouth rehabilitation is
indicated.
4.

Where extensive prosthesis is

necessary, occlusal reconstruction is

indicated although no pathosis is evident. It will enhance the success of the
treatment.

143

5. The final judgment of success must be in terms of how well and for how
long the remaining teeth and supporting structures are preserved.
6- There is no evidence that an anatomic articulation is a physiologic necessity.
Chewing efficiency can exist over a wide range of occlusal forms and types of
occlusion.
7. Bilateral balance, although not essential to masticatory function, is desirable in that it serves to mitigate the stresses of nonchewing and tensional
tooth contacts by their wider distribution.
8.

The optimum occlusal pattern for occlusal reconstruction is the most

shallow cuspation consistent with bilateral balance.
9. A reconstructed occlusion cannot be regarded as static; a tolerance factor
to permit simple correction for reorganization and wear is desirable to
safeguard the result.
9. Optimum occlusion {where the relation between the leeth and the
periodontal tissues is such that under occlusal stress the most favorable loading
is achieved thereby fostering the biologic maintenance of the periodontium) is
the goal of occiusal rehabilitation.
Classification and technique of treatment:
The conditions which require occlusal reconstruction may be classified in three
categories:
Class A -Condyles in normal resting position in the fossae, loss of vertical
dimension due to missing teeth, drifting of teeth or abnormal wear of teeth.

144

Class B-Condyles in inferior and anterior (mesial) relation in the fossae,
mutilation of the teeth, loss of vertical dimension or increase of vertical
dimension due to eccentric contact.
Class C- Condyles in superior and posterior (distal) relation in fossae with loss
of vertical dimension.
The technique of treatment is very much the same for all three classes.

145

RESTORING LOWER ANTERIOR TEETH
When planning the restorative correction of any occlusal problem, the first
segment to be completed should be the lower interior teeth. Until the precise
location and shapes of the lower incisal edges are set, there is no practical way
to work out the lingual contours of the upper anterior teeth.
The first consideration in restoring lower anterior teeth should be to determine
the correct location of the incisal edges. While this would ideally be decided on
the basis of providing the most stable centric contact with the upper anterior
teeth.
It is a fairly safe assumption that problems are minimal if the lower anterior
teeth can be made to contact in centric relation at the correct vertical
dimension. It is ideal if the contact is on the cingulum of the upper anterior
teeth, but contact on any part of the upper lingual surface can usually be
adapted to the requirements of good function. Even an end-to-end relationship
can be made functional and stable with minor alteration. Shaping the lower
incisal edge back slightly may be all that is required to provide a protrusive
pathway against the upper anterior teeth.
Even a short horizontal path of the lower incisor teeth against the upper incisal
edges is sufficient to disclude the posterior teeth in protrusion if the occlusal
plane is correct. A flat lateral anterior guidance can disclude the balancing side
because of the downward movement of the orbiting condyle, if cusp-fossae
angles are coordinated.
Sometimes a too steep anterior guidance can be flattened by shortening the
lower anterior teeth and restoring the lingual surfaces of the upper teeth. The
cinguium is brought down into contact with the shortened lower anterior teeth,
making the angle flatter between centric contact and the upper incisal edge.

146

Any modifications of this nature should always be worked out on mounted
models and the changes duplicated in the upper temporary restoration for
refinement in the mouth and testing by the-patient.
Crowded lower anterior teeth present a variety of problems that can be solved
in a variety of ways. The first determination to make is whether the crowding is
really a problem.

It is not an occlusal problem if the teeth are stable and

cleanable
and can function without interference in excursions. It may be an esthetic
problem if the crowding is too noticeable.

However, a slight irregularity of

lower incisors is usually not the esthetic shortcoming that some patients may
think. It is most often better lo keep the slightly crowded condition that it
would be to do unnecessary restorative procedures.
If crowded lower anterior teeth need to be restored for any reason, minor tooth
movement can often be simplified by combining it with the restorative
procedures.
After the alignment is corrected, a temporary restoration can be used as an
esthetic yet very effective retainer for a few weeks while the bone and
periodontal fibers reorganize around the moved teeth.
Combining minor tooth movement with restorative preparation of lower
anterior teeth makes possible a myriad of simplified and practical approaches
to solving problems of irregularity or crowding.
Lower incisors that are locked lingually by a steep incline can frequently be
moved forward by tongue pressure if the upper lingual contour is shaped to
accept it. A single lower incisor that has erupted up such a steep incline into
soft tissue impingement may be corrected by shortening it back to the length of

147

the other lower incisors and then providing a concave stop on the upper tooth
that will allow the lower incisor to move forward.
A lower incisor that has supraerupted up above the incisal edge line of the other
incisors should never be shortened back to correct alignment unless a centric
stop is provided for it. If a centric stop cannot be provided, the tooth must be
splinted to another tooth that does have a centric stop. Otherwise the shortened
tooth will erupt right back up where it was.
Separated lower anterior teeth constitute another "problem" that should very
often be left as is. Separation in itself is not an occlusal problem if the teeth are
stable maintainable, and esthetically acceptable. If the spaces must be closed
for estheiics or stabilization, the corrections should first be made by waxing
against the study model.
If the space between lower anterior teeth is too great to be widened acceptably,
it may be necessary to move the teeth together orthodontically and add a fifth
incisor. The extra incisor presents no esthetic problems and is hardly noticeable
even with close observation.
Worn lower anterior teeth can present some difficult problems to solve if the
wear has shortened the teeth to an extreme degree. The usual tendency is to
assume thai vertical dimension has been lost and the treatment is merely a
matter of lengthening the teeth back to their original length to "restore the lost
vertical". This is a dangerous assumption, such treatment is clearly
contraindicated. As teeth wear, they erupt, taking the alveolar process with
them,
Frequently the cause of anterior wear is a posterior interference that deviates
the mandible forward into an acquired position that causes increased stress and
wear on the front teeth. If the interference is eliminated, it often permits the
patient to close 'on a more retruded arc to the same vertical dimension, with

148

ample room provided horizontally between the upper and lower incisors. The
lower anterior teeth can then be lengthened to regain centric contact and to
restore the worn incisal edges.
If full coverage is indicated, it should be either porcelain jacket or porcelain
veneer. Using acrylic on lower anterior teeth is absolutely contraindicated. The
shape and position of the incisal edges are critical to the anterior guidance, and
once precisely established, they should be maintained just as precisely.
Not all worn lower anterior teeth need to be restored. Even if the wear has
penetrated to the dentin. it may be possible to maintain the incisal edges
without restoration. Lower incisors make contact at their labioincisal line angle.
Even with worn edges, the contact will still be on enamel.
If the dentin is cupped out the enamel around it is intact, restoration of the
cupped area with one of the hard filled resin materials is sometimes a logical
choice of treatment. It is conservative, the esthetics is good, and it does not
preclude the later use of full coverage if it becomes necessary.
Hypermobility of lower anterior teeth frequently results from occlusal stress.
Occlusal

correction

often

produces

amazing

results

in

eliminating

hypermobility completely.
Any hypermobility should be treated as an unhealthy situation and all
necessary steps should be taken to correct it. If mobility patterns cannot be
controlled by combined occlusal and psriodontal therapy, splinting may be
considered.
Lower incisors can be maintained with a higher degree of mobility than other
leeth. If restorative procedures are required on the lower incisors for other
reasons and hypermobility patterns are present, it would be practical to go

149

ahead and splint the restorations rather than having to destroy them at a later
time if the need for splinting was determined.
Lower incisors with extreme bone loss should not be splinted unless they offer
support to other teeth.

It is more practical to replace lower incisors with a

fixed bridge than to splint them if the splinted teeth present problems of
maintenance and offer no advantages to the treatment plan.
The replacement of missing lower anterior teeth requires the same preplanning
as other anterior problems. The teeth should be set up or waxed up tentatively
on mounted models so that the incisal edges arc in the best relationship for
stable centric contact.
Esthetic considerations:
The incisal edges of the lower anterior teeth should form a horizontal line that
is either straight across or slightly bowed up in the middle(fig-45). Regardless
of the slant or shape of the ridge, the line of incisal edges should be horizontal
for the best appearance. An incisal edge line that curves down in the middle is
very unesthetic and is not compatible functionally with properly oriented upper
anterior teeth.
It is not difficult to decide how high the incisal edges should be. The anterior
teeth normally form a slightly convex curve that continues smoothly into the
concave curve of Spee. Simply noting the height of the posterior cusp tips and
relaling them to the anterior teeth is a rather uncomplicated clinical judgment.
The labiolingual position of the incisal edges is also very limited in its
flexibility. The direction of stresses must stay as close to the long axes as
possible, and the teeth must stay within the very narrow confines of the
alveolar ridge, so labiolingual positioning is usually rather clear-cut.

150

Duplicating correct incisal edge position:
Once the precise position of the incisal edges has been established, it should be
duplicated in, the permanent restorations. Preparing every other anterior tooth
and taking an accurate impression gives the technician a simple means of
duplicating not only the incisal edge position but also the exact contours of the
incisal edges. A second impression made after all the lower anterior teeth have
been prepared is used in combination with the model of every other tooth
prepared. Waxups or porcelain jackets made on the first model are transferred
to the second model. They are then used as the guide for completing the
remaining crov-ns on the model with all of the anterior teeth prepared.
In restoring lower anterior teeth, it is important to remember that the incisai
edges are not only the key to correct function and stability, they arc also the
key to natural appearance.
Regardless of the occlusal problem, the correctness of the anterior relationship
should be established before proceeding with the restoration of the posterior
teeth. Most often the lower anterior teeth do not require restoration, but
whatever modification is needed, if any. should be finalized before proceeding
to the next step. If the lower anterior teeth have been correctly analyzed and
needed improvements have been carefully made, it should not be necessary to
make any further changes in them through the completion of the entire
restorative procedures.
RESTORING UPPER ANTEIROR TEETH
No technician, including Ihe dentist who prepared the teeth, can consistently
shape anterior restorations precisely enough unless he is furnished the
necessary information.

151

In order to successfully restore upper anterior teeth, the correctness of the
following information must be verified in the mouth and it must be accurately
transferred to the laboratory bench.
Correct lip support: The tightness or flaccidity of the upper lip plays an
important role in positioning the upper anterior teeth. It plays an equally
important role in maintaining that position. Teeth that are not in harmony with
the lip are not only unstable, they are generally uncomfortable and unesthetic.
Precise incisal edge position: Location of the incisal edges establishes the
correct length of each tooth. In combination with correct lip support, the
labiolingual position of the incisal edges determines the pitch of each upper
anterior tooth. This is an extremely important factor to duplicate with
preciseness. It plays the dominant role in esthetics and is a critical determinant
of optimum function.
Labial contours: Some anterior teeth are fan shaped, some convex. Some are
square, some fan shaped, some have distinctive conlours tiiat give the patient's
smile its particular individuality. Good features should be faithfully preserved
and unesthetic features should be corrected. Position and contours of contact
areas demand careful attention to detail and should never be determined by
guesswork.
Lingual Contours: The anterior guidance cannot be finalized until the precise
incisal edge positions have been located because lingual contours are
determined from centric relation to the incisal edge positions. Evaluation of
lingual contours is the last step prior to preparation.

152

Esthetic consideration:
Esthetics and function go hand in hand. The better the esthetics, the better the
function is likely to be and vice versa. The best esthetic result is a natural
appearance. Conversely, close attention to achieving optimum function almost
automatically positions and shapes the teeth in the best relationship to the lips
and the muscles of facia! expression. Like phonetics esthetic considerations are
actually a helpful determinant in establishing the relationship of the anterior
teeth.
Phonetic considerations:
The relationship of the upper anterior teeth to the lower anterior teeth, the lips
and the tongue has a considerable effect on phonetics. The spatial relationships
used to form certain sounds are the result of long-standing muscle memory
patterns. In spite of patient's adaptability to change, a good rule to follow is:
unless there is a specific need to change inctsal edge position, it should be
meticulously duplicated in an\ anterior restorations.
Whenever any gross change of the anterior relationship is undertaken,
contouring and positioning of the teeth should be evaluated from a phonetic
standpoint. Frequently, minor changes make major differences.
Any decision to change the incisal edge position should be considered a major
decision. While necessary in many cases, it should never be done without full
awareness of the effects resulting from the change.
Changing the incisa! edge position affects the following.
Phonetics: The incisa! edges of the upper anterior teeth should lightly touch the
vermillion border of the lower lip when making V and V sounds. Any change
of incisal edge position changes the spatial relationship of the teeth to the lip.

153

Such spatial relationships are so consistent that they can be used an aid to
determine incisal edge position when it has been lost or destroyed.
Lip support: If the incisal edge position is moved either labially or lingually, lip
support is altered. Of course many times such alterations are an improvement,
but ^rteri lip support is changed, it must be consistent with the lip itself. If the
teeth are moved too far labially, pressure from the lip will try to move them
back. The lower "P w ill hang up under the incisal edges and magnify the
change.
For the sake of comfort, phonetics, and stability, any change of the incisal edge
toward the labial should be made only after thoughtful determination that it is
truly needed.
Moving

the

incisal

edge

toward

the

lingual

frequently

improves

both appearance and function, but carelessly or unnecessarily done it can be
disastrous.
The smile line: Minor changes in the incisal edge position can completely
change a person's appearance.
It is essential to the success of each anterior restorative case that the incisal
edge position be accurately determined and precisely duplicated.
Anterior guidance angles: Since functional movements at the front of the
mouth occur between centric contact and the incisal edge position of the upper
anteriors, shortening the teeth or moving the incisat edges labially would have
the effect of flattening the anterior guidance angle. Lengthening the teeth or
moving the incisal edges lingually has the effects of steepening the angle.
When there is sufficient overjet. it is possible to lengthen the upper anterior
teeth and lo compensate with concave lingual contours.

154

When there is minimal overjet. it is often not possible to lengthen the upper
anterior teeth without steepening the anterior guidance angle. If a sleeper
guidance angle is not compatible with function, the upper incisal edges will
have to be move labially as the teeth are lengthened. When longer anterior teeth
are desired, such changes should definitely be effected in the temporary
restorations first to evaluate the results before the permanent restorations are
completed.
THE PLANE OF OCCLUSION
The plane of occlusion refers to an imaginary surface that theoretically touches
the incisat edges of the incisors and the tips of the occluding surfaces of the
posterior teeth. Instead of flat surface, the plane of occlusion actually
represents the average curvature of the occlusal surface.
There are two basic requirements of a proper plane of occlusion:
1.

It must permit the anterior guidance to do its job of discluding the posterior

teeth when the mandible is protruded.
2.

It must permit the disclusion of all teeth on the balancing side when the

mandible is moved laterally.
It is possible for an occlusal plane to be flat and still fulfill the basic
requirements, but if optimum efficiency in function is the goal, the occlusal
plane will usually have curvatures to it. Better esthetics is in most cases also
dependent on curvatures of the occlusal plane, the perfectly flat plane of
occlusion often being the epitome of artificiality. A flat occlusal plane can even
be harmful, since it can actually create stressful crown-root ratios when the
curvature of the supporting alveolar bone is not matched to a reasonable degree
with the curvature of the occlusal plane.

155

If the reasons for making each curve in the occlusal plane arc understood, it
will become evident that there are number of methods that can be used
effectively to establish a suitable occlusal plane for any given patient. Each
curvature is determined by ihe effects it should produce.
The curvatures of the anterior teeth are determined by establishment of the
esthetically correct "smile line" and its relationship to phonetics and the
functional aspects of the anterior guidance.
The curvatures of the posterior plane of occlusion are divided into (I) an
anteroposterior curve, called the "curve of Spee" and (2) a mediolateral curve,
referred to as the "curve of Wilson". Together, the composite of the curve of
Wilson the curve of Spec, and the curve of the incisal edges is properly referred
to as the curve of occlusion. Popular usage combines both the curve of
occlusion and its relationship to the cranium into the plane of occlusion.
Curve of spee<fig-46):
The curve of Spce refers to the anteropostcrior curvature of the occlusal
surfaces, beginning at the tip of the lower cuspid and following the buccal cusp
tips of the bicuspids and molars and continuing to the anterior border of the
ramus. The importance of this aspect of a correct plane of occlusion is more
easily understood if we note what problems occur with variations of an
incorrect curve of Spec. Curve of Spee too high in posterior: This is the most
common disharmony of the occlusal plane. It can be extremely deleterious to
the supporting tissues of the posterior teeth because it forces the most posterior
teeth to carry the full stress imposed on them by the musculature when the
mandible is protruded. Irregular occlusal plane caused by losl but imreplaced
posterior teeth: The result is a collapsed arch that does not permit protrusive or
lateral excursions without interfering with the tilled or elongated teeth. The

156

effect is the same as a curve of Spee that is too high posteriorly. The protruding
mandible directs the stresses onto the teeth least able to resist it.
When an upper molar has supracrupted into a vacant space between two lower
posterior teeth, the upper tooth should be shortened to permit protrusion of the
mandible without posterior contact. This should even be done if it requires
devitalization of the elongated tooth. The same is true if a lower posterior tooth
has elongated into a space above.
If the terminal tooth on the upper has erupted down distal to the most posterior
lower tooth, it does not present a problem, even though it fails to conform to
the picture of an "ideal" occlusal plane.
Curve of Spee too low posteriorly: Making the distal end of the occlusal plane
too low presents no major problems since it cannot interfere with the basic
requirements of protrusive and balancing side disclusion. If it is grossly
overdone, however, it can create a poor esthetic result, can cause excessive
stress on upper teeth by requiring an unfavorable crown-root ration, and could
conceivably reduce function in some mouths by causing too much separation of
the posterior teeth in protrusion. Cune of Spee too high or low in front: If the
lower premolars are higher than the cuspids, they can interfere with the anterior
protrusive guidance by bumping into the upper cuspids. If the lower premolars
are considerably lower than the anterior teeth. the result is very poor
esthetically.
Curve of Wilson(fig-47):
Since upper posterior teeth normally slant outward and lower posterior teeth
are tilted inward toward the tongue, an imaginary line drawn mediolaterally to
touch cusp tips of similar teeth on each side of the lower arch would generally
be concave. This aspect of the occlusal plane is referred to as the curve of
Wilson.

157

When the mandible moves toward the working side with such a flat anterior
guidance, the rotating, translating condyle permits the posterior teeth on that
side to move almost horizontally toward the check. The lower lingual cusp
must be lowered to prevent it from interfering with the upper lingual cusp.
On the balancing side, the orbiting condyle moves downward as it moves
forward and permits lateral movement without interference to the upper lingual
cusps. The result in the lower arch is buccal cusps that are higher than lingual
cusps and consequently a concave curve of Wilson.
There are two ways of effectively changing the curve of Wilson. The first way
is to change the lateral anterior guidance angle. The steeper the lateral anterior
guidance angle, the higher the lower lingual cusps may be on the opposite side.
One may wonder why we even worry about the height of these lower lingual
cusps if they serve neither as a holding contact nor as a functioning incline, but
they do act as useful grippers of coarse of fibrous foods and consequently they
serve a useful purpose even though they need never be in actual contact.
The second way we may change the curve of Wilson is by changing the length
of the upper lingual cusps. By shortening the upper lingual cusps and flattening
the cusp-fossae angles, we can actually make a flat curve of Wilson. Such an
occlusion can still function without interference and without losing the upper
lingual cusps as centric holding contacts. All that would be lost is the
maximum gripping effect that goes with closely approximating cusps in
excursions.
Establishing the plane of occlusion:
There are three practical methods for establishing an acceptable plane of
occlusion:
1) Analysis on natural Iccth through selective grinding

158

2) Analysis on models with fully adjustable instrumentation
3) Use of Pankcy-Mann-Schuyler methods of occlusal plane analysis
Analysis through selective grinding: if it is possible to eliminate excursive
interferences without losing stable centric holding contacts, the plane of
occlusion is acceptable as it is. There is no need to change an occlusal plane
that permits the anterior guidance to do its job of discluding the posterior teeth
in protrusive and balancing excursions unless centric stops are lost in the
process.
Fully adjustable instrument analysis: Any instrument that can duplicate
condylar border movements can be used to analyze or establish a correct
occlusal plane. Selective grinding and or preliminary waxup of models on such
an instrument will clearly show the outer limits of occlusal plane curvatures as
long as the anterior guidance and condylar guidances are correctly programmed
into the instrument.
Pankey-Mann-Schuyler(P.M.S-) analysis of mounted models: If models are
properly mounted with an accurate facebow record on either a fully adjustable
or a semi-adjustable instrument, an acceptable plane of occlusion can be
determined with extreme simplicity. It should be made very clear that the
P.M.S. technique should not be used to determine whether a tooth should be
restored. It is simply a technique for determining the occlusal plane when all or
most of the posterior teeth have already been diagnosed as needing restoration.
When it has been determined that restoration of all or most of the posterior
teeth is necessary, the P.M.S. technique provides an excellent and practical
method for determining an occlusal plane that will fulfill all of the
requirements of a correct occlusion. The simplest method of implementing this
part of the technique is through the use of the Broadrick Occlusal Plane
Analyzer.

