DIAGNOSTIC AND MICROBIOLOGICAL TOOLS IN
ORAL AND MAXILLOFACIAL SURGERY
The role of the healing professions is to apply knowledge and skill towards
maintaining and restoring the patient’s health.
This may not always be completely attainable, but the clinician is expected to
strive for optimal results within the limits of the circumstances.
Diagnosis is the process of evaluating the patient’s health, as well as the
resulting opinion formulated by the clinician.
The art and science of oral and maxillofacial diagnosis is an integral component of
maxillofacial surgery. It begins the moment the surgeon meets the patient and continues
throughout their professional relationship during these interactions, dental health care
providers are responsible for the detection of numerous disease and abnormalities of the
oral and perioral region and for recognizing how much findings may impact the
systemic health of the patient.
As advances in medical diagnostic and treatment modalities continues to
increase the life expectancy of the population, the like hood of encountering patients in
dental practice with concomitant medical problems will also rise.
Thus, it will become increasingly important for practicing maxillofacial
surgeon to take through medical history, recognize signs of systemic disease and work
closely with their medical colleagues to ensure that safe dental care is rendered to these
THE DIAGNOSTIC METHOD:
Accurate diagnostic decisions rely on a systematic approach to the unique
diagnostic challenge posed by every patient. The most effective approach is the
application of the scientific method to clinical decisions which are referred to as the
1. COLLECTION OF INFORMATION:
This initial stage of the diagnostic method is the collection of the available
diagnostic information. This includes details verbalized by the patient, features
determined by the clinical examination and the data derived from adjunctive diagnostic
procedure such as laboratory cast.
2. EVALUATION OF INFORMATION:
The second step of the process is to organize this information and
determine its clinical significance; the clinician mentally compares the findings with
basic knowledge, such as anatomy and physiology, and with observation from past
Unusual findings as co-related to identify patterns and relationship that is
suggestive of certain diseases.
3. DIANOSTIC DECISIONS:
The clinician next formulates opinions concerning the nature of unusual
findings. Each opinion or diagnosis is the explanation for an element of the patient’s
status that is most consistent with the available information. This is comparable to
formulating hypothesis in the terminology of scientific method.
The reassessment stage of the diagnostic method is equivalent to
hypothesis testing from the scientific method. From this the surgeon can often predict
the response of the abnormality following treatment.
COLLECTING DIAGNOSTIC INFORMATION:
Several sources of diagnostic information contribute to assessment of
the patient’s status. The assembled diagnostic information for a patient is referred to as
the diagnostic database. This evidence of the patient’s initial status also provides a basis
for future comparisons to evaluate disease progression, the effectiveness of treatment
and the, and the development of new abnormalities.
The diagnostic database consist of the patient’s history, the physical
examination, results and the information obtained from adjunctive diagnostic
COMPONENTS OF THE COMPREHENSIVE DENTAL DIAGNOSTIC DATABASE
Principal racial and ethnic back ground
Name and address of:
Informant, if other than the patient
Family dentist or former dentist
Third party health care provider
Other data: ( like in medico legal cases)
History of present illness:
Past medical conditions
Infection and immunization
Known allergies and drug reactions
Current medical treatment.
General physical appraisal and vital signs
Extra oral examinations
Adjunctive diagnostic information:
Clinical laboratory studies.
Microscopic examination of tissue samples.
Consultation and referral.
The patient’s name, age, gender, race, address, phone number and
additional personal data are listed initially. This information is needed primarily for
patient identification and administrative purposes.
However, the patient age, gender and race may contribute to the
diagnosis of specific conditions.
The chief complaint is a statement of why the patient consulted the
doctor. The chief complaint should be recorded in the patient’s own words because this
may provide insight into the nature of the problem.
It is a response to the doctor’s question.
“What problem brought you to see me”?
Circumstance of injury
Exact nature of the injury
Nature of the object
Velocity and vector of traumatic force
Glasses / were worn.
HISTORY OF PRESENT ILLNESS:
It details the patient’s awareness of the problem.
Effectiveness of past treatment.
PAST MEDICAL HISTORY:
It is a review of health care experiences and medical conditions that
have been diagnosed. This information is usually organized into past diseases,
immunization, hospitalization, known allergies, current treatment including medication.
The family history consists of health status of family members. This may
reveal the possibility of conditions with a genetic tendency such as ischemic heart
disease, diabetes, hemophilia, communicable infections may also be suspected on the
basis of family history
These history help to identify psychosomatic imbalances, these findings
reflect the patient’s life style, which can indicate a vulnerability to certain disease,
exposure to specific infections or dental treatment preference.
The social history also includes the patient’s response to the demands of
routine and stressful personal events. These responses reveal that emotional adaptation
of patients to their surroundings.
It is a summary of past dental care, unusual dental experience, hygiene
practice and related topics.
It provides diagnostic information about the patient that is perceived by the
clinician with out the use of complex technical devices. This limits the surgeon to the
primary senses and a few simple instruments.
It consist of
General patient’s appraisal
Extra oral examination
Intra oral examination.
The examination of any portion of the body consists of 4 modalities.
These 4 words and the procedures that they represent have stood the test of time.
GENERAL PATIENT’S APPRAISAL:
Evaluation of the patient’s general appearance
Similar observation is referred as general pt appraisal.
Measure of the patient’s vital signs which consist of
History of vomiting
History of bleeding from ears and nose
History of CSF leak
History of unconsciousness
History of amnesia.