159

Broadrick Occlusal Plane Analyzer:
For mouihs requiring restoration of all or most of the posterior teeth, proper use
of the occlusal plane analyzer will accomplish the following: ]

Preliminary

determination of an acceptable plane of occlusion on the study models as an
aid in treatment planning.
2.

Preliminary determination of the amount of reduction that will be required

when each tooth is prepared.
3.

Extremely simple transfer to the mouth of predetermined preparation

height for each tooth
4.

In the laboratory waxup. simple determination of the height of each cusp

tip. Through such a determination, the curve of Spee and the curve of Wilson
arc automatically established according to the predetermined plan of the
demist.
5.

Predetermination of both the cusp height of the finished restoration and

also the height of each prepared tooth. Thus room for a sufficient thickness of
gold or gold and porcelain can be assured in advance.

The technician never

need be restricted in his occlusal carving because of insufficient tooth
reduction.
6.

A properly predetermined plane of occlusion on the lower arch, which

enables the dentist to
contour

select

virtually any type of acceptable occlusal

scheme (posterior disclusion. group function, and so on) with

complete assurance that the established plane of occlusion will permit it.
Using the Broadrick Occlusal Plane Analyzer:
The so-called flag instrument can be adapted to almost any type of articulator
that will accept a facebow mounting of the upper model. The lower model must

160

be mounted with a centric bite record. By using a scribing caliper, a survey
center is located on the plastic sheet attached to the flag. From that survey
center, an acceptable plane of occlusion can be drawn on the lower model. The
technique was adapted for restorative dentistry by Pankey from original
anthropologic research by Monson. The "Monson curve" was originally
applied to complete denture fabrication, but the practicality of the concept
makes it especially useful for patients needing restoration if it has been
predetermined that all or most of the posterior teeth need to be restored.
The technique consists of the following steps:
1.

After the upper model has been oriented to the articulator by a carefully

taken facebow registration, the mounting is completed and the lower model is
then related lo the upper by means of a centric bite record. When the lower
model has been mounted with stone, the upper model should be removed and
set aside for later use.
2.

The "flag" is secured to the upper bow of the articulator and the plastic

sheet is snapped onto one side.
3. The pencil lead is inserted into one end of the caliper and it is set a! a radius
of 4 inches from needlepoint to lead point. The width of the "flag" is 4 inches,
so it can be used as a convenient guide. The selection of a 4-inch radius may
seem to be a very arbitrary setting. The radius could be varied a little either
way. but the change has so little effect on the occlusal plane that there is
nothing to be gained by it except in unusual cases where there is an extreme
curve to the occlusal plane occurring naturally in an extremely small arch.
4. The point on the lower cuspid from which an cstheticaih pleasing occlusal
plane would emanate is located. This will vary slightly according to the shape
of the lower cuspid, but it is a matter of simple judgment. It will fall
somewhere between the tip of the cuspid and the distoincisal line angle.

161

Generally speaking, the flatter the cusp tip. the closer the point will be to the
line angle. The more pointed the cuspid, the closer the survey point will be to
the cusp tip.

The needlepoint of the caliper is placed against the selected

point on the cuspid and an arc scribed on the flag.

This arc will be referred to

as the anterior survey line (fig«48). The survey center that will be used to
determine the occlusai plane will be located somewhere on this line.
5.

Without varying the radius of the calipers, the point is held againsi the

condyle ball of the arliculator so that it aims through the center of the ball and
another arc that will interest the anterior survey line is scribed. This will be
referred to as the condvlar survey line(fig-49). The "survey center for scribing
the occlusal plane on the lower model is usually at the point where the lines
intersect but the point may be moved up to 1 cm. from the intersect if necessary
to favor either the upper or lower posterior tooth as long as it remains on the
anterior survey line. To determine the acceptability of the intersect as a survey
center, the calipers are turned around, the point pul at ihe intersect, and the
height of the pencil mark, which would be made on the last lower tooth,
checked(fig-50). If too much reduction would be required to make the lower
molar fit into such an occlusal plane, the survey center is moved forward on the
anterior survey line up to 1cm. The occlusal plane may be lowered in the hack
by moving the survey center backward up to 1 cm.
If it appears necessary to move the survey center more than lem forward or
backward to establish an acceptable plane, the faccbow mounting is incorrect.
An error can also occur from an incorrect transfer of the intercondylar distance.
6.

When an acceptable height has been established for the most distal lower

tooth, a line is scribed on the model from that tooth forward to the cuspid.
This line will represent the height of the buccal cusp tips.

162

7. To determine the preparation line, the calipers are opened an amount equal
to the desired occlusal thickness of the proposed restoration (usually about 1
'/2mm) and a second line scribed. This will represent the height of the buccal
cusps after the teeth have been prepared.
8.

Some softened base plate wax is adapted to the buccai surfaces of the

model and the preparation line scribed on the wax. The wax is cut carefully
back to this line and also trimmed along the mucobuccal fold line so that the
wax can be fitted accurately in the mouth against the teelh.

Extra hard base

plate wax is used so that it will not distort when it is chilled and placed in the
mouth. This is called the occlusat plane cutting guide.
9.

When the lower posterior teelh are to be prepared- the cutting guide is

placed snugly against the buccal surfaces of the dried teeth and a pencil line is
drawn on the teeth according to the guide.
10. The wax is removed and an inverted cone diamond is used to cut into the
teeth along the line. The entire occlusal surface of each toolh is reduced down
to the preparation line. The preparation should be about 1 Vimm lower on the
lingual than it is on the buccal to accommodate for the curve of Wilson. It is
possible to make a lingual cutting guide to determine the lingual preparation
line precisely. but it is more practical to just visualize the curve of Wilson and
prepare the teeth sufficiently lower on [he lingual than on the buccal.
1. The occlusal plane cutting guide represents only the preparation height for
the buccal cusps.

The lingual cusp preparation is 1 ½ mm lower. After

reduction for correct cusp height has been completed, il is still necessary to
reduce the central groove area to permit correct cusp-fossae contouring of the
restorations. One must note the steepness of the lateral anterior guide angle to
get a general idea of the steepness of the cusp-fossa angle.

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The steeper the

lateral anterior guidance. The deeper one should hollow-grind the central
groove part of the teeth.
The same procedure that is used for determining the plane of occlusion can also
be used most effectively to establish the correct occlusal plane on the wax
patterns. By using a special wax cutting blade in the calipers, the overwaxed
patterns can be cut back to the correct height. The angle of the blade
automatically produces an acceptable curve of Wilson, making the lingual
cusps lower than the buccal cusps.

164

DETERMINING THE TYPE OF POSTERIOR OCCLUSAL
MORPHOLOGY
There is no one type of occlusal form that is optimum for all patients.
Techniques oriented concepts may work well for the majority of patients, but
the varied problems of stress associated with sick mouths can be solved better
by flexibility of form that enables us to vary the direction and distribution of
forces.
The first objective of occlusal form is proper direction of forces. Teeth can
withstand tremendous force if it is directed up or down the long axis of each
tooth when force is directed parallel to the long axis, it is uniformly resisted by
all of the supporting periodontal ligaments except those at the apex. If the force
is directed rurally, the tooth loses the support from about half of the ligaments
that are compressed and puts almost the entire load on the half under tension.
So the starting point in designing occlusal contours is to shape and located the
centric contacts so that the forces are directed as nearly parallel as possible to
the long axes of both upper and lower teeth.
A perfectly flat occlusal surface contacting another flat surface could be
made :o fulfill this first requirement, but it would not be a very good design for
penetrating or grinding fibrous foods. Proper placement of a sharp cusp against
a flat surface could penetrate foods easily and still direct the forces correctly,
but a single sharp cusp against a flat surface would lack resistance to the lateral
forces that come from the cheeks versus the tongue. The addition of more
contacts is often needed to fulfill the second requiicment of occlusal form:
stability.
The back teeth must do more than simply penetrate food: they must crush it
2nd grind it. To enable them to fulfill their role as grinders they must be able to
work one surface against another in either direct contact or a near miss as the

165

jaw moves laterally and protrusively. To accomplish this, the sharp cusps are
broadened at the base and rounded at the tips.
Since the lower back teeth move as the mandible moves, their contours and the
contours of the teeth they contact must be in harmony with the mandibular
movements. The contours of the back teeth are controlled by the same
determinants that control the border movements of the mandible, namely the
condylar pathways in the back and the anterior guidance in the front. The
condylar pathways are referred to as the posterior determinants and the anterior
guidance is referred to as the anterior determinant of occlusion.
Any posterior tooth can create stress in the entire' mechanism if it interferes
with cither the path of the condyles or the path of the lower anterior teeth
against the lingual inclines of the upper anterior teeth.
In the planning of occlusal contours for each individual patient, a major
determination that must he made is concerned with the distribution of lateral
stresses. There are three basic decisions to make regarding the design of
posterior occlusa! contours:
1. Selection of the type of centric holding contacts
2. Determination of the type and distribution of contact in lateral excursions
3. Selection of most practical method of providing stability to the occlusal
form. Types of centric holding contacts:
There arc three basic ways by which centric contact is usually established. !.
Surface - to - surface contact
2. Tripod contact
3. Cusp tip-to-fossa contact.

166

Surface-to-surface contact(fig-51): We refer to this as 'mashed potato
occlusion". It is the form that results if the articulator is simply closed together
when the wax on the dies is soft. There is never any valid reason for using this
type of contact. It is stressful and it produces lateral interferences in anything
other than near vertical chop-chop function.
Tripod contact(fig-52): In tripod contact the tip of the cusp never touches the
opposing tooth. Instead, contact is made on the sides of the cusps that are
convexly shaped. Three points are selected from the sides of the cusps and each
point in turn is made to contact the side of the opposing fossa. Contacts of the
stamp cusps must be made el the brim of the fossa wall so that all posterior
teeth can disengage from any contact immediately upon leaving centric
relation. Lateral and protrusive disclusion of posterior teeth is essential
whenever tripod contact is used because convex tower cusps cannot follow
normally concave border pathways against upper teeth which are also convex.
Tripod contact is difficult to accomplish but it can be done as long as the
anterior teeth are capable of discluding the posterior teeth in all excursions.
Tripod contact should not be used when lateral stress distribution is best
served by including posterior teeth into group function to help out weak or
missing anterior teeth or when the arch relationship docs not permit the anterior
guidance to do its job.
With tripod contact, any degree of shifting of any tooth produces incline
interference. Since upper and lower arches are usually restored together, even a
minute error in recording or transferring centric relation causes loss of
tripoidism on all teeth.
Tripod contact is extremely difficult or impossible to equilibrate without losing
tripoidism and ending up with contacts on inclines.

167

If tripod contact is so difficult to achieve and has so many limitations, why is it
used? Probably the main reason for the popularity of tripoidism is the
impression that it is so stable if it is properly done. This certainly has been one
of the main reasons for advocating its use. However, there is no scientific
evidence to show that tripod contact is more stable than proper tip-to-fossa
contact.
There are no actual indications for tripod contact. While it can be used
successfully in a large number of patients, it has definite limitations in many
others. It offers no advantages over proper cusp tip-to-fossa contact and since it
is more difficult to achieve, is hard to adjust, and is limited in its use, we would
probably do well to thoughtfully evaluate its practicality.
Cusp tip-to-fossa contact(fig-53): If cusp tips are properly located in the most
advantageous fossae, this type of occlusion offers excellent function and
stability with the flexibility Lo choose any degree of distribution of lateral
forces that is warranted. It is the easiest occlusion to equilibrate. Resistance to
wear is excellent since the centric stops are on the cusp tips, while in working
excursions, contact is on the side of the cusp tips as they travel along the
inclines of the opposing teeth. If disclusion of any tooth is desired in any
eccentric excursion, it is accomplished easily by adjusting Ihe fossa inclines
without disturbing the centric holding contacts.
With cusp tip-to-fossa contact, it is not necessary to restore upper and lower
teeth together.
Cusp tip-to-fossa conlact is not a by-product of any specific technique. It serves
the goal of function rather than form. It can be accomplished with the aid of
gnathologic instrumentation, functional path procedures, or a myriad
of other instrumentation techniques.

The one essential for accomplishing it

correctly is an understanding of what we are after.

168

ProperK done, it can be

beautiful as well as functional and stable. Variations of posterior contact in
lateral excursions:
As the mandible moves laterally, the lower posterior teeth leave their centric
contact with the upper teeth and travel sidc-\\a\s down a path dictated by the
condyles in the back and by the lateral anterior guidance in the front. Each
lower posterior tooth is limited to these border pathway, meaning that they
cannot follow a path from centric relation that is any Hatter or more concave
than the condyles and the lateral anterior guidance permits.
In order to make meaningful judgments about the distribution of lateral stress.
we must first distinguish the difference between the rotating condyle and the
orbiting condylc. Each side has physical characteristics that are important to
understand before and occlusal scheme can be planned with any degree of
dependability. In discussing lateral excursions we divide the movements
accordingly into working side occlusion and nonfunctioning side occlusion
(also referred to as the balancing side).
Working side occlusion refers to the contact relationship of lower teeth to
upper teeth on the side of the rotating condyle. The side toward which the
mandible moves is the working side. The condvle on the working side can be
braced against bone or ligament throughout the working excursion, so it is
possible and quite practical to accurately record and restore the posterior teeth
to precise working side-border movement contacts.
Nonfunctioning side occlusion is the side of the orbiting condvle. When the
condyle leaves its braced position and slides forward down the slippery incline
of the eminentia. it is no longer solidly feed against the unyielding bone and
ligament. Rather, it can move up a little since the mandible bends slightly
under firm muscle pressure. Consequently, tooth contact during nonfunctioning side excursions should not be allowed. Because of the flexibility of

169

the mandible, it would not be possible to harmonize occlusal contours to all the
variations resulting from the differences in muscle force from light to heavy.
Hence we have the rule: wherever lower teeth move toward the tongue, they
should not contact.
The job of discluding the nonfunctioning side is always the responsibility of the
working side.
The dentist must decide how all this is done by selecting one of the following
choices for working side occlusion:
1.

Group function

2.

Partial group function

3.

Posterior disclusion

Group function refers to the distribution of lateral forces to a group of teeth
rather than protecting those teeth from contact in function by assigning all the
forces to one particular tooth.
To paraphrase a law of physics - the more teeth that carry the load, the less load
any one tooth must carry. We must decide which teeth are capable of carrying
how much load and assign the load accordingly.
Group function of the working side is indicated whenever the arch relationship
does not allow the anterior guidance to do its job of discluding the
nonfunctioning side. The anterior guidance cannot do its job in the following
situations:
1. Class II occlusions with extreme overjet.
2. Class HI occlusions when all lower anterior teeth are outside of the upper
anterior teeth

170

3.

Some end-to-end bites

4.

Anterior open bite cases

When using posterior group function the following rule applies: contacting
inclines must be perfectly harmonized to border movements of the condyles
and the anterior guidance. Convex-to-convex contacts cannot be used to
accomplish this.
Partial group function refers to allowing some of the posterior teeth to share
the load in excursions while others to share the load in excursions while others
contact only in centric relation. As an example, a second molar may be very
firm vertically but be hypermobile buccoiingually. Such a tooth should touch
only in centric relation and be discluded immediately.
Anterior teeth with post orthodontic root rcsorption or congenital!; poor crownroot ratios should very often be harmonized to group function with the working
side.
Whether or not any tooth should share the lateral stresses should be decided on
the basis of each tooth's resistance to lateral stress. There is no good reason
why such a decision cannot be made on a tooth-by-tooth basis. If a tooth is
weak laterally, it should contact in centric relation only.
Problems with group function result from improper harmony of the contacting
inclines.
For group function to be effective in reducing stress, the cusp inclines must be
in perfect harmony with the lateral border movements of the jaw. Incline
interferences on posterior teeth get closer to the condyle fulcrum, so a slight
interference on a second molar would probably be more stressful Irian a more
noticeable interference on a cuspid.

171

Posterior disclusion refers to no contact on any posterior teeth in any position
but centric relation. It can be accomplished easily tt ith cusp tip-to-fossa
morphology. It must be accomplished with tripod or surface-to-surface
morphology to prevent lateral interferences in any case with centric contact on
inclines that are steeper than the lateral border movements of the mandible.
There are two methods of accomplishing posterior disclusion:
1.

The anterior guidance is harmonized to functional border movements first

and then the lateral inclines of the posterior teeth opened up so that they are
discluded by a correct anterior guidance.
2.

The posterior teeth are built first and then discluded by restricting the

anterior guidance. This method is backward. Anterior guidance is a proper
determinant of posterior occlusal form and thus should be done first.

When

posterior occlusal form determines the anterior guidance, the correctness of the
anterior guidance is a product of chance.
Posterior disclusion can be achieved by two different types of anterior
guidance: anterior group function and cuspid protected occlusion. Neither is
applicable for all cases.
Anterior group function is the most practical method for discluding the
posterior teeth when arch relationships and tooth alignment permit it. Anterior
group function is beneficial in three ways:
1.

It distributes wear over more teeth

2.

It distributes the stresses to more teeth

3.

It distributes stress to teeth that are progressively farther from the

condyle fulcrum.

172

Anterior group function is extremely comfortable and efficient. It improves the
efficiency of incising movements by providing lateral as well as protrusive
shearing contacts.
When it is impractical to distribute the lateral guidance stresses over several
teeth, disclusion of the posterior teeth can be accomplished by using the
cuspids in one form or another of cuspid-protected occlusion.
Cuspid - protected occlusion refers to disclusion by the cuspids of all other
teeth in lateral excursion. It usually serves as the cornerstone of what is called
mutually protect occlusion. Mutually protected occlusion has been defined in a
number of ways, but the usual connotation refers to an occlusal arrangement in
which the posterior teeth contact in centric relation only, the incisors are the
only teeth contacting in protrusion, and the cuspids are the only teeth
contacting in lateral excursion.
Predominant prerequisite for its use is the capability of the cuspid to withstand
the entire lateral stress load without any help from other teeth. Lateral stress
becomes insignificant if the mandible functions normally within the lingual
inclines of the upper cuspids.
It is impossible to exert excessive stresses against the cuspids in centric relation
because the posterior teeth also resist the stresses in that position, if the
occlusion is correct.
In natural cuspid-protected occlusions, the pattern of function is rather vertical,
so the mandible does not use lateral movements that would subject the cuspids
to stress in that direction either.
Any attempt at lateral movement is felt by the pressoreceptors around the
cuspids. Within limits, these exquisitely sensitive nerve endings protect the
cuspids against loo much lateral stress by redirecting the muscles to more

173

vertical function. As long as the pressoreceptors can keep the muscles
programmed to a vertical envelope of function, there is insufficient lateral
stress generated to harm the cuspids.
Some clinicians have reported that the cuspids have the distinction of being
protected by a greater number of pressoreceptor nerve endings than is found
around any other tooth. This alleged density of proprioceptors is supposed to
impart a unique capacity to the cuspid to redirect any functional pattern that
would be destructive. If. for example, a horizontal chewing cycle would exert
too much lateral stress against
The cuspids, their special proprtoccptive protectors would simply change the
chewing cycle to a vertical, chop-chop function rather lhan let harm come to
the cuspids or their supporting structures. But further research has failed to
substantiate the report [hat there are more proprioccptors around the cuspids
than there are around other teeth. Furthermore, clinical results over a period of
time have shown that the cuspid, just like other teeth, is also subject to the
usual problems of excessive lateral stress if it interference with normal
functional movements. There does not appear to be any valid support for the
cuspid-protection theory on the basis of special proprioceptive capacity to
radically after habitual patterns of function.
However, there are other valid reasons why cuspid-protected occlusion works
well for many patients. The cuspids have extremely good crown - root ratios,
and their long fluted roots are in some of the densest bone of the alveolar
process. Furthermore, their position in the arch, far from the fulcrum, makes it
more difficult to stress them. In short, they are very strong teeth. If their upper
lingual inclines are in harmony with the envelope of function, they are usually
quite capable of withstanding lateral stresses without help from other teeth.

174

The natural cuspid-protected mouth is easily distinguished by convex or very
steep lingual inclines on the upper cuspids. For simplicity, cuspid protection
can be divided into two categories:
1.

Posterior disclusion by cuspid inclines that are in harmony with functional

border movements.
2. Posterior disclusion by cuspid inclines that restrict mandibular movements
within habituai functional border movements.
Restrictive cuspid protection is usually used as an attempt to avoid stressful
posterior contact in lateral excursion by forcing the patient into a changed
pattern of function.
Selecting occlusal form for stability:
Assuming that cusp-fossae relationships are correctly placed for ideal direction
of stress, we still must make decisions regarding the number of contacting
cusps that are needed for maximum stability under differing conditions. We
generally have four basic types to choose from in normal arch relationships.
Type l(fig-54): Lower buccal cusps contact upper fossae. There are no other
centric contacts. Working side excursive function is limited to the lingual
inclines of upper buccal cusps.
If desired, continuous contact can be maintained in working excursions on the
lingual incline of the upper buccal cusps, or if disclusion of posterior teeth is
desired, it can be easily accomplished by modifying the upper inclines.
Disclusion of balancing inclines can be easily accomplished.
The only apparent disadvantage to this type of occlusal relationship is its lack
of dependable buccolingual stability. Pressure from the tongue can tilt the teeth
toward the buccal with very little resistance.

175

Type 2{fig-S5): Centric contact on the tips of lower buccal cusps and upper
lingual cusps. Working side excursive function is limited to the lingual inclines
of the upper buccal cusps. There is no excursive function on any lower incline.
The addition of the upper lingual cusps as centric holding contacts contributes
greatly to the stability of the posterior teeth. Lateral stress toward the buccal is
resisted by the contact of the upper lingual cusps against ihe lower fossae.
Stress to ward the lingual is resisted by the lower buccal cusps against the
upper fossae.
From every clinical standpoint, the performance of this type of occlusal contour
is unsurpassed. It is comfortable and functional and its stability is as good or
better than any other type of occlusal relationship. Because it fulfills all the
requirements of good occlusal form and can be accomplished with clinical
practically.
Type 3{fig-56): Centric contact on tips of lower buccal cusps and upper lingual
cusps. Working excursion contact is limited to the lingual incline of upper
buccal cusps and buccal incline of lower lingual cusps.
This type of occlusal contour is identical to type 2 except thai the buccal incline
of the lower lingual cusp becomes a functioning incline.
There is no clinically discernible advantage in making the upper lingual cusps
contact in lateral function.
The major difference between this type of occlusal form and type 2 is the
difficulty of accomplishing it. In order to bring the upper lingual cusps into
working excursion contact, the buccal inclines of the lower lingual cusps must
be precisely contoured to the exact lateral border movement of both the
condyle and the anterior guidance.
Type 4(fig-57): Tripod contact

176

There are two types of tripod contacts: contact on the sides of cusps and the
walls of fossae and contacts on the brims of fossae and on top of wide cusp
tips.
Contact on the sides of cusps and the wall of fossae: Contact on the sides of the
cusps does not permit any lateral or protrusive movement on a horizontal plane,
so if the anterior guidance has been flattened even for a short distance from the
centric stops to permit a lateral side shift of the mandible, this type of occlusat
form will be contraindicated. It is also contraindicated for any patient who
requires a "long centric".
It may be used in vertical or near vertical functional cycles with either cuspidprotected occlusion or anterior protected occlusion.
Tripod contact is the most difficult of all occlusal forms to fabricate. Centric
contact on the brims of fossae and the top of wide cusp tips with no contact in
eccentric excursions. This type of tripod contact can be made to function with
any type of anterior guidance because it permits horizontal lateral movement
without interference. It is automatically discluded by any anterior guidance
effect other than flat plane, so it cannot be used when posterior group function
is indicated.
There are several types of" occlusal form that can be used to restore posterior
teeth. Whatever contour is selected should be chosen because it:
1.

Directs the forces as near parallel as possible to the long axis of each toolh

2.

Distributes the lateral stress to maximum advantage in varying situations

of periodontal support
3.

Provides maximum stability

4.

Provides maximum wearabUJty

177

5.

Provides optimum function for gripping, grinding and crushing

RESTORING LOWER POSTERIOR TEETH
The lower cup-fossae inclines are determined by the anterior guidance and the
condylar guidance. If the lower lingual cusp is 10 have functional contact in
working excursions, its buccal incline must be the same as the lateral anterior
guidance, with some modifications to maintain simultaneous conformity to
condylar paths. If the lower lingual cusp is to be discludcd in working
excursions, its buccal incline must be Halter than the lateral anterior guidance.
So from a practical standpoint, lower cusp-fossae angles should be Hatter than
ihe lateral anterior guidance.
Posterior teeth in the lower arch can be accurateK restored with cusp tip-tofossa contact if the following determinations can be made:
1. Correct height and placement of bucca! cusps
2. Correct height and placement of lingual cusps
3. Correct placement of fossae
4. Correct inclines for fossae walls
5.

Fairly accurate ridge and groove direction

The starting point for determining lower occlusal contours should be the buccal
cusps.
Placement of lower buccal cusps
Placement of lower buccal cusps is determined on the basis of providing the
optimum effect for buccolingual stability, mesiociistal stability, and
noninterfering excursions.

178

Buccal cusp placement for buccolingual stability: The correct bcation of
each lower bucca! cusp should be one of the first determinations made when
the original treatment plan is outlined. Preparation for restorations should not
be made until the lower teeth are in their most acceptable relationship to the
upper teeth.
The buccolingual position of lower buccal cusps is determined in the
following manner on mounted models: 1. Upper central groove position is
analyzed. On each upper occlusal surface, a line is drawn from mesial to distal
in the central groove. The ideal contact point for each lower buccal cusp tip
should usually be located somewhere on this line.
How ever, the correctness of the central groove should be analyzed on each
tooth.
In some lilted teeth, it is advantageous to move the central groove to gain better
direction of forces through the long axis. If moving the central groove will
enable the stresses to be directed more nearly through the long axis of any
upper tooth, the improved central groove position should be so noted on the
upper model by drawing a new line.
2. Optimum contact for stress direction on lower posterior teeth should
be determined.

While disregarding the upper central groove 1 position, the

buccal cusp position that would most nearly direct stresses down through the
long axis of each lower posterior tooth is determined.
A mark is made on each lower tooth to indicate the position of the buccal cusp
that would be optimum for buccolingual stability and direction of force.
3. The alignment of the optimum lower buccal cusp position against optimum
upper central groove position is evaluated. If the marks do not line up
precisely, the positions of both the upper central groove and the lower buccal

179

cusp tip are equally changes. The new cusp tip positions are rcevaluated to
make certain that they are compatible with acceptable stress direction through
the long axis of each lower tooth. The upper groove position is similarly
evaluated.
If the altered buccal cusp tip position does not provide acceptable stress
directioning for both upper and lower posterior teeth, the arch relationship is
unacceptable and the treatment plan should be designed to correct the problem.
The basic rule to follow regarding the buccolingual position of the lower buccal
cusp is: the lower buccal cusp must be positioned so that its contact directs the
stresses through the long axis of both upper and lower tecth(fig-58).
Mcsiodislal placement of lower buccal cusps:
Two considerations should determine the mesiodislal position of lower buccai
cusps: mesiodistal stability and nonintcrfering excursions.
Attaining mesiodistal stability: The best mesiodistal stability is attained by
placing the lower buccal cusps in upper fossae.
There is no tendency for cusp tips to migrate out of properly contoured fossae.
There will be times wheit it is not practical to place the lower buccal cusp in an
upper fossa, and it will be necessary for it to contact on the marginal ridges of
two upper teeth. Plunger cusp food impact ion can be avoided by proper
design. The upper marginal ridges should be conioured with sluiceways from
the adjacent fossae that permit the crushed bolus to slide away from the
contact.

The contact itself should be wide enough to protect the interdental

papilla.
Incline contacts in centric relation should be avoided. While acceptable toothto-iwo teeth contact can be accomplished, it is usually rather simple to warp the
lower buccal cusp mesially or distally the 1 or 2 mm required to place the cusp

180

tip into an upper fossa. Whenever ii can be done with practicality, this is what
we try to do. Locating the lower buccal cusps for no n interfering excursions:
The mcsiodistal placement of each lower buccal cusp is determined by locating
it in the fossa that permits excursions from centric relation without interference.
By first selecting appropriate fossae on the upper mounted model, the paths of
the lower cusps from each fossa can be quickly determined since they will
travel at right angles to the rotating condyle(fig-59).
It is not necessary at this time to consider the side shift of the mandible. Its
effect will be primarily on ridge and groove direction and fossae contours that
will be compatible with this method of selecting cusp tip position.
If stress direction is acceptable to both teeth, the paths of movement from the
selected fossa should be evaluated. If the lower bucca! cusp can move out of
the fossa in protrusive working and balancing excursions without colliding with
another cups, its position is acceptable.
Placement of the lower cusp tip directly between the upper buccal and lingual
cusps is not only unstable, it also necessitates the destruction of upper occlusal
anatomy to permit excursions.
It is usually best to place the lower buccal cusps of bicuspids in a mesial fossa
when possible. This aliows egress from centric relation through all excursions
with the least chance of destroying tooth anatomy in the process.
Molar cusp tips should be placed so that they will not collide with upper cusps.
They may be placed in the mesial fossa the same as bicuspids, or in the distal
fossa with nonfunctional egress through the transverse groove. Molar cusp tip
placement is also permissible in the jipper central fossa since it can pass to the
mesial of the upper mesiolingual cusp in its nonfunctioning excursion and it
can pass between the buccal cusps in working excursion.

181

Contouring cusp tips:
For cusp tip-to-fossa contact, the tip of each lower buccal cusp should be small
enough to fit into a normally contoured fossa. If the anterior guidance permits a
lateral side shift, the cusp tip should be able to contact the base of the fossa
with out touching the fossa walls in centric relation. If the anterior guidance is
steeper than the fossa walls and no lateral side shift is permitted, the side of the
cusp may contact the fossa walls.
When the tip of the cusp serves as the centric contact, it should be wide enough
to provide optimum wear resistance. It is difficult to be specific about the size
of a cusp tip that would be suitable for all fossae because contours vary as
border palhways vary, but in general the tip of the cusp should have a fairly flat
area about 1mm or so wide. In lateral excursions, if group function is desired,
the side of the cusp contacts the wall of the fossa rather than the tip.
If a cusp tip is to be placed in a fossa, the tip must not be wide mesiodistally.
This is a common fault, and it should be remembered that each cusp must
follow border pathways from its point of centric contact. If a cusp is too wide,
the path that must be cleared for its excursive movements will destroy the
anatomy of the opposing tooth.
Wide cusp tips require more force for bolus penetration and therefore they put
more stress on the supporting structures. Narrow cusps require less force and so
they produce less stress.
Placement of lower lingual cusps:
In normal tooth-to-tooth relationships, the tip of the lower lingual cusp never
comes in contact with the upper tooth. Even though the buccal incline of the
lower lingual cusp be made to contact in working excursions, there is no
apparent advantage in doing so.

182

The lower lingual cusp has another job to do. since it is primarily responsible
for keeping the tongue from getting pinched between the posterior teeth. The
position and contour of the cusp tip should reflect this responsibility without
causing irritation to the tongue. The cusp tip should be rounded and smooth on
its lingual aspect. The position of the tip should have enough lingual overjet to
hold the tongue out of the way, but it should always be located over the root,
within the long axis,
The distance between the lower buccal and lingual cusp tips is the same as the
distance between upper cusp tips, so once the lower buccal cusp tip has been
located, this measurement can be applied to position the lingual cusp. The
measurement between buccal cusp tip and lingual cusp tip should not be much
greater than half the total buccolingual width of the tooth as its widest part. .
Generally the lower lingual cusp height should be about a millimeter shorter
than the buccal cusp. Cusp height can be lowered further in the first premolar.
Contouring the lower fossae:
When it serves as the lateral anterior guidance, the lingual incline of each upper
cuspid dictates the fossa contour of each lower incline that faces it{fig-6O).
• The lateral guidance incline of each upper cuspid dictates the fossa contours
of the buccal inclines of each lower lingual cusp on the same side and the
lingual inclines of each lower buccal cusp on the opposite side. When the
cuspid is not in position to function individually or in group function as the
lateral anterior guidance, the lingual incline of the most anterior upper tooth
that can assume the role becomes the dictator of the lower fossae inclines
facing it.

183

From the contact point of each upper lingual cusp, the lower fossa inclines
should be no steeper than the lateral guidance inclines they face. Any incline
that is steeper discludes the lateral guidance and adds to its own lateral stress.
The simplest and most practical approach is to open up the lower fossae by
providing more than enough freedom for a lateral side shift and making the
cusp-fossa angle flatter than the lateral anterior guidance angle.
Contouring ridges and grooves:
Ridges and grooves give beauty and naturalness to the occlusal scheme. It is
the action of ridges and grooves against their opponent counterparts that grasps
the food and then crushes, tears, and shreds it as the lower teeth follow their
cyclic paths of function against upper inclines.
The arrangement of ridges and grooves is to permit the cusps to pass close
enough to each other to mangle the food between the grooved surfaces without
actual need for tooth contact.
Fairly accurate determination of ridge and groove direction is all that is needed.
Extreme preciseness is not required because in tip-to-fossa contact only the
base of the lower fossa contact the upper lingual cusp. The walls of the fossae
never contact and grooves can be opened out just as fossae are opened out lo
avoid contact.
We must not make the mistake of designing grooves that are slotted so a cusp
can pass precisely through the slot on a given border path. As an example, the
walls of such a groove may allow passageway of the cusp in a lateral working
excursion, but the groove would not accommodate the cusp in a protrusive
lateral path.

184

The direction of any ridge or groove is determined by the path of the lower
tooth as it moves with the mandible. Lateral excursion grooves are at right
angles to a line drawn from the rotating condyle.
WAXING TECHNIQUE FOR LOWER POSTERIOR TEETH
When lower cusp location and fossae contours have been correctly established
on an acceptable occlusal plane, the upper occlusal surfaces may be accurately
restored using a number of different methods including stereographic or
pantographic techniques. Functionally generated path procedures, however, can
be used against such lower occlusal contours with extreme accuracy in the full
range of border movements without loss of the upper lingual cusp as a centric
contact. The correctly placed and contoured cusps of the lower teeth used
against functionally generated pain wax determine not only upper fossa
contours but ridge and groove directions as well.
After the tower posterior teeth have been prepared, the anterior guidance
should be checked for correctness. Impressions should then be made for the
upper opposing model and the lower die models. They should be properly
mounted with a facebow and centric bite record.
Procedure for locating (he buccal and lingual cusp tips:
1.

A line is drawn along the central groove of the upper posterior teeth.

If

some of the upper teeth are badly broken down or missing, it is often helpful to
reshape the upper teeth by carving the stone model or reshaping the teeth with
wax before finalizing the best cusp tip placement.
2. Now, noting the mesiodistal relationship of each lower tooth to its opposing
upper, the most advantageous placement of each lower bucca! cusp is selected.
We should try to select fossae for cusp tip placement whenever possible. Each
spot should be marked.

Buccal cusp top placement will be where each line

185

intersects (FlG-61). The selection of cusp tip placement should be checked by
noting the direction of excursions from each point.
3.

Using a No. 6 round bur, a hole is drilled at each cusp tip location to the

depth of the bur head.
4.

Dark-colored 14 - gauge wax sprues should be cut into 3mm lengths and

inserted into each drilled hole(FlG-62). The articulator should be closed to be
sure the sprue wax does not in interfere with opposing lower dies.
5. With the articulator closed, red inlay wax is flowed around the occlusal part
of the die to engage the dark sprue was.
6.

The articulalor is opened and more wax flowed around the dies until the

crowns are overbuilt. Interproximal contacts between teeth should be as close
to correct as practical in ihis early waxup stage.
7.. The flag instrument (Broadrick Occlusal Plane Analyzer) should be used to
determine the heights of the buccal and lingual cusps through the establishment
of the curve of Wilson (buccolingual curve). The correct occlusal plane must
be determined prior to preparation of the teeth to ensure sufficient occlusal
thickness for all the lower posterior restorations. When the overbuilt wax
patterns arc reduced to the proper line and plane of occlusion the precise
position of each lower buccal cusp tip will show up in the dark wax. After the
plane of occlusion is established, that dark cusp tip is never touched. When this
step is completed, there is no further need for keeping the lower model on the
articulator.

All the steps that follow can be accurately carried out with the

lower model off the instrument.
8.

Buccal anatomy is carved easily now the crest of contour should be

established at about the junction of the gingival and middle third. In waxing

186

full crowns, the contour of the gingival third should start with a concavity
before becoming convex at the junction of the middle third.
9.

Lingual cusp tips are located. The distance between the buccal and lingual

cusps of the lower teeth is generally the same as mat of the upper posterior
teeth. It is a practical procedure to simply measure the upper teeth and transfer
to the lower. A double - pointed caliper can be used to measure the upper lipto-tip distance. One point of the caliper is then placed in the center of the
bucca! cusp tip is noted by making a slight depression in the wax with the other
caliper point(fig-63).
10. Lingual contours can now be carved using the lingual cusp tip location as
one reference and the gingiva! margin as the other.

The crest of contour

should be with in the middle third.
Determining and carving lower fossa contours:
It has one purpose: to ensure a noninterfering accommodation for the upper
lingua! cusps.
The procedure involves making a fossa contour guide that can be used in any
stage of waxup or even porcelain application. The guide should accompany the
articulated die model.
Normally the guide is made before waxup is started but it not used until the last
stage of pattern contouring.
1. The anterior guide table is flattened to 0 degrees and the incisal guide pin
removed. The special pin for making the fossa contour guide is inserted in its
placer It must not touch the metal.
2. A mound of softened wax is made on the flat guide table. Bosworths Tacky
Wax works fine.

187

3.

The special pin is lowered into the wax and the upper model moved into

left and right excursions. The articulator must not go into protrusion. As the
upper bow of the articulator is moved right and left, the lingual surfaces of the
upper cuspids guide the upper model over the incisal edges of the lower
cuspids and carry the special wax cutter pin through the wax on the same path
as the lateral anterior guidance. The resultant angulations or curvatures in the
wax will be in direct relationship to the correct fosse contours.
4. When the lateral guidance pathways have been cut sharply into ihe wax on
the guide table, the special pin in raised and the wax painted with a separating
agent.
5.

The tip is cut off the small end of a plastic protector that comes on

disposable syringe needles. The large end will fit snugly on the raised special
pin.
6. a. Mix of self-curing acrylic is made and some is poured into the indentation
in the wax.
b. Some of the acrylic is wiped up into the hole in the bottom end of plaslic
needle protector.
c. The pin is lowered so that the acrylic is joined. The needle protector will
become the handle for the fossa contour guide.
d. When the acrylic has set, the pin is raised and the guide removed.
7.

Because of the design of the special wax cutter pin. the lateral anterior

guidance angle will be evident as a sharp line running along the bottom edge of
the acrylic.

188

The ridges should be contoured to reflect food away from the contact which
means directing it into the fossae.
Porcelain occlusal veneers:
Porcelain veneers are much stronger if the veneer thickness is kept fairly
uniform. Waxing the teeth to contour first and then cutting the patterns back
about 1 to- 1.5mm. wherever porcelain is to be applied results in the strongest
possible porcelain application.
To make certain that the porcelain cusp tips are in the correct position, a simple
procedure can be followed that utilizes an easily made stone matrix. The
patterns are cast and prepared for porcelain application. With a marking pencil,
a mark is put in each indentation, which represents the exact tip of each buccal
cusp. The matrix is trimmed back on a model trimmer to the center of each
cusp tip mark. The matrix will fit back on the model, indexed to the front teeth,
and will serve as a series of reference points so the ceramist can build the
porcelain buccal cusp tips to the correct position.
The bottom edge of the guide is marked with a pencil and any excess acrylic
ground off in front of the line. One may actually hollow-grind the front surface
down to the line to make a scoop-shaped guide, which is excellent for shaving
out wax from the fossae.
There are just three basic rules for using ihc fossae contour guide(fig-64).
t. .Always hold the handle perpendicular
2. Never destroy a predetermined cusp lip
3. Locate fossae in proper relations to cusp tips
The front of the guide always faces front, and in that position it is correct for
either the right or the left side. When the handle is held perpendicular, it

189

exactly reproduces the lateral anterior guidance. Flattening the bottom of the
guide will provide extra room for a lateral side shift. F.ven though the side shift
is usually built into the anterior guidance (and consequently duplicated in the
fossae contour guide), it is a good practice to give a little extra lateral freedom
as insurance, especially since to do so takes away nothing that is needed in the
first place.
Modifications in using the fossae contour guide:
The fossae contour guide may be used before supplemental grooves are placed
or it can be used to refine fossae wall inclinations after all the occlusal carvings
have been completed. Carving the patterns with fairly deep grooves and
slightly convex inclines will usually require an opening out of the fossae, but
the result is an unusually natural looking occlusa! contour since it simulates
normal wear.
The fossae contour guide can be used in combination with dropped wax
techniques and gnathologic mountings.
Finished castings and porcelain occlusals can be checked by the dentist and
modified by selective grinding.

The fossae contour guide is an easy tool to

use. A quick analysis of each fossa can be made when the restorations are
received from the laboratory.
Carving the marginal ridges:
When all cusp tips have been properly located and the fossae correctly placed
and contoured, the marginal ridges seem to fall right into place.
The most common error noted in marginal ridge contouring is failure to evenly
line up the marginal ridges of contacting teeth would create considerable lateral
torque in the extremely stressful position near the condylar fulcrum.

190

More definitively, the anterior guidance contact should be maintained during ,
posterior contact in working excursions.
Balancing excursions:
The term "balancing excursion" is a remnant of full denture terminology. It
originally referred to actual balancing contact to stabilize the dentures on the
side of the downward moving, orbiting condyle. It is a part of the three-point
contact concept, which for denture stability is a good concept.
Bilaterally balanced occlusion docs not work because there is no way to
harmonize the "balancing" inclines of the teeth to all of the variations of muscle
force against the unbraced orbiting condyle. "Balancing" inclines must be
relieved on all restorations regardless of the method used to record the border
movements. The relief can be accomplished rather simply by slight hollow
grinding of the buccal inclines of the upper lingual cusps between the centric
contact in the fossae and on the tips of lingual cusps.
Since balancing incline interferences are so stressful, extra care should be taken
to make sure such inclines are never allowed to contact,
When applied to natural teeth, the term "balancing side" is obviously not a
correct connotation. Stuart and Thomas refer to the orbiting condyle side as the
"idling side". It is certainly a better term, since it correctly indicates a lack of
contact.
If the occlusion must be grossly adjusted on the finished restorations, one or
more of the following errors has probably been committed: Improper recording
of centric relation Errors in mounting Improper fit of finished restorations
Errors in cementation

191

FUNCTIONALLY

GENERATED

PATH

TECHNIQUES

FOR

RECORDING BORDER MOVEMENTS INTRAORALLY
In spite of its simplicity, the functionally generated path technique (FGP) can
be an extremely sophisticated method of capturing in a usable way the precise
border pathways that ihe lower posterior teeth follow. The technique has the
distinct advantage of being able 10 record all dimensions of such border
movements at the correct vertical as they are directly influenced by both
condylar guidances and anterior guidance.
Like any other technique for recording border pathways, the value of functional
path procedures is directly proportionate to the operator's understanding of
what he is trying to accomplish and why. When properly used, FGP procedures
are unsurpassed in accuracy and they require no compromise whatever in the
finishing of occlusal contours.
If the following facts are understood, the value of FGP as a logical method of
achieving precisely accurate occlusal contours will be obvious. 1.

Border

pathways of the lower posterior teeth are dictated by two different
determinants:
a. The anatomic limits of movement of the condyle - disc assemblies (posterior
determinant)
b. The anterior guidance (anterior determinant)
c,

Functionally generated path procedures, properly used on upper posterior

teeth. record directly all possible border pathways of the lower posterior teeth,
as they are influenced by both the anterior and posterior determinants. 3. The
shape of the occlusal surfaces of the lower posterior teeth has a profound
influence on the type of occlusion that is dictated by moving said shapes along
the border pathways through the functional wax.

192

Obviously, any dentist who does not wish to reproduce an incorrect existing
occlusion would not use FGP procedures until he has made certain that both ihe
anterior guidance and the lower occlusal contours are correct. However, if
either the anterior guidance or the lower occlusal contours are incorrect, there
is no technique that can produce correct upper posterior teeth.

193

RESTORING UPPER POSTERIOR TEETH
The upper posterior teeth should be the last segment to be restored. It is the
fixed posterior segment, and its cusps, inclines, grooves, and ridges are placed
and contoured to accommodate the many border movements of the lower
posterior teeth.
While it is possible to fabricate upper and lower posterior restorations together
on a fully adjustable instrument, upper posterior restorations should never be
fabricated against lower posterior teeth that require correction of their occlusal
plane cusp tip placement, or fossa contours. If it is absolutely necessary to
restore upper posterior teeth first, the lower teeth should be corrected as close
to optimum as possible with selective grinding or temporary restorations.
Preparing upper posterior teeth for occlusal restoration:
When upper posterior teeth are being prepared, they should be checked in all
excursions to make certain that there is room for a sufficient thickness of metal
or metal and porcelain.
Most important centric record:
Of all the interocclusal records that are made during occlusal reconstruction.
(he most important one of all is the one for articulating the upper posterior die
model.
Whenever possible, this final centric record should be taken at the correct
vertical dimension. Taking the centric record at the correct vertical dimension
eliminates any error thai would have been associated with a missed axis of
closure and provides the operator with a means of verifying the accuracy of the
centrically articulated models.

194

All of the occlusal inclines on the upper posterior teeth are related to the border
pathways that the lower posterior teeth follow. Whether it is desirable to have
excursive contact on certain inclines or a near miss, it will still be essential to
record the border pathways with extreme preciseness. Upper contours can only
be planned when we know exactly where the lower cusps will be traveling.
The effect of the border movements of the condyles must be recorded at least to
the extent that they can function within the envelope permitted by the anterior
guidance.
The important thing to remember about capturing border movements of the
lower teeth that determine upper occlusal contours.

Whether condylar and

anterior guidance determinants are captured directly to then reproduce tooth
movements on an instrument or whether the tooth movements are captured
directly at their site makes no difference, as long as the final upper tooth
inclines are in harmony with the functional pathways that the lower teeth
follow.
One of the most accurate methods of capturing border movements is the
functionally generated path technique.
The dentist must decide whether the upper occlusal inclines are to be in group
function, partial group function, or total disdusion in excursive movements.
Whichever decision is made, it is accomplished by contouring and angulations
of the inclines themselves. Supplemental grooves cut into inclines add to the
natural appearance and increase the gripping and shredding ability of the tooth
surfaces.
Logical approach to first develop the incline surfaces according to type of
function desired and hen carve into that surface the supplemental anatomy.
The grooves are carved smaller than the cusp tips. The tips will just pass over

195

the grooves with no effect on the actual contact through the excursive
movement.
Length of group function contact in working excursion:
If we elect to provide group function on the working side, we should be aware
that all teeth do no stay in excursive contact for the same length of stroke. As
the mandible starts its move to the working side, all the posterior teeth may
contact in harmony with the anterior guidance and of course the condyle. As
the mandible moves further to the side, the first teeth to dis-engage from
contact are the most posterior molars. The disengagement is progressive,
starting with the back molar, which has the shortest contact stroke, forward to
the cuspid, which has the longest contact(fig-65).
The reason for giving the cuspid such a long contact ride and a progressive
shorter contact as we go distally is based on factors of geometry and stress. As
the working condyle rotates, the path traveled around the center of rotation
lengthens as the distance from the condyle increases, While the cuspid is
traveling the full length of its incline from centric to its incisal edge, the second
molar is traveling about half that far. When the cuspid reaches its incisa! edge,
the molar still has some incline left on which it could ride out. However, if the
molar continued its contact after the cuspid was disengaged, the stress would
be no longer shared by the proiective anterior guidance. It would instead be
loaded entirely onto the outer incline of the molar and
Use of acrylic and other hard materials for fabricating the base: Any
material that can maintain accuracy through all the procedures is acceptable as
a base. It must not be flimsy, and it must be stable and retentive. Furthermore
the base must fit the master die model as accurately as it fits the mouth, and it
should not damage the dies when it is seated on and taken oft the master model.

196

Acrylic bases because of the distortion of the acrylic during or after setting and
the damaging effect of the acrylic on the dies.
Cross arch stabilization of the base: A common cause of error in FGP
techniques is hypermobility of the teeth. Cross-arch stabilization can be
affected by the base. Cast bases: When there are missing teeth, bases can be
cast in scrap gold or other metals. 'The functional wax table needs to be only
wide enough to represent the upper occlusal surface with a little extra to hold
the wax. Tables that arc too wide interfere with the cheeks.
The buccal and lingual edges of the cast table can be turned back to grip the
wax or holes can be drilled in the cast table.
Recording the border movements:
After all posterior contact is cleared, the following procedure is performed:
1.

The base is returned to the model and softened functional wax added for

recording the FGP. The functional wax is heated with a flame to make sure it is
quite soft and sticky enough to securely adhere to the base. It may be sealed to
the base with a hot spatula, but the base should not be softened too much or it
will distort. A common problem is using too much functional wax. We want
only enough to be impressed by about one third or less of each lower tooth. If
too much wax is used, the excess bulk is too easily moved by the cheeks and
tongue during the FGP recording and the path is useless.
Bosworths Synthetic Tacky Wax is an ideal functional wax because of its good
working qualities and ideal plasticity at mouth temperatures. A little of the
patient's saliva maybe picked up on the tip of the finger and applied to the
functional wax as a lubricant to prevent it from sticking to the lower teeth.
2. Using the same manipulative technique that was used for recording centric
relation, a closure is manipulated into the wax until the anterior teeth contact.

197

The patient should be told in advance to hold that position and then slide
forward until the anterior teeth are end to end.
Technique steps for bilaterally recording the fgp:
After the anterior guidance has been harmonized according to the patient's
functional, esthetic, and periodontal support requirements and after the lower
posterior occlusal contours (fossae contours in particular) have been
harmonized to the anterior guidance and the fossae have been freed for possible
side shift of the .mandible. The technique for recording the FGP is as follows:
Making the base for the FGP
1. Upper posterior teeth are prepared
2.

An impression is made of the upper prepared arch and, while the patient

waits it is poured immediately in hard stone. The impression material used for
this step should have a soft consistency so that it will not distort the soft tissues.
A smooth creamy mix of alginate is acceptable.
3. When the model has set, extra hard base plate wax is used to make a base
for the functional wax. The wax used for this step should be brittle hard so the
base will not bend without breaking. The wax is softened over a flame and
folded into three layers. While it is still soft, it is adapted around each tooth on
the model. It is pressed down very firmly over each tooth so that it will be thin
enough to see through on the occlusal portion. Then the wax is adapted down
around each tooth to completely cover all prepared teeth down 10 the gingival
margins.

The wax wafer should not be adapted to the palate.

It should go

straight across. It should cover only the posterior teeth but should be extended
right up to the unprepared cuspids(fig-66).
4. The chilled base is removed from the model and inserted in the mouth. This
base must be perfectly stable in the mouth. The base is seated firmly and

198

watched carefully for any spring back. If there is any movement whatever of
the base, the wax is trimmed back on the underside wherever it touches soft
tissue.
5. When it is certain that the base is stable, the patient should close his mouth.
There should be no tooth contact on the base. Contact in all excursions as well
as centric relation closure should* be checked. There must be no interferences
that will restrict the anterior guidance from functioning in its normal manner.
When there are fairly extensive edentulous areas (as an example) it may be
necessary to cast the base of metal. Regardless of what is required, the base
must fit the teeth and be absolutely stable.
3 The patient should close back inio centric relation and the mandible is guided
into lateral excursions. The dentist must guide the mandible through all
excursions to ensure capturing of all border movements. If the excursive
movements are left entirely to the patient, they will usually move in a protruded
lateral direction and the mandible will not move the lower posterior teeth as far
into the Bennett shift as it is really capable of doing in forceful movements. If
the condyles arc not forced to their outermost border positions during the
generation of the path in the wax. tooth interferences to the extreme border
positions will result in the restorations. These arc the same interferences that
usually go undetected by many dentists who do not use correct manipulative
techniques in equilibration. They are potent triggers for bruxism and are the
frequent cause of posterior looth hypermobility.
4. When all excursive movements have been recorded by manipulation of the
mandible, the patient should be allowed to slide around however he wishes.
This is the step that records the movements between straight lateral and straight
protrusive. If there are any interferences to any movement of the jaw. the

199

functional wax will simply be moved out of the way to record the outer limits
of all functional movements(fig-67).
5. The KGP should. be checked for any movement during excursions and to
make sure all pathways have been recorded in sufficient functional wax. If
everything appears to be in order, the wax is chilled with ice water to make it
quite firm. A creamy mix of stone is mixed by the assistant.

When the stone

is mixed, she should help hold the cheeks out again while the patient quickly
goes through one last set of excursions. The cheeks should be held out while a
creamy mix of stone is jiggled into all the depressions of the functional wax.
Vibrating the stone on the tip of the index linger while jiggling the mix ahead
of the fingertip works quite well. The fast-setting stone must cover at least one
unprepared tooth in front, and. if present, at least one distal to the prepared
ones.

The stone index over the unprepared tooth on each side will serve a

definite vertical stop and a positive key to the master dies when the functional
model is being used in the laboratory.
The stone will stiffen the entire base and protect the functional wax. It also will
make it easier to seat the FGP on the model without distorting the functional
wax(fig-68).
Application of the stone mix in the mouth has another important advantage. It
enables the dentist to check for any distortion that may have occurred during
the intraoral procedures.
Checking for distortion: When the FGP is removed from the mouth, it should
be placed back on the same model that was used to adapt the base. The stone
that covered over the unprepared tooth or teeth on each side should fit the same
teeth on the model without any distortion whatsoever, that is. no space should
be in evidence between the functional stone and the model stone, liven a slight

200

crack between the model and the FGP stone should not be accepted since it is
an indication thai the base has been distorted.
If the FGP stone, now called the stone core, fits perfectly against the
unprepared teeth in front and the wax base fits the model or unprepared teeth
perfectly in the back, we may assume that ihere has been no distortion of the
base.
A wax base should not be used when there are many missing teeth unless it can
be thick enough to ensure strength.
Laboratory Procedures:
Many technicians prefer 10 wax the patterns against the anatomic model in the
same manner they are used to. and then they refine the inclines against the
functional model. This is a logical procedure. However, the skilled technician
can soon "'read'" the functional model as effectively as the anatomic model.
Mounting the FGP:
1.

The opposing anatomic model is removed from the articulator and the FGP

base placed on [he mounted master die model. It should fit perfectly with no
rock. The functional stone core should fit against the cuspids (or an unprepared
tooth in front) without any crack showing. As long as the FGP base fits the first
model perfectly any discrepancies on the master die model can almost always
be resolved by removing soft tissue contact on either the model or the
underside of the base.
2. An inverted plastic cup with the bottom cut out makes a good form for
pouring the lower stone platform.

201

The stone core and the platform should be dampened and the two neatly joined
together with another mix. The guide pin should be set the same as it is for the
anatomic model.
There are a number of ways to check the accuracy of the FGP recording, and
fade accuracy checks are made at each step of the procedure from the intraoral
steps through the completion of the mounting.

None of the checks is

complicated or time consuming, but each is important: Using the functional
model:
The articulator is always locked in the position that allows absolutely no lateral
movement when the functional model is in use. The articulator simply serves as
a device to position the functional core in its proper relationship to the dies.
Since the pathways of the lower teeth are recorded three dimensionally in the
solid stone core, moving the articulator laterally produces an error. It must be
kept locked in centric relation position.
The technician has three options for using the functional model. He may:
1. Wax the restorations directly against the functional model.
2.

Wax against the anatomic model, then refine the occlusal inclines and

check for interferences against the functional model (stone core)
3. Complete the castings against the anatomic model, then adjust the metal or
porcelain occlusal surfaces against the functional model.
Making adjustments against the functional model:
When the restorations are in place on the upper die model, it should be possible
to close the articulator so that there is no crack between the "key" teeth and the
functional stone core. All restorations should be in contact with the functional

202

core. If there is any separation between these "key" teeth and the stone index, it
is an indication of an occlusal interference.
Group function is attained by adjusting the lingual inclines of the upper buccal
cusps to contact against the functional core (fig-69). Disclusion is attained by
taking the inclines out of contact with the functional core and leaving only the
selected centric stops in contact. The amount of space between the inclines and
the functional model will represent the exact amount of clearance between the
lower cusps and the upper inclines during excursions(fig-70). Balancing
inclines:
All excursions made during the recording of the FGP represent actual contact.
This includes balancing excursions. Since balancing side contact is undesirable.
balancing side disclusion must be effected by reducing balancing inclines on
the restorations so that they do not contact the functional stone at any point.
FGP checkbite technique:
The FGP technique can be used as outlined to check out castings that are
already complete, after the castings have been tried in. checked for accuracy of
fit. and then removed. To make sure the castings fit the mouth the same as they
fit the model, they should be tried in and a stone matrix made along the
occlusal surfaces. Fast setting stone is ideal for the matrix because of its rapid
setting time. The castings are then removed from the mouth and relumed to the
die model.
The stone matrix is trimmed back to the tip of the buccal cusps and placed on
the castings. The matrix should fit the castings on the model as perfectly as it
fit them in the mouth. Castings that have been checked in this manner and pass
the test can be adjusted against an FGP model with complete assurance of
accuracy,

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FGP for quadrant dentistry:
The real value of functional path procedures is more practically realized when
it is used bilaterally because of the stabilizing effect on the teeth and FGP base
when it is attached to both sides of the arch. Nevertheless funciional paths can
be recorded unilaterally if great care is exercised to assure the stability of the
base and if hypermobility of the teeth in the quadrant is not a problem.
A single quadrant may be prepared and FGP procedures may be used to
advantage if the base can be stabilized. In a unilateral quadrant ii is often
necessary to make a cast base in order to get enough stabilization.
When preparing a single quadrant, special care should be taken to make sure
the opposite side is perfectly equilibrated so that there are no deviating
interferences to influence the functional paths.
FGP for a single tooth:
One of the most common uses for functional path procedures is the restoration
of a single tooth. As a practical clinical approach, however, FGP for a single
tooth has minimal value. Using FGP for restoration of a single tooth involves
unnecessary extra procedures that require longer chair time, and in many
instances it produces unwanted results.
If there are occlusa! interferences present, the FGP will perpetuate them in the
restoration. If tooth inclines limit the movement, the FGP can be done directly
on the models.
The biggest shortcoming of single tooth FGP occurs in mouths with posterior
disclusion. Even it all other posterior inclines are discluded in working and
balancing excursions, restoring against a functional model will put the restored
inclines in full lateral contact.

204

If FGP is used in posterior disclusion cases, the restoration should be relieved
on the working and balancing inclines. If full arch hand-held models are used
instead of FGP. the disclusion of both working and balancing inclines will be
perfected right on the models, a decided advantage.
There is another potential disadvantage for single tooth FGP. If adjacent teeth
have any hypermobility they can move during generation of the path and the
path will be flatter in the wax than it is on the adjacent teeth.
If FGP is used, the tooth being restored must be stabilized during generation of
the path.
If full arch models are used, the position of the teeth stays the same as when the
impression was made. If the other occlusal inclines are correct in the mouth,
they will be correct on the models. Rubbing such models together with wax on
the die will produce the same inclines in the wax that exist on the adjacent
teeth, so thai the wax pat'.crn will also be correct.
Posterior inclines on each side of the die must be permitted to contact in order
to have their working and balancing inclines duplicated in the soft wax on the
die.
The Johnson-Oglesby Spring Arliculator is a practical device for holding full
arch models together while still permitting a full range of movement, including
contact of the balancing inclines on the model. The three essentials for a good
result are:
1. Occlusal correction before restoration
2.
3.

Full arch models
Reduction on the model of steep anterior inclines that prevent full

excursive contact against the posterior inclines being copied.

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Clinical procedure for single tooth FGP:
1. The occlusal reduction for the preparation is completed.
2.

Before doing any proximal reduction the tooth is stabilized with softened

slick compounded the same compound formed into a broader occlusal table to
receive the functional wax.
3.. The surface of the compound is roughened so that the functional wax will
not slide off.
4. Using a flame, the functional wax is softened (Bosworth's Synthetic Tacky
Wax is a favorite) and stuck to the prepared occlusal table.

The occlusal

portion is lubricated with saliva.
5. The patient should close into centric relation and move through all possible
excursions.
6. A creamy mix of Healey's Fast Setting Gray Rock of Whipmix Bite Stone
is made and vibrated into the FGP indentations. The stone is extended onto at
least one tooth on each side of the prepared tooth.
Note: FGP can be done on a terminal tooth if the base and the wax can be
made stable. On a terminal tooth, the fast-setting stone should be extended over
at least three teeth in front of the prepared tooth.
7. The hardened stone is removed and set aside. The compound and the wax
are removed and discarded, and the preparation is completed. An impression
of the prepared tooth is made, including all teeth that will be covered with the
stone functional core. An opposing model is not necessary.

206

Laboratory procedure:
1.

The impression with removable dies for the prepared tooth and each

adjacent tooth is poured. The functional core is positioned against the die
model. The unprepared teeth on the die model should fit perfectly into the stone
index.
3.

Any instrument that can repeatedly reposition the functional model with

accuracy is acceptable for mounting the two models. They can be mounted in
the joined position on a simple hinge aniculator, because the only requirement
of the instrument is to permit the models to be separated and then returned to
the same closed position. The arc of opening and closing has no importance,
and of course no lateral movement is permitted. All pathways are represented
on the functional model itself when it is closed. Instruments that have been
especially designed for relating the functional model to the die model include
the following.
a.

The verticulator (fig-71) is a device that permits only an up or down

movement. It is precision-made with a sturdy metal stop that permits the
functional model to be struck forcefully against the die model without danger
of model breakage. The verticulator is spring loaded so that with each closure it
springs open to give access to the die or pattern.
b. The twin stage occludcr is simple hinge articulator that will articulate both
a functional core and an anatomic model interchangeably against the same die
model(fig-72).
4. When using FGP for a single tooth, the pattern is generally waxed directly
against the functional core. The pattern should contact the functional model but
should not interfere with its closure. If the restoration is to be in group function,
the lingual inclines of the upper buccal cusps should be in continuous contact
with the functional model. If the inclines are to be discluded. they must be

207

reduced so that there is no contact, but centric relation contacts must not be
tost. In all cases, the balancing inclines should be relived from any contact with
the functional core.
FGP for lower teeth:
Functional path procedures are not generally used on lower teeth. For KGP to
work on the lower teeth, the upper inclines would have to be perfected first. If
the lover tooth is not in contact, it can be built up with compound or a wellmade temporary restoration and the occlusion refined prior to taking the
functional record. This is referred to as cup-fossae analysis.
Cusp-fossae analysis can be accomplished very effectively on the stone
models. It is safer to adjust the occlusion against the finished restoration than to
take the chance of wiping away the lower buccal cusp in FGP wax against
upper inclines that may be in interference.
FGP can be used on lower teeth, but only if the upper occlusal contours have
been perfected first. This is true for a single tooth or for multiple teeth. For
multiple teeth there is the added problem of stabilizing of lower base against
tongue and cheek action. It usually must be a cast base. In lower teeth the
dentist is not interested in having any inclines in function, only functioning
contacts on the buccal cusp tips and centric contact in the base of fossae. This
can be accomplished in more practical
Ways that using
Using FGP for cross bites Posterior cross bites can be restored using FGP if
lower cusp tip placement and cast fossae contours have been perfected in
advance.

In all cases, the balancing inclines must be additionally reduced

when FGP is used.

208

PROCEDURAL STEP IN RESTORING OCCLUSION
Restoring posterior teeth before the anterior guidance is

finalized

is an

example of a common error of sequence.
Two of the best rules to follow for staying out of trouble with restorative
procedures are: 1. Sever begin any restorative procedure unless all the
procedures that follow are outlined in advance and properly related to one
another in correct sequence. 2. Never begin any restorative procedure unless
the end result is perfectly visualized and understood.
Preliminary mouth preparation:
1.

Mouth hygiene instructions should be given

2.

Caries control should be achieved

3.

Periodomal therapy should be completed.

J. Minor tooth movement should be complete. Stabilization of the occlusion
following any orthodontic procedures should have occurred. When teeth have
been moved ample lime should be given for reorganization of the periodontal
fibers and bony support before final impressions are made for restorations.
5 Necessary extractions should be done and tissues healed before permanent
placement of fixed prostheses.
6. Equilibration should be completed prior to preparation of the teeth. The
temporomandibular joints should be comfortable prior to finalizing any
restorative treatment.

209

Sequential steps for restoring different combinations:
Following is a general list of the variations in restorative needs of different
patients. A suggested sequence of restorative procedures is outlined for each
type of case. The outline is general and it may be necessary to vary the
procedures or the sequence for particular needs of certain patients.

210

RESTORING ALL UPPER POSTERIOR TEETH ONLY
RESTORING ALL UPPER TEETH BUT NO LOWER TEETH
RESTORING ALL POSTERIOR TEETH BUT NO ANTERIOR TEETH
RESTORING ALL UPPER AND LOWER TEETH
PREPARING ALL UPPER TEETH AND LOWER POSTERIOR TEETH
ONLY

211

REVIEW OF LITERATURE
HINGE AXIS
Campion(1902,1905) produced probably the first graphic record of mandibular
movements on a patient, he used a basic form of pantograph which produced a
succession of dots on the skin of the side of the face as the condyles moved
during function, the slope of the condyle path in different individuals was
demonstrated by comparison with an imaginary line from the external auditory
meatus to the lower border of the nose, from his work he concluded ' ... there is
and can be no one axis about which the mandible moves in opening the mouth,
but that the movement is a complex one. consisting first of a rotation of the
bone on an axis passing approximately through the centers of the two condyles,
and secondly of a forward and downward movement of the condyles as they
slide over or with the meniscus-shaped inter articular cartilage along the curve
of the eminentia articuiaris".
Bennett (1908) in his classical paper on movements of the mandible, stated
that no single fixed center of rotation for the mandible existed since the center
of rotation constantly shifted (for movements in the sagittal plane). However,
he did point out that the mandible was capable of two independent movements;
one. an angular rotation about the condyle, the other a translation movement
produced by the gliding of the condyle along its path. Using geometrical and
mechanical theories, based on work carried out on himself when undertaking
mandibular movements, he demonstrated the instantaneous centre about which
the mandible was at any moment turning, for every position of the mandible.
He accepted the criticism that the experiments were carried out on one
individual (himself) as that no general conclusions could be drawn from them.
Gysi(19lO) presented a treatise on the history of articulators and described
instruments used for determining the slope of the condyle path. He stated that

212

the natural condyles could not b£ considered as true rotation points or axes
above which the various movements of the mandible occurred, but should be
regarded only as fixed guides of the mandible in its movements. He stated ',.,
The mandible in opening and closing rotates around anther center, which,
however has no influence in the setting up of the teeth for articulations, and
therefore need not be considered in the construction of an articulator.

Needles (1923) carried out experiments to test the accuracy of articulators and
came to the same conclusion as Bennett, viz. there were two fundamental joints
between the mandible and the maxilla. One was a hinge joint with the axis
through the heads of the condyles; the other was a sliding joint between the
fibrocartilage and the articular eminence. He said that any movement of which
the mandible was capable was the result of the movement in one or both of
these joints.
In a further paper (Needles 1927) he again discussed the two parts of the
temporomandibular joint. He though the only logical method of studying
mandibular movements was to divide them into their two elementary
components and refer each movement to its respective part of the joint. With
regard to articulators he said that, with any type, the axis of the opening
movement should be so placed as to correspond lo the heads of the condyles.
The articulator could then be opened or closed a considerable distance without
producing any error is the occlusion of dentures or prosthetic appliances.
Bennett (1924) discussed mandibular movements in relaiion to prosthetic
dentistry and again stated that there was no center of rotation in the
temporomandibular joint itself. Movements of the mandible in the sagittal
plane were composed of rotation about the line of the condyles and translation

213

in the direction of the condyie paths giving instantaneous or constantly shifting
centers.
VVadsworth (1925) referred to the anatomists conclusions. He stated that the
first movement of the mandible occurred around a transverse axis passing
through the condyles. the condyles themselves remaining sealed in the fossae.
The second movement was a sliding movement, the condyles gliding forward
onto the articular eminence.
Stansbery (1928) was^dubious about the value of face bows and adjustable
articulators. He thought that since an opening movement about the hinge axis
took the teeth out of contact, the use of these instruments was ineffective
except for the arrangement of the teeth in centric occlusion. In his opinion, the
plain line hinge type of articulator was jus as effective.
Hall (1929) reviewed early work on articulators and the investigation of
mandibular movements. He credited Balkwill with describing practically all the
movements of the mandible then known. He quoted Balkwill, who had stated in
1866. A side view shows that the condyle articulates with the glenoid cavity so
as to allow of a simple hinge like motion, and a forward and backward motion.
When the teeth are shut, the condyle lies at the back of the glenoid cavity,
where, the front of the lower jaw being depressed, it turns like a hinge. The
work of lace was also reviewed by Hall. He had concluded, as a result of his
(Luce's) investigations, that the condyle advanced even if an effort was made to
it back. Hall stated: "It is noted that the question of whether or not the condyle
is the centre of the opening movement in slight movement was a point of
contention in Luce's time, just as it is today. I believe, as Luce did, that it is
not".

214

McLean (1937) stated:
The hinge functions of the lower portion (of the temporomandibular joint) are
still disputed and little understood. The hinge portion of the jaw has two
functions of great importance to Prosthodontists.
First, the hinge portion of the joint is the great equalizer for disharmonies
between the gnathodynamic factors of occlusion... When occlusions are
synthesized on articulators without accurate hinge axis orieniation. there may
be minor cuspal conflicts, which must be removed by selective spot grinding.
Regarding the satisfactory construction of full dentures, he said that opening or
closing the bite on an articulator with an incorrect hinge-axis location would
result in unsatisfactory occlusion of the dentures when they were placed in the
mouth. When the hinge axis on the articulator was too far forward compared
with a location on a patient, closing the interocclusal distance would result in
the dentures meeting prematurely posteriorly.

If the axis was too far

posteriorly, premature contact would occur anteriorly. If the axis was too low,
the lower denture would be forward of centric relation. If too high, the lower
denture would be posterior to centric relation. The conclusion was that any
alteration in the interocclusal distance must either be made in the mouth or by
the use of a hinge-axis articulator. If the latter were to be used, then the hinge
axis must be determined as a stationary point (i.e. rotatory but not translatory)
over the head of the condyle during hinge-axis movements and not by palpation
or anatomical location.
McCollum (1939) published a very important series of articles concerning
restorative remedies. Since he was one of the leading advocates of the "hingeaxis theory", it is important to quote a large part of his work:
Prominent anatomists have insisted that there is no true hinge joint in the body
only because they have understood the mechanistns of a hinge. Some

215

anatomists seem to believe that a hinge-action is a total movement between an
edge and a surface such that the axis of rotation lies on the surface. They are
confusing pivotal action with hinge action and do not realize that door hinges
work by one surface gliding over another, the amount of gliding depending on
the size of the pin, but the centre of action is an imaginary axis through the
centre of the pin.
In 1921, I became convinced that the opening and closing centre of the
mandible was a most important factory in dental articulation and that it
determination was preliminary to the transferring to an articulating instrument a
record of jaw relations. Snow and others, in a gross way, had recognized an
importance and thirty years previously had invented the face bow and a method
for its use. Gysi definitely recognized the importance of the opening and
closing axis to articulation, as is evidenced by the statement that the raising or
lowering of the bite is a chair operations. Bui he failed to grasp the necessity
for its being recorded in instruments as accurately as he tried to record the
other phases of jaw motions. His experiments wore so inaccurate that he
concluded that a hinge-axis, if it did case was down below the condyles near
the lower border of the tragus and he actually made an articular accordingly.
However, his latest articulators has the hinge axis in the condylar region, but so
far as know he does not ascribe much importance to it; changing vertical
dimensions with him is still a chair operation... Now it must be obvious to the
siudious that, if the articulator absolutely duplicates as jaw relation, it is
possible to alter the vertical dimension by either raising or lowering the bite on
ihe articulator and have the same conditions prevail in the mouth as existed on
the instruments.
McCollum described how; he came to demonstrate conclusively the existed of
a definite opening and closing axis by using a face-bow rigidly attached to the
lower teeth with orthodontic appliances. The development of accurate and rips

216

clutches, and adjustable face bows, led to the determination of the hinge axis
easily. He also demonstrated, by means of diagrams showing exact locations
nine pairs of hinge axis points that external landmarks were of little use
location of the axis.

In addition to wide variation in anatomical location of

these points, he also found great variation between sides on the same
individual. He gained the impression, however, hinge axis point remained
constant in the tattoo dot on the skin throughout life.
Further work on cadavers showed that the hinge axis bore no Constance's
relationship to ouiside landmarks and that the only satisfactory method of
locating the axis was by trial and error. Although it was necessary to open the
jaw slightly to avoid cuspal interference when determining the hinge axis, he
was quite satisfied that the mouth could be opened by as much as one half inch
in the incisor region in every individual, and in some individuals by as much as
one inch without the condyle heads moving forward in the fossae.
Stuart (1939) complemented the work of McCollum in his discussions on the
articulation of human teeth, the relationship of the mandible to the maxilla, and
the cuspal interdigitation of the teeth. These two workers were the pioneers of
'gnathology' as it is practiced today. Their early work led to the publication of a
research report (McCollum and Stuart 1955). which formed the basis of the
postgraduate teaching in the subject.
Higley (1940) discussed controversies surrounding the temporomandibular
joint including the manner of its development, adaptive changes in the joint, the
importance of the joint to articulation, muscles controlling mandibular
movement, and movement patterns of the mandible and condyle. Referring to
McCoHum's work, he stated; No matter what may finally be proved regarding
these movements of the condyle it would seem that the Gnathological Society
(of Lee Angeles, headed by McCollum) has developed an excellent technique

217

and one that will always be of value, because, clinically it has seemed
adequate.
In an attempt to clarify the contradictory statements regarding movements of
the mandible, and particularly the question of whether it was possible for the
condyle to exhibit hinge action only, and retain its centric relationship, Higley
Logan (1941) analysed condyle action as shown by radiographic examination.
The results showed that, in all the subjects studied, as the mandible dropped
from occlusion to an opening of 15 mm, there was a rctrusive movement of the
chin point, and the head of the condyle dropped progressively. The majority of
the subjects (70.6%) showed a forward shift of the head of the condyle from
occlusion to physiological rest position.
With an opening of I Omm. 95% of case showed a forward shift of the head of
the condyle. When the mandible was opened 15 mm all the subjects showed a
forward movement of the condyle.
McCollum (1943) reiterated his ideas concerning the hinge axis concept. He
said that in simple opening movements (if the mandible, the joint acted as a
common axis. This action took place anatomically by rotation of the head of
the condyle in the lower surface of the meniscus. It was possible for the
mandible to the simple opening to the extent of separating the incisors from
half an inch with individuals, lo 1.5 inches with some individuals. He though
that one of the confusing ideas about this opening component was that it could
accompanied by a contraction of the external pterygoid muscles which pulled
the condyles and menisci forward in the temporomandibular fossae. The
combined action was a natural elements of the chewing motions, especially the
prehensile or biting capsule. Therefore, when the individuals were told lo open
his mouth he would automatically combine these movements. He pointed out
that in order lo determine the true opening component it was necessary lo
ensure the individuals did not combine these movements.

218

McLean (1914) said that the diagnosis of "pathological occlusion" dependent
on the fact that the final phase of jaw closure was a pure hinge movement.
This movement, he said, required rehearsal or guidance from the hand of the
operator of the chin.
Branstad (1950) dealt with the problem of function in periodontal disease and
though! most of the emphasis in the treatment of traumatogenic occlusions or
to articulation had been placed on selective grinding performed directly in the
mouth. This, according to some authorities, merely moved the disease from one
both to another. This led him to think, therefore, that a description of the
biological factors, which should be understood in order to create and maintain a
physiological articulation, was called for. He said thai the only practical way to
diagnose what type of corrections or restorations were necessary to enable the
south lo function physiological, was to record maxillomandihular relationships
as an instrument capable of reproducing mandibular movements. In his
opinion, as adjustable articulator was as important in oral diagnosis as a
microscope was in pathological or bacteriological
In a further paper (Sloane 1952) he staled; "One component of mandibular
function, the mandibular axis, is of pre-eminent importance. The mandibular
arc is not a theoretical assumption, but a definitely demonstrable
biomechanica! fact. It is the axis upon which the mandible rotates in an
opening and closing function when comfortably, not forcibly, retruded. He said
that if the mandibular axis as recorded . and transferred to an anatomical
articulator the casts could be mounted so thai they opened and closed on the
articulator in the same fashion as patient's jaws. A method of locating the
mandibular axis and transferring it to modified llanau instrument was
described.
Clapp(1952) was in agreement with Gysi's (1910) ideas concerning
mandibular movement. He considered that there were a number of axes for

219

opening movements of the mandible and that they were all located outside the
mandible except the one for extreme opening. The infrahyoid muscles were the
activators of the straight opening movement rather than the external pterygoid
muscles. This article was published at a time when the hinge-axis theory had
been accepted by a number of authorities following the work of McCollum
(1939. 1943) as Granger (1952). It is interesting to note that Clapp was the
first American pupil of Gysi at Zurich in 1912.
Granger (1952) pointed out that each lemporomandibular joint consisted of
two joints. The one between condyle and meniscus was a pure ball and socket
joini capable of rotational movements in a vertical and horizontal plane. The
ball and socket could function in this way while the joint itself was gliding
bodily in the glenoid fossa. In use. gliding and rotation usually occurred
together, and this together with bodily movement of the mandible, gave rise to
complex mandibular movements. Granger stated that all rotations responsible
for mandibular movements had axes. which met at a common point within each
condyle. If these two points were joined by an imaginary line this would give
the transverse hinge axis. He said that the hinge axis was constant to the
mandible since gliding movement did not alter the relationship between
condyle and meniscus but ihc relationship of the hinge axis to the glenoid
fossa. There was only one position where the hinge axis was common to both
mandible and maxilla and that was centric relation.
Craddock and Symmons (1952) stated that in normal subjects, and for small
opening movements, the horizontal axis of rotation did pass through the
condyles and that in wider opening movements the axis became progressively
displaced downwards. They considered that the accurate determination of the
hinge axis was only of academic interest since it would never be found to be
more than a few millimeters distant from the assumed centre in the condyle
itself. The assumed centre could be found by palpation or by measurements one

220

centimeter anteriorly along a line drawn from the upper free margin of the
tragus of the ear to the corner of the eye. They concluded that a difference of a
few millimeters in the location of an axis which is about 100mm distant from
the point being observed could have little influence on the axis generated.
Posselt (1952) in his extensive studies, was concerned with the problem of
whether hinge opening around an inter condylar axis was typical of habitual
opening. He thought that hinge opening was better performed as a passive
movement, or as an active movement after suitable training. However, he could
find nothing to support ihe view that this type of movement was performed as a
habitual movement. Posselt's registrations showed the possibility of performing
a posterior hinge opening of the mandible during a posterior opening
movement of a certain extent and this he confirmed by postmortem registration.
He presumed this took place

in the lower compartment of the

temporomandibular joints. The extent of the hinge opening betw cen the upper
and lower incisor teeth was found to be i 9.2 mm + 1.9 mm, although he said
this was not necessarily the maximum.
Page (1952) described the hinge bow, developed by McCollum in 1936. and
said... it was one of the most important contributions made to dental science.
He pointed out that although the hinge axis was entirely theoretical, the jaw
must revolve upon such an axis since it could carry out rotary movements.
Lucia (1953) stated that movements of the mandible was accomplished by a
simple rotation of the condyles on the lower surfaces of the menisci and that
this hinge motion could take place at any point along the condyle path as the
menisci moved along the glenoid fossa. He questioned the practical application
of the hinge action of the joint and whether it was possible to locate this centre
in a practical way. In answer he said: "The practical importance of the hinge
axis and hinge axis transfer

221

of casts to an articulator is of tremendous importance. Without a hinge axis
transfer he thought it is impossible lo diagnose an occlusal problem because the
teeth on the models would not meet in the same way as they would in the
mouth, a centric relation record could not be verified, an articulator could not
be produced which would have the cusps meeting in the same are of closure as
thai of the patient.
Brandrup-Wognsen (1953) discussed the theory and history of face bows. He
quoted the work of Beyron who had demonstrated that the axis of movement of
the mandible did not always pass through the centers of the condyles. Although
the mandible did not always pass through the centers of the condyles. Although
they rarely coincided they were always close to each other and BrandrupWognsen concluded that complicated forms of registration were rarely
necessary for practical work.
Granger (1954) gave an account of the hinge axis and mandibular movements.
He stated thai the mandible was capable of an infinite variety of paths of
movement; one condyle could be undergoing only rotational movement while
the other condyle was both rotating and gliding, or both condyles could be
undergoing both rotational and gliding movements simultaneously.
In conclusion. Granger stated thai successful treatment depended upon the
correct orientation of the teeth to each other and to the hinge axis. Functional
movements of the mandible started and ended at centric relation (terminal
hinge relation). Correct orientation of the teeth in centric occlusion, therefore
dependent upon the correct relationship of the teeth to the hinge axis recorded
with the teeth orientated to each other in the most retruded position of the
mandible.
Sicher (1954) thought that some of the misunderstandings about mandibular
posilions and movements were due to problems of terminology, and he opened

222

his paper with a number of definitions of which that concerning the hinge axis
is quoted: Hinge, or terminal hinge, position is the position of the mandible
from which the mandibular hinge axis is determined or registered. It is the most
retruded position of the mandible that the individual can assume under the
action of his mandibular musculature and is. therefore, an unstrained position.
He slated that every person could move the lower jaw in hinge movement to an
opening of O.5-O.7S of an inch, or even more, bul what he wanted to know
was whether his movement was unnatural, forced, or learned. He concluded
that the hinge position was the most retruded position of the mandible achieved
by the action of a patient's own musculature.
Thompson (1954) was concerned with full mouth reconstruction ofthe natural
dentition. He described his modification of a face-bow so that accurate hinge
axis location could take place. This enabled him to mount the models of a
patient on an articulator so that the same relationship which existed between
the dental arches and the hinge axis ofthe patient was recreated on the
articulator.
Page (1955) criticized the report ofthe official Nomenclature Committee
Meeting of 1952 for its definition and explanation of hinge opening position.
He said that it was a misconception and had failed to recognize that none ofthe
groups who used kinematic location ofthe hinge axis considered this a
significant component of mandibular opening. These groups stressed thai the
important mandibular movement to be recorded was functional hinge closing.
Page also stated that the jaw did not rotate open to rest position on the hinge
axis, but that the whole jaw relaxed with the condylcs dropping into the
hammock and capsular ligaments. This view differed somewhat from that of
Eberle (! 951).
Colled (1955) stated; "There is not agreement on ihe existence ofthe hinge axis.
It is importanl to those who believe in its existence, because by using it we can

223

record centric relation at a level above the place where the proprioceptive
reflex occurs, transfer our recording to an articulating instruments, and on the
instrument, close down to the occlusal level. Hw said that the recording ofthe
opening axis and the transference of it to an articulator were of considerable
value in the diagnosis and treatment of occlusal malfunction.
Korn field (1955) discuSsed the anatomy of the temporomandibular joints and
outlines the technique of recording the hinge axis and its transfer to the
articulator. He stated that the location ofthe hinge axis was the basis of all
articulator transfers. and made the study and treatment of masticator disease
easier and more intelligible. If hi models of the mouth were not mounted on the
hinge axis, then restorations would not meet correctly in the moulh. a centric
relation record could not be verified, an articulator could not be adjusted to
reproduce jaw movements accurately, an occlusion could not be formed with
cusps which were in harmony with the arc of closure of the mandible, and any
changes in vertical dimension would produce occlusal disharmonies. He
concluded that most problems encountered with restorations could be traced to
the failure to maintain a correct relationship to the hinge axis. The importance
placed upon centric relation by Granger was also echoed by Korn field when he
said that the only position at which it was possible to locate and reproduce the
hinge axis was at centric relation, and that centric relation was only one
position of the hinge axis.
Lcvao (1955) staled, as have many workers previously, that mandibular
movements were a combination of rotation and / or translation in either or both
condyles. He described how hinge axis records were obtained on both cadaver
and patients, but said; there is a possibility that the hinge axis does exist, but is
may not be necessarily located within the condyles. Depression of the mandible
is a hinge like opening may cause the condyle to traverse a radial arc. Of its
own. due to the influence of the external pterygoid musculature.

224

Although the interference drawn appeared to negate the value of hinge axis
recordings, he assumed that it was possible to demonstrate a valid hinge axis
passing though or near both condyles. Levao's (1955) article was an important
contribution to the literature, as many of the statements had not previously been
nonarcon type articulators. Levao pointed out the nonacron type articulators
were unsatisfactory for reproducing eccentric pathways when their use was
based on hinge axis transfer since. with these types, the condylar axis moved
backwards. This increased the condylo-incisal distance and consequently a
change in he radius of the rare of closure took place with such movements.
Trapozzano(l955) gave an excellent dissertation on the subject of occlusion
including many clear definitions. He said that the presence of a terminal hinge
axis and centre of rotation from occlusal position through, and in may instances
greatly beyond, the next positional level, had been demonstrated repeatedly.
The fact that the registration of the hinge axis involved a learned movement he
thought in no way invalidated its accuracy or usefulness. He said it was
precisely because the hinge axis represented a "border" position that it was
capable of being recorded repeatedly with unfailing accuracy.
Beck and described the Bcrgstrom arcon articulator and pointed out, as Levao
(1955) had done, that with a non-arcon articulator the beginning and end points
were the same as the beginning and end points of mandibular movements.
However, only the arcon-type of articulator would reproduce mandibular
movements accurately between these two points. He stated that a constant
relationship existed between the occlusal plane on the arcon guides of the
instrument at any position of the upper member, making the reproduction of
mandibular movements more accurate. One interesting factor which the authors
discussed, and which has always been recognized but seldom mentioned, was
that there is a possibility of incorporating multiple errors into articulators of
complex design because of the increased number of measurements and

225

adjustments. The total of these errors may exceed the errors introduced by
assigning fixed values to some adjustments.
Cohen (1956) carried oul experiments on a patient using a Gnathoscope and
Gnathoyraph and found that, within the ranye of opening of the vertical
dimension used, there was conclusive evidence for Morrison (1956) the
existence of a hinge action of the mandible.
Nevakari (1956) investigated the nature of mandibular movement from rest
position to occlusal position using ccphalometrics. He found it impossible to
determine whether the movement actually occurred around a stationary axis or
whether it was composed of rotatory and translatory movement taking place at
different times.
Schallhorn (1957) discussed the advantages and disadvantages of an arbitrary
hinge axis location for face bow Transfer compared with kinematic locations.
Experiments were undertaken to compare kinematic hinge axis location with an
arbitrary location 13 m anterior to the tragus on a line from the tragus to the
outer canthus of the eye.

In over 95% of subjects with normal jaw

relationships the kinetic centre was found to be within a radius of 5mm from
the arbitrary centre. Schallhorn said this was within the limits of negligible
error.
Woelfel, Hickey and Rinear (1957) demonstrated electromyographcially that
hinge opening could be accomplished when a trained subject made this type of
opening, since no increase of electrical activity was recorded from the normally
functioning external pterygoid muscles. The results indicated that the
ncuromuscular system was so arranged that hinge movement of the mandible
was possible. This did not, however, preclude the possibility of the bony
structures of the temporomandibular joints interfering with a true hinge
movement. When the bony struciure of the temporomandibular joint and shape

226

of the meniscus would permit, the neuromuscular system was such that a
significant amount of hinge movement could be accomplished. However, they
said that for most individuals this was not a normal opening pattern.
So far little discussion has taken place regarding the split hinge axis theory. A
type of articulator called a Transograph was developed in an attempt to
overcome the problem of irregular condyles. which made it impossible for the
various individual axes (including the transverse hinge axis) to be constant,
even in simple rotation. This instrument made use of a transverse split hinge
axis. Trapozzano (1957) disagreed with the theory and practical aspects of this
technique and stated thai to have two separate axes, or a split axis, then the
mandible would have to bend or the continuity of the mandible would have to
be broken.
Posselt (1957) carried out the following experiments
1. Geometric constructions from a profile radiographs
2. Axis points recorded by a kinematic face bow and checked by profile
radiographs;
3. Hinge axis established by a kinematic face bow and verified by
gnathothesiometric methods.
His results showed that the axis of terminal hinge movement passed through
both condyles. and made only minor shifts, for openings of 15-2Omm.
In further studies to demonstrate mandibular movements Posselt (1958)
showed that the envelope of sagittal movement he said was pure hinge
movement around an inter condylar axis. He also stated that extreme opening
movements differed from habitual opening and closing movemenis and this
could be seen clearly in his diagram of the envelope of sagittal rotation of the
mandible.

227

Borgh and Posscli (1958) reported on their experiments relating to the hinge
a\is of the mandible using a Hanau model H articulator. They concluded that a
hinge movement could not be recorded accurately without error, although there
was some doubt about the accuracy of the machining of this articulator. The
findings on the -whole confirmed those of Kurth and Feinstein (1951).
In determinations of the hinge axis, clutches are used, attached to the upper and
lower teeth (or to the ridges in edentulous cases.) Sheppard (1958) undertook.
experiments to see what effect the presence of clutches in the mouth had on the
position of the condyles, using radiographs for comparison. He found the
clutches immediately altered the closed position of the condyles in most of the
joints studied and could also limit the extent of condylar movement. These
effects obviously have an important influence on the accuracy of such a precise
technique as hinge axis location.
Page (1958) stated that there were at least twelve hinge axes in every head,
three in each temporomandibular joint and three in each mandibular angle.
These, he said, were responsible for movements in all three planes.
Beck (1959) carried out experiments to compare the relative positions of the
following axes of rotation.
1. Bergstrom's axis. This was an arbitrary axis located automatically by his
face bow !0mm anteriorly to the centre of a spherical insert for the external
auditory meatus, and 7 mm below the Frankfurt plane.
2. Gysi's arbitrary axis. This was on a line from the upper margin of the
external auditory mealus to the outer canthus of the eye. 13mm in front of ihe
anterior margin of the meatus.

228

3. Beyron's arbitrary axis. This was located 13mm anteriorly to the posterior
margin of the iragus on a similar line to Gysi's. i.e. along the line from the
tragus to the outer canthus of Ihe eye.
4. Kinematic axis. This was determined using the method developed by
McCollum.
The kinematic centre of rotation for each of twelve subjects was found in the
accepted way using clutches and then the other axes were determined by
measurement. Small metal balls were placed over each axis point and
radiographs taken so that the relative positions could be seen and compared.
The Bergstrom points compared most favorably with the kinematic points, the
majority lying within a radius of 5mm. Beyron's axis points compared well
with the kinematic points, while the Gysi points showed a greater difference
from the kinematic points.
The existence of a fixed axis of rotation for the mandible was questioned by
Beck who postulated that it was impossible to determine with the face bow
alone whether the linear displacement of the condyle point tip was due to
rotation alone and due to rotation and translation. He used a modified Hanau
articulator to demonstrate how it was possible to locate a seemingly stationary
point when translation as well as rotation occurred. In conclusion he felt that
the selection of an arbitrar\ axis was justified.
A review of the literature concerning the hinge axis would not be complete
unless the work of Weinberg was discussed. Since Weinberg is one of the
leading authorities on this subject, adequate space must be given to summarize
his investigations and findings. Weinberg (1959) attempted to clear up any
misunderstanding concerning the hinge axis in the following way. He
1.

Described the hinge axis

229

2.

Described geometrical and clinical methods for finding it:

3.

Described its use;

4.

Determined whether there were one or two transverse hinge axes:

5.

Discussed the mandibular movement pattern for the opening and closing

movement
6.
7.

Gave clinical evidence of the transverse hinge axis
Determined if pin point accuracy in the location of the transverse hinge

axis was necessary and
8-

Related these factors to clinical practice.

Further reports by Weinberg (I960, 1961) were concerned with articulators and
face bows and reinforced the above findings. One important factor which was
not stated, but was obvious, in the earlier work was that marked deviation of
the hinge axis resulting from arbitrary location could cause marked anteroposterior mandibular displacement, even with small changes in vertical
dimension.
A series of article by Weinberg (1963) evaluated several articulalors and their
basic concepts. These arc now recogniz.ed as some of the most important
dissertations on articulator design. It is worthwhile repeating Weinberg's
findings especially concerning the hinge axis. He stated that the transverse
hinge axis passed through both condyles and was associated with rotation of
the mandible in the vertical (sagittal) plane. It was of clinical importance for
orientation of the maxillary cast on the aniculator and the subsequent accurate
transfer of the centric relation record, With regard to recon and non-arcon
articuiators. he disagreed with Levao (1955), and Beet and Morrison (1956)
and stated that both instruments produced the same movement because

230

condylar guidance was the result of interaction of a condyle ball on an inclined
plane. Reversal of the relationship would not affect the guidance produced.
Shanahan and Leff (1959,1962) published an important series of reports on
their studies of mandibular and artieulator movements. Initially, they recorded
opening and closing movements, graphically, on a hinge axis artieulator by
attaching a pencil to the incisal guide post. Photographs were then taken using
pin point illumination in a darkened room. These results wee compared with
photographs taken of a subject making similar movements.

They concluded

that the normal opening and closing mo\ements of the mandible did not
coincide with tne opening and closing movements of an artieulator. Shanahan
and Lcff (1959. 1962) stated that the There is w wciv>re3d belief that the
mandible opens and closes on an axis and that the mandibular teeih open and
close into centric occlusion on arcs with centers of rotsLkwi in the region of the
condyles. "Their later studies of tracing of natural opening, closing, and
masticating movements of the mandible did not show the presence of a
mandibular axis in the region of the condyles. but they did say that an artificial
mandibular axis could be produced during opening and closing movements by
forcing the chin backward. However, this was not a normal physiological
movement.
Brotman (I960) was of the opinion ihat the hinge axis theory was surrounded
by groups of research workers with strongly differing views. He attempted to
clarify the subject b\ discussing the clinical and geometrical significance of it.
He stated that
'The hinge axis position of the mandible is the most retruded position of the
mandible from which opening and closing movement can be made. When a
mandible is opened and closed in hinge axis position, it is possible to locate a
centre of rotation - the transverse hinge axis. He went on to question whether
the hinge axis position was the correct maxillomandibular relationship, but

231

since fixed occlusal restorations made to this position had functioned
satisfactorily he concluded it was a physiologically acceptable position.
In a further paper (Brotman 1960) he showed mathematically that if the hinge
axis interocclusal records were made at relatively small degree of opening (not
more than 5mm) and if the maxillary model was not far from its correct
position relative to the hinge axis (not more than 5mm), the maximum error
introduced by closing the articulator to occlusal contact would be the number
of mm of articulator close (from the vertical dimension at which the lower
model was mounted) multiplied by the error in the hinge axis location (in mm)
and divided by 100. He concluded that there was no simple way to determine if
the maxillary model had been improperly related to the hinge axis of the
articulator. The only way to avoid or reduce errors was to use a hinge bow, a
suitable articulator. and a precise technique.
Further work by Lucia (1960) supported opinion held previously. He said that
although he jaw could open and close in a hinge manner, it was not a normal
movement, but one that patients could be taught. The centre of this movement
could then b reproduced on the articulator. Lateral movements of the mandible,
he also stated, had centers in the condyles on the hinge axis. When these
centers were located on an articulator. all the patients' mandibular movements
could be very easily duplicated. The method of findings these rotation centers
was described.
Cohen (1960) described an instrument he had devised to train patients to open
and close the mandible in a hinge manner. The position of the condyle when
this movement occurred was not a retruded position or a forced position but a
position when the condyles were seated in the glenoid fossa as far posteriorly
as they would go by their own muscular power. This position but a position
when the condyles were seated in the glenoid fossa as far posteriorly as they
would yo by their own muscular power. This position was centric relation.

232

Cohen further stated that once the hinge axis points had been located and
marked permanently it was never necessary lo repeal the procedure since the
anatomic structures they represented never changed during life. The following
benefits were derived from a hinge axis record;
1.

Study models could be mounted to determine if the patients own centric

occlusion was in harmony with centric relation
2.

Working models could be mounted in the best relationship for the teeth

or denture bases.
3.

The vertical dimension could be increased or decreased on the instrument

tt ithout disturbing centric relation.
A later article by McCollum (1960) reviewed early work on the hinge axis.
discussed his personal investigations (including the development of an
articulator). and commented upon the hinge axis and mandibular movements in
detail.
Lauritzen & Bodnre (1961) used fifty patients to determine variations in
hinge axis location when compared with arbitrary methods. They found that
their method of hinge axis location gave 67% of the points at a distance of 5 13mm from the arbitrary points. When the arbitrary centre was changed to an
area of 5 mm radius. ony76% of the hinge axis locations were within this.
Trapozzano & Lazzari (1961) discussed the opinions of workers such as
Komfield( 1955). Granger (1952. 1954). Sloanc (1951). Collett (1955) and
Kurth and Feinstein (195 I) during the report of their studies into hinge axis
determination.

In view of the differences of opinion they decided to re-

examine two problems (i) whether there was a terminal hinge, and (ii) if there
was whether or not only one existed. The investigators located what they
thought to be the terminal hinge axis is fourteen subjects, but left the final

233

decision to a group of neutral observers. They found that 57.2% of the subjects
had more than one condyle hinge axis pint on cither one or both sides and
concludcdihat the high degree of infallibility attributed to hinge axis points
should be seriously questioned. It is interesting that this conclusion differed
somewhat from early statements made by Trapozzano (1955) concerning the
hinge axis.
This work was followed up by the same investigators (Trapozzano and Lazzan
1967) when they again found the presence of multiple hinge axes. They also
thought it essential that the technique of hinge axis location should be
undertakes by two operators; one to observe the opening and closing of the
mandible and the other to examine for rotation or translation of the stylus.
Relaxation of the patient during hinge axis determination was also considered
essential. Any alteration in vertical dimension was

contra indicated unless a

new interocclusal record was taken because of the presence of more than one
hinge axis. The investigators also confirmed what had been stated often, viz.
they found a number of hinge axis points along tracings of condylar inclination
which showed that rotation could occur in protruded positions of the mandible.
Using a modified hinge axis locator, with two styli, they also found that both
styli remained stationary on a hinge axis during opening and closing. Since it is
not mathematically possible fora rotating body to have two different axes of
rotation at the same time, these results of Trapozzano

and Lazzari (1961,

1967) must throw doubt on the accuracy of hinge axis location as it is practiced
today.
The subject of transographics appeared again when the secretary to the Midstates Odonto-occlusal symposium (Slavens 1961) asserted that there was no
single, inter condylar transverse axis common to and passing through both
condylcs. He said that articulation methods based on such assumptions usually
lead to poor results and that the Transograph was the only articulator to

234

duplicate essential jaw functions accurately, according to views expressed in
the symposium.
Schweitzer (1961) used still and motion picture photography to study
masticatory function. One of his findings was that posterior border or hinge
closure about the transverse axis in the condylcs did not appear to be reached in
functional chewing when viewed in the sagittal plane.
LauriUcn and Wolford (1961) carried out experiments on apparatus they had
designed to determine the accuracy of hinge axis location. In so doing, they
hoped to reduce errors in the machining, which Borgh and Posselt (1958) had
found had affected their results. A number of operators of differing
backgrounds carried out hinge axis locations on the apparatus, each person
having five attempts.
Group I were all people unfamiliar with the technique and they used 10 degrees
of mandibular opening. Group 2 were dentists who had seen hinge axis
locations carried out and had some slight experience of the technique. They
also used 10 degrees of opening. Group 3 were members of a study group
experienced in hinge AXIS location. They used the same degree of opening,
then 15 degrees of opening, and finally 5 degrees of opening- They found that,
of the 190 locations, all were within an area of diameter no longer than 1.5 mm.
and three were in an area of diameter greater than Imm. In the first group, 40%
of the locations were within an area of 0.2mm. in the second group 57% were
within an area of 0,2mm,and in the third group (10 dearees of opening) more
than 95% were within 0.2mm. With the latter group the same results were
obtained at !5degreesof opening for hinge axis location (with experienced
operators). With 5degrees of opening it became much more difficult to locate
thecorreel point but nevertheless 75% of the locations of group 3 were within
0.2mm of ihe axis. These results, where mechanical errors were reduced as

235

much as possible, were an improvement of 7% over Borgh and Posselt's (1958)
results and 4°/ over the results of Kurth and Feinstein (1951).
De Pietro (1963) stated that the only rotational centre which could function
independently in mandibular movement were the horizontal centers of rotation.
In a limited degree of mandibular opening, the condylar element, owing to the
limiting effect of the inferior surface of the glenoid fossa and the
temporomandibular ligaments, could brace itself superiorly and posteriorly and
thereby enable the horizontal centres of rotation to be located. Kurhter opening
led to translation as well as pure rotation which gave rise to different
instantaneous centers of rotation. He considered that, since rotational centers
did exist in mandibular movement, if they could be located in their natural
environment the possibility of a mechanical device «hich could simulate
mandibular movements was feasible. Much of De Pictro"s work was carried
out on an isolated mandible however, and as such this is nothing more ihan a
mechanical device.
Hickey et al(1963) used a pin inserted directly into the condyle and pin
attached to the lower incisors teeth for comparison when using motion picture
photograph} to record mandibular movements. Although they did not
deliberately locate the transverse axis of rotation of the mandible on the subject
under invesiigation. they found that during hinge opening the condyle pin
remained in a fixed position and rotated 5 degrees while the incisor pin moved
downwards 18mm without lateral deviation, and posteriorly 9mm. A lateral
deviation of 2.5mm occurred as the mandible reached its maximum opening.
The centre of rotation for the arc made by the incisor pin during the retruded
opening was not in the region of the condyle. They thought that the small
deviations over the tracing of the incisor pin during hinge opening may have
resulted from the irregularities of the surfaces of the cond>le and the disc as
rotation between the two surfaces occurred.

236

Aull (1963) published a paper in which he described four main schools of
though regarding the hinge axis.
1. The absolute location of the hinge axis school, as practiced by Lucia (1953).
McCollum(1939. 1943). Granger (1952. 1954) etc;
2. The arbitrary axis school as practiced by Graddock and Symmons (1952)
3. The non believers, such as Beck (1959). who thought the axis to be
theoretical) possible but not practically acceptable;
4. The split hinge axis school who believed in the transgraphic theory, such as
Stevens (1961).
Aull performed experiments to show the relative accuracy of the method used
to locate the terminal hinge position and demonstrated the fallacy of the split
axis theory. A simple but effective idea was to use two sets of flags and two
styli. Once set was positioned near each condyle and the other set was
positioned 4-5 includes normal way. Holes were drilled through the flags at the
rotation centers after the apparatus had been removed from the patient) and it
was then found to be possible to shine a light which passed through all four
holes. The points of all four styli also corresponded to a piece of elastic
stretched through all four holes. A colleague of Aull made a model of the lower
jaw with a Meccano set and showed that even when the axes were at different
levels there was still one common axis line through which the "mandible"
opened, even though this was not in the sagittal plane bul was at an angle to it.
La Pera (1964) stated; 'The hinge-axis expresses a relation of border
movements which involve or include the limits of all physiologic movements.
The hinge axis represents to the occlusal vertical dimension what the needle
point tracing docs to centric relation. He stated that there was no great
difference between human hinge axis movements and those of ihe articulator.

237

The hinge axis is though to be key to jaw movements. Once this had been
determined, its relationship to the anatomic elements of articulation could help
in the understanding of the physiology of the lemporomandibular joint. A
distinction was made between the kinematic hinge axis and the inter condylar
axis, the latter being above and in front of the former.
Schweitzer (1969) was of the opinion that hinge axes did exist and that it was
possible to locate them using a hinge bow. He disagreed with the idea that the
hinge axis was constant to the mandible and accompanied it no matter what
position the mandible assumed in function. He thought that translating
condyles had constantly changing axes once they left the hinge position. With
regard to articulators, he said that 'semi adjustable' ones and simple techniques
in his hands gave results equally as satisfactory as those obtained with fully
adjustable articulators and more complex techniques.
Long (1970) described an intra oral technique for locating he terminal hinge
axis by using two accurate centric relation records at two different degree of
jaw separation. Criticizing this paper, Naylor (1970) stated; they also claim thai
a trained hinge movement is possible and that the patient can be trained to keep
the condyles stationary in the fossae during rotation of the mandible. This is not
true.' He explained this by stating that a fixed axis of rotation could not change
its position in relation to a rigid body.
Ramfjord and Ash (1971) stated that hinge axis movement in the
tcmporomandibular joint could occur, theoretically, ai varying degrees of
protrusion, but that reference was usually made to the stationary hinge axis
movement with the mandible in centric relation. The relrusive opening
movement around the terminal hinge axis could be performed only to about 2025mm of anterior opening. Although the posterior part of the temporal muscle
held the jaw back during such movement. the pattern could also be duplicated
by manipulation of the jaw provided the patient was relaxed and pain or

238

muscular dysfunction was absent. This position of the mandible which gave a
hinge opening was also called by them centric relation, terminal hinge position,
or retruded contact position. Since it was determined by the ligaments or
structures of the temporomandibular joints, it could also be called the
ligamentous position. For this centre of rotation and mandibular movement
path to be constant and reproducible, they said that the condyles had to be
sealed against the menisci within he glenoid fossae. This assumed normal
function of the ligaments and jaw muscles. They also pointed out that
continued opening below the limit of hinge opening would lead to the centre of
rotation changing to a position slightly behind the mandibular foramen as the
condyies moved downwards and forwards.
Knap, Espinoza and Ziebert (1973) carried out studies to
1.

Compare the hinge locating range as seen on a sagittal tracing plate with

the clinical hinge locating range as observed at the hinge bow stylus point:
2.

To determine the amount of clinical hinge locating range that was lost by

the use of the closed occlusal clutch;
3.

"To calculate and analyse the actual distance of the hinge locating range at

infradentale.
They stated that the optimum range available using a closed occlusal clutch and
metal flags attached to the maxillary rod was 12.5mm; the optimum hinge
locating range available using a closed occlusal clutch and graph paper
attached to the skin was 3.4 mm and the amount of hinge locating range
occupied by the closed occiusal clutch at infradentale was 5.2mm.
Rani (1973) made a comparison of the biomechanics of the human masticatory
muscles using a stationary axis of rotation located at the centre of the condyte
and a moving instantaneous centre of rotation.

239

Yohn (1974) used cinefluorography lo determine a new anatomical reference
point on the skin surface which could be used when transferring maxillomandibular relationship to an articulator. However, the determination of this
position was made when the teeth were in the position of centric occlusion and
this could lead to error if this position did not coincide with centric relation.
Smith (1975) compared three methods of determining centric jaw relation to
determine which would consistently register the most retruded position, how
much variation there was between the methods, and the clinical significance of
this variation. The three methods compared were the terminal hinge axis.
Gothic arch apex, and an empirical method. He concluded that the empirical
method gave a centric relation point anterior to that of the other two methods,
and that the Gothic arch apex and the terminal hinge axis gave substantially the
same position. Te gothic arch method was the most precise and the empirical
method the least precise.
HiHoowala (1975) was the opinion, based on his radiographic studies, that
hinge movement took place in the upper compartment of the temporomadibular
joint as well as in the lower compartment.
Weinberg (1975) reported at length on his radiographic investigations into
temporomandibular joint function. The results of studies on a small group of
patients showed that, wiih half of them, condylar translation occurred during
hinge opening. This casts doubts on the validity of such recordings.
Rentier and Lau (1976) described a method of overcoming some of the
problems associated with hinge axis location on edentulous patients, such as
the resiliency of the soft tissue and the instability of clutches.
Jaarda, Clayton and Myers (1978) stated that, historically, the terminal hinge
axis has been ihe cornerstone of pantography as used in dentistry. The said that
the hinge axis of the articulator must be a duplicate of the hinge axis of the

240

patient otherwise there could be no mechanical reproduction of jaw motions.
The purpose of their study was to determine if the use of the terminal hinge
axis in transferring the pantograph to the articulator resulted in statistically
different cusp pathways and differences in ridge and groove direction and cusp
height who compared to the use of an arbitrary hinge axis. They used a linear
variable differential transformer mounted within a Denar D5 articulator to
measure cusp pathways. The studies were carried out on two patients and
showed statistically different cusp pathways when compared with the use of an
arbitrary hinge axis.
Preston (1979) discussed the history and development of the hinge axis
concept, particularly in relation to collinear and non collinear theories. He
outlined research which he had carried out on himself which showed
colineariiy of the contra-lateral styli in only four out of nineteen valid
measurements.
Winstantey(1979) carried out experiments to determine the accuracy of hinge
axis location using clinical methods on articulator. He found errors occurring
up to an area 2.4mm in diameter, although most results were most accurate. An
opening of 15 mm in the anterior region of the articulator gave better results
than I Omm opening.
Walker (1980) carried out 444 hinge axis locations in an attempt to correlate
the true hinge axis with various arbitrary or average locations. 1 le concluded
that an arbitrar> hinge axis does not exist, that any average position chosen
may lead to an inaccuracy of 6mm or more, and that very few individuals have
the same true hinge axis points on both sides of the face.
Razek (1981) determined the reliability of five methods used to locate the
arbitrary hinge axis when compared with compared with the kinematic hinge

241

axis. Although he thought none of ihe methods ideal, he found that palpation
gave resuils closest as the kinematic location.
Beard and Clayton (1981) carried out experiments to ascertain the reasons for
the discrepancy between the results of Trapozzano and Lazzari (1961. 1967)
(that more than one terminal hinge axis exists) and those of Aull (11963) (thai
only one lerminal hinge axis exists). They used improved recording apparatus
which they said eliminated some of the errors in previous work caused by
visual perceptions and concluded that there is online terminal hinge axis.
Lupkiovicz SM, Gibbs CH, Mahan PE, Lundccn HC, Ariet M, Sinkewiz
S14I982) This study investigated irregularities in hinge movement in 113
subjects.
These irregularities were analyzed by computer with an instantaneous threedimensional "screw1 axis method." The variation in hinge movement was
measured by ihe dispersion of the hinge axis instant centers. Dispersion of
instant centers was greater for muscle pain patients than for the normal,
indicating that instant center data could make a contribution to diagnosis and
treatment planning.
Gordon SR, Stoffer WM, Connor SA(1984) Incorrect location of the terminal
hinge axis of 5 and 8 mm to the anterior, posterior, superior, and inferior was
examined. With jaw relation records 3 and 6 mm thick at the incisors, the errors
in cusp height at the second molar ranged from 0.15 mm open space to 0.4 mm
excess height. The mesiodistal error ranged from 0.51 mm toward the distal to
0.52 mm toward the mesial. While the mesiodistal component to the error has
been calculated in the past with some accuracy, the values obtained have varied
because different anatomic dimensions were used. In addition, the vertical
component of the error in cusp height as illustrated in Fig. 2 was not considered
and/or not subjected to in-depth calculation.

242

Tsao DH(1986) On the basis of Newtonian principles of applied mechanics,
rotation around the mandibular hinge axis has been explored by separating this
rotation from translation of the mandibular hinge axis. After quantitative
comparison, it appears that hinge rotation is the primary physiologic movement
of the mandible, and that the Hanau qutnl provides compensatory factors in
facilitating hinge jaw movement. However, an unguided opening and closing of
the mouth usually consists of rotation and translation that are six-dimensional
in nature and very difficult to solve quantitatively without idealization and
differentiation. With an accurate three-dimensional image-measuring system,
such as computerized axial tomography, it should be possible to apply this
hypothesis clinically.
Abdal-Hadi L0989) A proposed arbitrary method of recording the hinge axis
based on the correlation between the profile width of the face and the kinematic
axis was compared with three commonly used arbitrary methods. The
investigation was carried out on 5 I individuals. The kinematic point was
recorded by the use of a kinematic locator. The different points of emerging
axes were photographed at a fixed distance by using a magnification
photoapparatus. The proposed method showed a regular distribution around the
kinematic axis. Furthermore, ihis method clearly illustrated that its highest
concentration was in the posteriosupcrior quarter around the true axis. The
proposed technique was found to be more accurate than the other techniques.
Vustin DC, Ricger MR, McGuckin RS, Connelly ME(1993) This study showed
that opening dynamics of the mandibular condyle could be studied by cine-MR|
and that an opening hinge axis appears to be located in the anatomic center of
the ccnd\lar head.

243

Degrees of freedom optoelectronic jaw movement recording system OKAS-3D
was used to record open/close movements in 10 asymptomatic subjects and 30
subjects with a clicking joint. Movement paths of the hinge axis and the
kinematic axis were calculated. A t-test was used in the analysis of the
locations of the two condylar movement reference points. Variances between
the values of the hinge and the kinematic axes were compared with the F-test.
Locations of the hinge axis and the kinematic centre on the average did not
differ significantly for the asymptomatic subjects at the group level (P>0. 05).
while individually the locations differed 4.96 mm on the average. The
difference between the hinge axis and the kinematic axis was significant for the
group of subjects with clicking joints (P<0.01), with the average individual
level difference of 9 mm. Variances differed significantly between the
coordinates of the hinge and the kinematic axes between the two groups of
subjects (P<0. 01). The study shows the importance of the choice of a condylar
movement reference point for the study of condylar movements and suggests
the use of the kinematic centre in such studies.
Hatzi P, Millstcin P, Maya A(20Gl):
STATEMENT OF PROBLEM: It has been reported that articulators are
interchangeable, which means that a clinician should be able to use one
articuiaior and send casts to a dental laboratory with the assurance that the casts
will be remounted with positional accuracy on a similar articulator. PURPOSE:
The purpose of the study was to determine whether mounted casts could be
transferred from 1 articulator to another with positional accuracy and whether
the hinge axis was reproducible in each of the articulators tested. MATERIAL
AND METHODS: This study compared left and right second premolars and
first molar occlusal contact areas with respective contact areas of like-mounted
casts. Five calibrated Whip Mix 3040, 5 calibrated Girrbach Artex AL. and 5
calibrated KaVo Protar articulators were tested, impact-resistant resin casts

244

mounted in occlusion on I articulator were transferred to 4 like articulators.
Each of the 5 articulators of each brand was opened and closed 10 times. Ten
vinyl polysiloxane right and left posterior interocclusa! records of the occluded
casts were made for each articulator. The use of a computerized image analysis
program provided quantitative measurements of light transmitted through the
occlusal records. A Kruskal-Wallis test was used for each of the 4 independent
variables of the study (molar differences, premolar differences, left differences,
right differences). By using a calibrated grid, a numerical assessment of
positional changes was made in millimeters. RESULTS: None of the articulator
systems was found to be exact, and no single articulator was an exact duplicate
of another (P<.01). The Whip Mix articulator showed greater deviation both in
hinge axis repeatability and in articulator interchangeabilUy than the KaVo.
The Artex articulator provided the most consistent hinge axis repeatability and
interchangcability of the 3 brands of articulators. CONCLUSION: The Artex
brand reproduced dental cast positions more consistently than the other
articulators tested.
CENTRIC RELATION
Philip Pfaff et al in 1756. the dentisl of Frederick the Great of Germany, was
the first to describe this technique of "taking a bite". This is known as the
"mush", "biscuit", or "squash" note.
Christenscn in 1905 was one of the early authors to use "impression wax" for
"bite" records.
In 1910, Greene described a mush bite made from modeling compound in
which he used a plaster wash to achieve a more accurate record.
Functional records were described in dental literature as early as 1910. Greene
used pumice and plaster mixture in one of the rims and instructed the palient to
grind the rims together. The denture teeth were set to the generated paths.

245

In 1923, Hanau wrote. "The most naive of our geniuses had intuitions, molded
into metal, attached a decorative theory onto their accomplishment and. it must
be admitted, they found a goodly number of fanatical believers and blind
followers, whose mental inertia probably did not care to penetrate even the
polish of the nickel-plated instrument under consideration.
In 1927, Hanau concluded that the Gysi tracing was satisfactory to check
records, but that universal usage was not good.
In 1929, Slansbery introduced a technique, which incorporated a curved plate
with a 4-inch radius (corresponding to Monson's curve) mounted on lhe upper
rim. A central bearing screw was aitached to a lower plate was injected to a
lower plate with a 3-inch radius curve (reverse-Monson curve). After the extra
oral tracing was made, plaster was injected between the plates to form a
biconcave centric registration. Hall (929) used Stanbery's method but
substituted compound for the centric relation record.
Kingery, R.H. in 1952 concluded that there are many excellent methods or
techniques all of with are capable of producing acceptable results. However,
the criteria for final acceptance of their accuracy, 1 feel, are and always will be
dependent upon the honesty, judgments and intelligent vision of the operator.
In 1954, Brown recommended repeated closures into softened wax rims.
Greene had his patients hold their jaws apart for 10 seconds to fatigue the
muscles and then had them snap the rims together. He then made lines in the
rims to orient them after removal from the mouth.
Shildkraut's paper was strongly criticized by Rinchuse (1955) who believed
CR and CO are like apples and oranges and, thus, not comparable. He wrote in
this regard, the Shildkraut et al. Article appears to be an ill-founded attempt to
relate a lot of nonsense of orthodontic diagnosis. Shildkraut believed that,
assuming CR and CO are different in all patients, this is not indicate of TMD or

246

any other problem in orthodontic diagnosis. Richuse objected to the idea of CR
mourning in orthodontics and believed that gnalhology in a thing of the past
that should not be applied to the principles of orthodontics.
Uinchusc (1955) had an opposing view again, and repeated his claim that these
two positions are not comparable and thus, the basis of the study is flowed. Me
summarized is criticism as follows "Because the study by Dr. Utt is descriptive
rather than experimental (Longitudinal/Prospective) or observational (crosssectional/retrospective), it must have a "sound" theoretical basis. I found the
basic premise for this study faulty. Furthermore, the methodology of this study
is tenuous. In addition 1 am still not certain what Dr Utt's study was about.
Since he did not directly define CR and CO. I do not know for sure what was
actually recorded and measured in the study.
Hodge and Mohan (1967) investigated the mandibular movement between
what we call today CR and CO even though the title of the study was "A study
of mandibular movement from CO and Ml". One hundred and one adults were
examined to determine whether there were any CR-CO slides and, in the
presence of a slide, the extent and direction was measured. It was found that
almost half the subjects did not have either antero-posterior or vertical
mandibular movement from CR to CO. As for lateral movement. 15 subjects
showed this component of movement.
Atwood D.A. in 1968 said that there still is a need for a simple terms with
describes the jaw relation in with the teeth, joints, ligaments and muscles are in
functional hormones and the teeth are in maximal occlusion.
Glickman 1 el al in 1974 concluded that "two complete fixed prosthesis built
with the occlusion in centric relation and with occlusion in the subjects existing
centric occlusal position were tested with telemetry under conditions of actual
use. The findings indicate that the subject did not use the centric relation

247

position but accepted the prosthesis built to her pre-existing centric occlusion.
These findings were consistent with their previous results of telemetric studies
conducted on patients with 3 unit fixed prosthesis.
McNamara and Henry (1974) titled their study "Terminal hinge contact in
dentitions", although the aim was to investigate the number of tooth contacts in
CR and CO. Cephalometric radiography was used to compare the positional
differences between CR and CO qualitatively. Eleciromyography was also used
to compare muscle contraction between the two positions. A positional
difference between CO and CR was demonstrated in all 15 subjects. However,
temporal and masseter muscle activity during maximal isometric contraction
did not differ significantly at these two positions.
One of the most often quoted studies in the field of CR-CO is by Glickman et
al. (1974). In this study a completely reconstructed, natural dentition was
studied under conditions of actual function to determine which of the two
occlusal relationships the patient used during chewing and swallowing. Multifrequency radio transmitters were constructed and inserted into the pontics of
full mouth restorations. Two fuil mouth restorations were made for the patient,
one in CO and the other in CR. Telemetric testing with the patient chewing and
swallowing was performed and the resultant tooth contact patterns were
recorded before ad after preparing the restorations. They found that the
prosthesis with intercupsalion in CR did not alter the tendency for tooth
contacts to occur in the patients CO. The patient had difficulty in achieving Ml
when allowed to close freely with the prosthesis designed to inter cuspate in
CR. They concluded that the use of the terminal hinge (the term 'lerminal hinge
position' was used as a synonym for CR in this study) in oral rehabilitation is
subjected to question since it appears that the patient would not function in this
position. It was suggested that the use of CR as a reference position is doubtful
because ihc distance to the existing CO position is variable and unpredictable.

248

Shafagh I. et al in 1975 conducted a study to investigate diurnal changes in
centric position within a period of one day. They made the following
conclusion, a. Sequential registration of centric position was exactly repcatable
in a few patients, but for most, a dispersion pattern resulted which varied
among individuals. The greatest variability registered at the level of condyles
was mostly supero-inferior, with little mediolaieral variability. There was no
single time of minimum variability common to most subjects.
b. in many subjects, records obtained in the morning showed the most antero
inferior position of the condyles and these made at night showed the most
postero-superior positioning the condyles. This indicates that centric relation
follows a diurnal rhythm with might be due to varying shapes and varying fluid
content of the temporomadibular joint.
c. If the most retruded and superior position of the condyles is desired, the
evening seems to be a belter time for making centric relation to records.
This study supports the theory of incorporation of some degree of freedom in
centric position in prosthetic restorations. It appears conceivable that diurnal or
periodicity analysis of centric relation will open a new dimension in dentistry
and prosthodontists.
Guichet, N.R(1977) in his study of biological lows governing functions of
muscles that move the mandible has drawn following conclusions.
Many factors, other than the proprioceptive inputs originating from occlusal
contacts on teeth, program jaw position and ihe functions of the muscles that
move the mandible. However, once the mechanisms by which specific occlusal
contacts program specific muscle functions in clearly understood, it becomes a
relatively simple matter to make an accurate diagnosis and select the most
direct approach io treatment.

249

Azarbal (1977) compared three occlusal positions; CR. CO and Myo-monitor
positions. Bxtra-oral clutches were used io compare the three positions anteroposteriorly and laterally. The study indicated that the Myo-monitor position
was almost always anterior and lateral to CR and CO. The author rejected the
use of the Myo-monilor as a suitable method for jaw positioning because the
method was not capable of locating the jaw as far posteriorly as possible.
Today such a conclusion based on these findings cannot be drawn.
Williamson, E.H. in 1978 conducted laminar graphic study of mandibular
condyle position when recording centric relation and concluded that "the
condyles to be significantly more superior in glenoid fossae when anterior
guidance was used. The difference in antero-psoterior positioning of the
condyles appeared to occur randomly
Guichet N.F. in 1978 staled that
a.

A model to quantify muscle response to occlusal contacts is useful in

developing an under standing of the mechanisms by with the occlusion
programs muscle function. Knowledge of how occlusion programs muscles
function enables the dentist to develop manipulative skills of the mandible with
are necessary for diagnosis and effective occlusal treatment.
b.

The character of the occlusal surfaces of the teeth programs the functions

of muscles that move the mandible and imposes specifications upon the dentist
with in with he must work in manipulating the patient's mandible. If he exceeds
those specifications, protective responses that inhibit his efforts are elicited in
the patient's musculature.
Numerous studies have reported that the majority of patients with a natural
definition show a discrepancy between the occlusal position of the mandible in
CR and MI (Posselt. 1952; Hodge and Mahan 1967; Rieder, 1978). This
discrepancy is present in least 90% of dentitions, and Posselt (1952) indicated

250

(hat the antcro-posterior distance between the retruded (now CR) and the ICP
position was about i .25 mm (+ 1.00) on average. This discrepancy was found
to remain constant even following successful orthodontic treatment. In
children, the distance was smaller (0.85 +0.6 mm).
Rieder (1978) authored an epidcmiological study of 323 adult patients to find
the prevalence and amount of mandibular displacement from retruded contact
position (RCP) (CR) to inter cuspal position (IP) (CO). Direct clinical
measurements revealed that 86% of the subjects had mandibular displacement
from CR to CO in one or more directions of movements. All of the patients
with mandibular displacement demonstrated a vertical component or
movement, nearly as exhibited an anterior component, and a third showed
lateral movement.
Rosner and Goldberg (1986) designed a study to investigate three-dimensional
difference between CR and CO. A custom made Buhnergraph on a Whip-mix
articulator was used to indicate the differences. Records of 75 patients
indicated that 60% of the CO records were placed anterior and inferior to CR.
There was no CO marking on the posterior superior quadrant suggesting that
CO is unlikely to be posterior and superior to CR.
G. Newell wood in 1988 discussed a physiologic clinical approach to
developing an optimum mandibular posture and clinical methods of recording
this posture when rehabilitating complete occlusion. Its theme is stabilization
and education before registration.
Shildkraut et a) (1994) were among the orthodontists who strongly believed
that hand held articulated casts used routinely in orthodontic treatment planning
should be replaced with the so called proslhodontic mounting with face bow
and CR records. They also criticized the use of conventional lateral
cephalometric radiographs for orthodontic diagnosis because such radiographs

251

are taken with the patient in CO. They commented that cephalomelric
radiographs should be transferred to CR radiographs and the treatment planning
and tracing of the radiographs be based on the modified CR radiographs. They
designed a study to determine if there was a significant difference between 24
cephalometric measurements of mandibular position derived from a CO tracing
compared with those of a converted CR tracing. They hypothesized that:
providing statistically significant differences exist between CR and CO, this
could affect the diagnosis and treatment planning necessary to correct the
malocclusion. A radiographic conversion method, devised bySlavicek (1988)
was used to modify CO cephalometrics. A SAM articulator and mandibular
position indicator was used to indicate the differences in the models. CR and
CO tracing on radiographs were also compared by computer soft ware. It was
found that mandibular positions were significantly different between a CO
tracing and the same tracing converted to CR. The condyle was always
vertically displaced and most often positioned distally when the teeth were in
CO. It was concluded that, to avoid errors in diagnosis, treatment plans should
be formulated from lateral cephalograms that have been convened to CR.
Later, Rolh (1995), Williams (1995a, b). Carter (1995), Chubb (1955), Hew
(1966) and Alpern (1996) defended Utfs position and emphasized that a
requirement in orthodontics is the necessarily of accurately mounted study
casts. Williams said; there is no way you can evaluate condylar position and
functional occlusion without the use of an articulator. I challenge any one on a
clinical level to disprove that statement. The academicians must get their heads
out of the scientific clouds and come back, to reality. The fact that one is astute
at doing research does not makes one a good clinician. In fact it is usually the
opposite. That is why they are in research.

252

INCISAL GUIDANCE
Clyhde H. Schuyler in 1963 staled "in the hands of most demist, complete oral
rehabilitation can be more satisfactorily accomplished by functionally
generated path technique than by the use of complicated articulating
instruments. It can be accomplished in less time with fewer problems and
failures and with less strain on the patient and the dentist. The coordinating of
the occlusion is recognized as one of the most important and most complicated
facts of practice of dentistry. Many articulating instrument and techniques have
been confusing to practicing dentists less complicated procedures for
developing occlusal coordination add to the pleasure and happiness of both
patient and demist.
Robert R. Scaife J.R in 1969 from the results of this study, it can be said tha the
natural occurrence of a cuspid protective mechanisms is relation large (57%)
but by no means over whehningly predominant. Thai it occurs in the majority
of subject studied would indicate that this type of occlusion is ideal. The huge
(91.5%) number of subjects with cuspid contact in CO. would be a negative
factor in the decision of the idealism of a cuspid protected occlusion, if in fact
proprioceplor abilities our lost through continuous contact. The faceting
statistics seem to be favorable to the cuspid protection theory,
J. Marvin Reynolds in 1971 proposed an occlusal pattern which organizes the
teeth to permit group function as well as mutual protection. The main load to
centrically related jaw closure is borne by the posterior teeth. The anterior teeth
protect the posterior teeth in centric closures. The incisors, canine or posterior
teeth mav function in dependent of each other. All the teeth remain just outside
the routine functional arena of cyclic motions. The muscles are permitted to
move the condyles to an> position in the joint compartment in eccentric
occlusal positions without guidance or interference from the teeth.

253

Timothy..]. O' Lealy in 1972 stated, "The mobility of teeth was assessed in 30
ma.\i11ar> quadrants of each of two groups of subjects. One group had a
cuspid-protected type of occlusion in the test quadrants of each of two groups
of subjects.
One group had a cuspid-protected type of occlusion in the test quadrants while
the second group had a group function type of occlusion. The mean mobility
was higher in the presence of a cuspid protected occlusa! pattern for each type
of tooth. The difference was statistically significant for the maxillary first
premolars. the first molar, and over all mean of the seven tooth types studied.
D. Blake. M.C.Adam in 1976 concluded
1. Tooth loading with cuspal guidance in canine and group function occlusions
has been discussed.
2. Canine guidance and group function guidance occlusion are considered
normal; the latter occurs naturally due to occlusal wear.
3. When an entire occlusion is to be restored, either occlusal scheme will serve
adequately.
4. Where only a portion of the occlusion is to be restored, the restoration must
be consistent with existing occlusal scheme.
5. Regardless of with occlusal scheme is used, the dentist must maintain it
during regular post operative appointments.
Arthus Edward Kahn in 1977 stated. "Organized disclusion by the canines
should find the canines paired in proper rotated stances so that in any of the
possible movements of laterotrusion. the tip of the lower canine engages the
mesial groove of the upper canine. In effect, this means that a cl.-I centric
relation occlusion is requisite to such a rotated stance of the canines; other

254

wise, wear of the teeth may occur. Thus, the importance of properly executed
orthodontics in the preservation of stomatognathic system becomes critically
apparent.
Walter Donald Heinlein 1980 The lack of more specific instrumentation in
rebuilding anterior teeth still leaves much to the individual dentist in making
value judgements. However, this apparent failing is the same reason that makes
this part of resloram e dentistry so exciting.
Torster Jemt and Jundquist in 1982 concluded that the chewing pattern may
be influenced by the type of occlusion irrespective of the existence of maxillary
canines
E.H. Williams in 1983 stated that only when posterior disclusion in obtained
by an appropriate anterior guidance can the elevating activity of the temporal
and masseter muscles be reduced. Further, it is not the contact of the canines
that decreases the activity of the elevator muscles, but the elimination of
posterior contacts.
Shoji KoKuo in 1987 concluded that "The inclination of the sagittal incisal
path, with is transferred to the incisal table of an articulator as anterior
guidance, should be equal to the inclination of the patients condylar path. It is
of course possible to make the incisal. Path steeper then the condylar path to
some extent; however, it should not be more than 25°steeper. Similarly the
incisal path should not be much flatter than the condylar path.
Sumiya Hobo in 1991 concluded that molar disclusion is determined by the
cusp shape factor and the angle of hinge rotation. A new twin table technique
has been introduced for developing molar disclusion by use of two incisal
tables. It is relatively in complicated technique and does not require special
equipment. The final prosthesis by use of the twin tables techniques results in a

255

restoration with a predictable posterior disclusion and anterior guidance in
harmony with the condylar path.

256

FUNCTIONALLY GENERATED PATH
By Fredrick S.Mcycr (195?) This article discussed the use of the generated
path technique in FPD construction. If all procedures have been completed
correctly. the finished fixed partial denture will fit the dies on the aniculator
with no tension or distortion. It will fit the patient's moulh in a similar manner,
and correct balanced occlusion and function are insured.
By William L. McCrackan, (1958) It is not expected that the silver plating of
a wax occjusal record will receive wide acceptance because of the added step
of electroplating. Bui just as there are those who prefer to work with
electroformed dies. So there may be some who would prefer to set teeth to an
initial template. It is hoped lhai this procedure will contribute something
toward better RPD occlusion.
Robert G. VIG (1964) A technique has been described by which the patient
chews in a centric record of his own jaw movement in gliding and masticatory
mandibular excursion. The technique is most advantageous for the construction
of complete dentures against natural or mixed dentitions. The technique, with
modifications, is of value in numerous partial and immediate denture situation
in which articulator movements can not duplicate natural movement with in a
range of movements and harmony that is with in the accommodative ability
limits of the patient.
Fred S. Meyer (1954) We believe that any one can use it with equal success. It
requires no special skills. It will work in any man's hands.
Clyde H. Schuyler (1959) functional coordination of the occluding surfaces of
the tceih has been spoken of as one of the most important sciences in the
practice of dentistry. The incisal guidance, and is normally the inclination.

257

RECORDING VERTICLE DIMENSION
In 1771, Hunter wrote "In the lower jaw. as in all the joints of the body, when
the motion is carried to its greatest extent, in any direction, the muscles and
ligaments are strained and the persons made uneasy.
In 1906, Wailisch described mandibular rest position an that position of the
mandible where in alt muscles action is eliminated and the mandible is
passively suspended. I le reported that in this positive the opposing teeth do not
contact.
In late 1920's Sichcr and Tandlcr restated the role of the musculature in
controlling the posture of the mandible. They stated, "the rest position of the
articulation, the "middle position" is that in with the mandible is at a slight
distance from the maxilla.
In 1946, Thomson reported on the cephlometric analysis of the rest position in
edentulous and semiedentulos adults. He stated that the rest position was stable
and that it could not be permanently altered by prosthetic restorations.
However, in 1954 Thompson, somewhat qualified his earlier statement of the
immutability of the mandibular rest position of a given individual. He
recognized that the rest position is related to the variation in tonicity of the
involved musculature.
Farhad Fayz in 1958 concluded that the variations in the measurements of
different teeth conformed the anatomic individuality of each patient.
Nevertheless the finding of this study will be helpful as guides in the initial
placement of the maxillary and mandibular anterior teeth and in the initial
determination of the vertical dimension of occlusion of the lingual surfaces of
six upper anterior teeth, might be considered an the key to a harmonious
functional relationship of the natural dentition or the key to functional

258

occlusion and finally roentgenogram of TMJ should be made. Some badly
disorganized occlusal problems present as abnormal positioning an a very
necessary protection for the dentist of discomfort and complication should arise
following a complete oral rehabilitation
Boucher (1959) The registration of closing force with the Boss Biometer
cannot be classed as an objective method for determining vertical dimension.
Yahia H. Ismail (1968) The roentgcnographic cephalometric investigation
done to evaluate the swallowing technique for determining the occlusal vertical
relation in edentulous patients. The findings are
1.

The occlusal face height after prosthetic treatment showed an increase

ranging between 0 and 5 mm. with a mean increase of 2.8mm, as compared to
occlusal face height before the extraction of teeth. This increase was
statistically significant.
2.

A significant co-relation was found between the number of posterior teeth

missing before extraction and increase in occlusal face height as determined by
the swallowing technique after the patient becomes edentulous.
The swallowing technique presented a direct approach to the problem of
establishing the occlusal vertical dimension in edentulous patients
Allyn G. Wagner (1971) The rest method, based on natural relaxation to be an
acceptable method to determine the rest position, because the measurements
presented less high and low reading. The M. M. M method tended the produce
a large rest vertical dimension and the swallowing method a smaller one. The
instability of ihe mandibular rest position was of similar magnitude for all of
the methods tests .
A.J. W. Turrel in 1972 concluded that many methods of assessing and
recording vertical jaw relation in edentulous patients have been presented and

259

evaluated. When no accurate pre-extraction records exists, the dentist must rely
upon esthelic appearance supplemented by aids with an after misleading.
Sidney I. Silverman(1985) concluded that ; dentist measure the anticipated face
height of a patient when a mandibular trial base and occlusion rim simulating
the form of finished denture is placed in the mouth wiihout a maxillary trial
base and occlusion rim. This measurement can be an appropriate guide for the
vertical dimension recorded lo generate a trial arrangement of prosthetic teeth.
SUMMARY
Objective of treatment
Having decided that a mouth requires the full treatment, what is our objective?
All these patients have one problem in common: stress and strain. Usually the
stress and strain is due to malfunction or to poorly related parts of the oral
mechanism. Occasionally, undue stress and strain on the oral mechanism is the
result of an emotional disturbance. Whatever the cause, whatever the reason,
the common denominator seems to be stress. Our problem, then, resolves itself
into one of minimizing these stresses so that, they are not destructive. The
stresses should fall within'the capability of the tissues to withstand them and
maintain a state of health. To accomplish this objective to the fullest degree
possible, it is essential to have an intimate knowledge and a very clear
understanding of the masticatory mechanism, of certain principles and forces. It
requires knowledge of how the oral mechanism is built and how it functions. If
excessive stresses are involved, we must reduce or minimize them so that they
will not be destructive. Granted that the muscles of the oral mechanism can
exert a certain amount of force, in order to prevent this stress from being
destructive the best thing to do is to distribute it evenly over as great an area as
possible: over as many teeth as possible, over the ternporomandibular joints,
over as much tissue as possible, and over as many cells as possible. This

260

approach makes sense. A given force distributed over as great an area as
possible reduces the stress per unit so that it can be tolerated by the tissues.
Aging tissues may not be able lo withstand the same stress as younger tissues.
This is why a malfunction is frequently tolerated at a younger age. Our
problem, then, becomes one of how best to distribute this given force or stress.
The oral mechanism consists primarily of the ternporomandibular joints, the
teeth and their supporting structures, and the muscles of mastication. We arc
concerned with the joints and the supporting structures. The teeth are the
means by w hich the stresses are going to be directed or transmitted. We know
from our anatomy and physiology that the temporomandibular joint is a siressbearing joint know \hat the supporting structures (bone) of teeth are designed to
withstand stress. Our objective is to distribute these stresses equally between
the joint, tissues and the supporting structures. Teeth will be the means by
which the forces are distributed.
Harmony of form and function
The tcmporomandibular joint has a definite pattern of function. If, in the
execution of this pattern of function, the teeth interfere, there is a clashing of
stresses in the mechanism. This will be true whether the stress is used to
masticate food or just to. "Punctuate" a swallow. If the tooth contact is not in
harmony with the temporomandibular joint pattern, then the entire stress or the
greatest part of it will be transmitted through the poorly related tooth to its
supporting structures. It may be more than those cells can endure. It would be
much better to have the tooth contact its antagonist at the same lime the
temporomandibular joint is in its best bracing position so that the force could
be evenly distributed between the supporting structures of the tooth and the
temporomandibular joint. Therefore, in centric closure (patients exert the
greatest force in this position) all the upper and lower posterior occlusal
surfaces should come together simultaneously. In addition, ideally, the cuspal

261

design would be one with a tripod arrangement. This stabilizes teeth by putting
stress in the long axis of each tooth where it is best resisted. The anterior teeth
barely come together in this position (centric closure). In all other positions,
when teeth are in contact, only the anterior teeth come together for incision.
The posterior teeth are discluded. preventing any rubbing of posterior occlusal
surfaces. Thus, the anterior teeth protect the posterior teeth in the excursions,
and the posterior teeth protect anterior teeth in centric closure.
The question frequently asked is: "Why do you need cusps?"
The main reason we need cusps is to be able to stabilize the teeth in the long
axis. Only with cusps is it possible to have tripodization, that is, a cusp making
contact with the sides of a fossa in opposing directions when in centric
occlusion. If this is properly done, in most cases, it is possible to avoid the
necessity for splinting weak teeth. However, the cusps must be correctly
placed. This brings up another often asked question: "Why do we heed the
accuracy of a pantograph tracing if teeth disclude in the excursions?"
Disclusion does not mean missing by several millimeters: ideal disclusion is
the passing of cuspal elements close together without rubbing. The cuspal
elements should operate like the blades of a pair of scissors -very efficiently
without self destruction. This means that the cuspal elements must be very
carefully placed. In order to correctly place the cusps, we must know the
character of the individual's jaw movements, and the most accurate method of
capturing and duplicating an individual's jaw movements is by use of the
pantograph and a fully adjustable articulator that will reproduce the jaw
movements. A very minor dividend to all the effort involved in restoring the
occlusal surfaces is that they look like natural teeth
In cases where there are no end teeth in the arches and removable restorations
must be used, it is very important that every effort be made to continue to

262

distribute the stress over as great an area as possible. This is accomplished by
means of mucostatic bases and well-articulated chewing surfaces. Rather than
putting additional stress on the already endangered abutment teeth, it may be
possible to give some stability'to weak teeth by using a good removable
denture. The use of precision attachments helps to minimize the strain on
abutment 'teeth. A mucostatic base is the only means by which a removable
case can be kept in proper function for any length of lime.
Wherever feasible, fixed bridges are preferable to removable bridges. The
possibility of maintaining an equal distribution of stress is greater with fixed
work than with removable: the distribution can be maintained longer with less
adjustment.
Method of Treatment
We must be able to treat the entire mouth at one lime to manipulate all the
chewing surfaces at the same time so that they can be the true mates they were
intended to be. "At the same time" does, not mean in an interval of hours, days,
or weeks: it means that before anything is completed, we would be able to
adjust or alter any of the surfaces if necessary. Extreme skill is necessary if
total treatment is to be accomplished by the quadrant dentistry method. Very
careful equilibration of the existing occlusion must be completed first. This
may be difficult to expedite, because teeth shift, making it necessary to repeat
the procedure several times. Then each quadrant of dentistry must be perfectly
executed. When all four quadrants are completed, further equilibration is
usually necessary. Any adjustment in the mouth is difficult and cannot be
accomplished as accurately or as easily as on an articulator.
The patient's temporomandibular movements must be accurately recorded and
duplicated in minute detail. This is tantamount to having the patient's head to
work on in the laboratory without the distracting factors of saliva, cheeks, and

263

tongue. Some dentists attempt to accomplish this directly in the mouth, but this
is almost an impossible task.
Before the preparations are made, it is necessary to determine which cusps are
essential and approximately where they will be located. This is extremely
important because it will influence the type of preparations to be used. How the
teeth interdigitate will determine whether full coverage or onlays are indicated.
Of course, onlays are by far the best choice. The veneer materials available
today arc a poor substitute, for nature's enamel and will never take its place.
The best-made restorations that are adjacent to gingival tissue can only be
irritants. However. sometimes the amount of cusp warpage that is necessary
will produce too great a display "of gold. In these cases, a compromise may
have to be made whereby we will resort to full coverage with its drawbacks.
The practical treatmenl of a case necessitates ihe completion of all the
preparations of the teeth involved. Usually this cannot be accomplished at one
sitting; nor should it be done thai way. So. we have to construct temporary
restorations for each quadrant as we proceed. When all four quadrants are
prepared, the master impressions are taken, and these casts are accurately
related to the articulator by means of a face-bow and a centric interocclusal
record. The prepared teeth will have the exact relation on the articulator that
they have in the patient's mouth. Quadrant impressions are taken as each
quadrant is prepared, and the quadrant casts made from these impressions will
be used for fina! margin and contact adaptation of the wax patterns. The
temporary restorations are usually made of good scrap gold and are in one
piece for easy handling during their frequent removal and insertion. Splinted
together, they also tend to maintain the status quo in the interim required for
laboratory procedures.

264

Because of improvements in our techniques and materials, it is now possible to
temporize most cases with acrylic splints -either processed or auto
polymerized.
An articulation is developed in wax on the master casts on the articulator. The
characteristics of ihe articulation will be a harmonious arrangement of the
occlusal surfaces mat will follow the movement of the temporomandibular
joint. The anterior teeth -overbite and over-jet will be coupled with the
posterior occlusal surfaces. Ihe wax patterns will be separated, transferred to
the quadrant dies, and the margins adapted. The patterns will then be cast in
hard partial denture gold and prepared for trial in the mouth.
Regardless of how carefully and accurately we work or think we work, these
castings are far from the finished product that the patient will wear. The errors
incorporated in cutting the wax patterns and transferring them to individual
dies, the investing and casting errors, the material errors -all add up
unbelievably. It therefore becomes necessary to correct the restorations before
they can be worn, liach restoration is carefully fitted to each tooth and lo each
other restoration. After the restorations have been fitted satisfactorily, we do a
"remounting," This means that accurate casts containing the restorations are
placed on the articulator in the same relation that they had in the mouth. This
step is accomplished by means of a face-bow transfer and a centric
interocclusal record. The restorations are the carefully adjusted until they
exhibit the same characteristics and relation to each other as the wax patterns
on the master casts. When this has been accomplished, the restorations are
ready to be worn temporarily by the patient.
There are several reasons for temporary wearing of the restorations, i lealing of
the supporting structures of periodontally involved teeth will frequently
produce a slight change in the positions of the teeth (and their restorations).
Malfunctioning joints often heal after proper function, with the result that there

265

is a slightly different relationship. Patients, after overcoming long-imposed
neuromuscular patterns of malfunction, will more readily give us accurate joint
relationships. If the restorations are temporarily cemented, they can be removed
without difficulty for slight adjustments to perfect the case. One needs but a
single experience of having to cui out a permanently cemented case to be cured
of being has in permanently cementing restorations! In very bad pcriodontal or
joint cases, it is often necessary have half a dozen remountings over a period of
several years before real success can be achieved.
Splinting -A Last Resort
Temporary restorations are splinted together both for convenience in handling
and because this tends to maintain the status quo.. In contrast, permanent
restorations are almost never splinted. Experience has shown that splinted teeth
never respond to treatment so quickly nor so well as individual restorations do
(provided the articulation is correct). There is one exception to this rule: only
after repeated efforts at stabilizing the teeth by means of individual restorations
have failed may we, as a last resort, solder these restorations in a splint. We
recognize this as a tlnal resource and a definite compromise, something to be
undertaken when it is the only way to maintain the teeth for a while longer. It
is never the ireatment of choice. When splinting is routinely used, it is only a
"cover-up" or a compromise for improper articulation.
Periodontal Therapy
Full mouth rehabilitation is performed to produce a healthy, esthetic, wellfunctioning, self-maintaining masticatory mechanism. It is often necessary to
institute good periodontal therapy to produce a healthy oral mechanism.
It is possible to eliminate pockets by periodontal therapy (conservative and/or
surgical). However, unless the function is corrected, pocket-free teeth can still
bounce around during function. Complete pocket elimination is less important

266

than stability in function. Experience has shown that pockets do not necessarily
get worse if not complete!) eliminated, provided that proper function is
established. Nevertheless, pockets should be carefully treated by frequent
curettage and adequate home care.
If the periodontal condition is not severe, it usually can be taken care of at the
time of tooth preparation. Curettage, electrosurgery, and even slight bone
contouring nay be performed when a quadrant is anesthetized for tooth
preparation.
When more sophisticated therapy is necessary and is to be performed by a
periodontist. cooperation by the prosthodontist is advantageous. The teeth can
be partial!) prepared and temporarily splinted. The periodontist can remove the
splint and do his or her periosurgery with greater ease and obtain better results.
After healing, the preparations are finalized. When the soft tissues are healed
and all the teeth prepared, then the reconstruction can be completed. When the
ultimate ideal is sought, definitive periodontal therapy should be protected by
definime occlusal therapy such as gnathology. However, bear this in mind:
unless the patient exercises diligent home care after treatment, even the best
therapy will fail.

267

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