6/6 or better
6/18 – 6/24
6/36 or less
No light perception
Malar fracture type
Blow out (V)
Present (diplopia or squint)
The trauma score was developed by champion et al; to quick assess the extent
of injury to vital systems and the severity of the injury to vital systems and the severity of
the in injury to provide triage and treatment of the patient.
The trauma score provides a means of characterizing the physiologic status of
injured patients` cardiovascular, respiratory, and neurological systems. The Glasgow
coma scale (GCS) is incorporated to evaluate the neurological status and assess the
degree of craniocerebral injury. The GCS evaluates the eye opening response, best verbal
response, and best motor response, with a score given for each response. Scores range
from 3-15 with highest numbers representing an increased degree of consciousness.
EXTRA ORAL EXAMINATION:
The extra oral examination consists of the physical findings beyond the
general appraisal that can be perceived without looking in the patient’s mouth.
The extra oral examination by the surgeon is focused on the head and
neck although examination of other region may yield significant information.
INTRA ORAL EXAMINATION:
The intra oral examination includes all physical findings within the oral
ADJUNCTIVE DIAGNOSTIC PROCEDURES:
Adjunctive diagnostic methods rely on “distant” sources of information such
as complex diagnostic instruments and other clinicians.
These procedures extend and support the clinician’s primary senses or
enhances the accuracy and assessment of past health information.
Radiographic examination is an example of routine adjunctive diagnostic
procedures that is essential to the practice of dentistry.
Clinical laboratory studies such as blood counts and microscopic
examination of tissue samples are examples of adjunctive procedures that are
contributory in specific situations.
In a darkened room on the night of Nov 8 1895, a tiny bit of
fluorescence, which was to enlighten the entire medical world was noticed by Wihelm
Conrad Roentgen. All too often, even before the history and physical examination have
been obtained, a radiograph is the first procedure completed for a patient in the dental
Although many unsuspected pathosis are discovered by routine
radiographs, the primary role of radiographs is to confirm clinical impressions.
Consequently the radiographic examination should follow the completion of the history
and physical examination and only the views that will contribute to the recognition of
the malady will be secured.
Radiographs should never be accepted as the sole criterion for an operation.
Views that are appropriate for the study of oral and perioral lesions and that may be
made with dental radiographic units include.
1) High definition intra oral views, commonly called periapical films.
2) Occlusal views
3) Extra oral views of the jaw.
i. Transparietal projection--------TMJ
ii. Transpharygeal projection------Head and neck of the condyle
iii. Oblique lateral projections------Posterior body and ramus of mandible
Body of the mandible
Anterior body of the mandible
Skull and bone series
1. cephalometric projection---------Anterio posterior, lateral
2. Anterio posterior projection ------Mandible, Paranasal sinuses and lateral
INTRA ORAL RADIOGRAPHIC EXAMINATION:
Intra oral examination is the back bone of dental radiography. There are 3
categories of intra oral radiographs.
Periapical radiographs are intended to show all of a tooth including its
surrounding bone. Bite wing radiographs show only the crowns of the teeth and
adjacent alveolar crests.Occlusal radiographs reveal an area of teeth and bone larger
than periapical films.
EXTRA ORAL RADIOGRAPHIC EXAMINATION:
Extra oral radiographic examinations include all views made of the orofacial
region with film positioned extra orally.
Lateral oblique projections:
Two lateral oblique projections are commonly used to examine
the mandible, each showing a different area of the mandible to the best advantage, i.e.
the regions of the body and the ramus.
The mandibular projection demonstrates the pre-molar region and the inferior
border of the body of the mandible. It provides much broader coverage than is available
with periapical projections.
Mandibular ramus projection:
This projection will give a view of the ramus from the mandibular angle to the
condyle. It is often very useful for examining the third molar region of both the maxilla
Radiographic examination of the skull requires patience, attention to detail
and practice to produce satisfactory results.
Postero anterior projections;
The straight postero anterior projection is so named because the x-ray
beam passes in a postero anterior direction through the skull. It is used to examine the
skull for the presence of disease, trauma, or developmental abnormalities. It also
provides a good record to detect progressive changes in the medio lateral dimension of
Lateral skull projections:
The lateral skull projection is used to survey the skull and
facial bones for evidence of trauma, disease or developmental abnormality. This view
reveals the nasopharyngeal soft tissues,
paranasal sinuses and hard palate. In
orthodontics it is used to assess facial growth and in oral surgery and prosthetics it is
often used to establish pre-treatment and post-treatment.
Water’s projection also called the occipitomental projection, is a variation of
the PA view. It is particularly useful for evaluation of the maxillary sinuses. In addition
it demonstrates the frontal and ethmoidal sinuses, the orbit, the fronto zygomatic suture
and the nasal cavity. The projection also demonstrates the position of the coronoid
process of the mandible between the maxilla and the zygomatic arch.
The reverse-towne projection is used when fracture of the condylar neck and
displacement of the condyle are suspected. This projection also reveals the
posterolateral wall of the maxillary antrum.
The submentovertex projection (also called the base or full axial
projection) can be used to demonstrate the base of the skull. It also reveals the position
and orientation of the condyles, the sphenoid sinus, and the curvature of the mandible,
the lateral wall of the maxillary sinuses and displacement of a fractured zygomatic arch.
The medial and lateral pterygoid plates and foramina in the base of the skull are often
seen to advantage.
Panoramic radiography (also called pantomography or rotational
radiography) is a radiographic procedure that produces a single image of the facial
structure, including both maxillary and mandibular arches and their supporting
The principal advantages of panoramic radiograph are.
1. The broad anatomic region imaged.
2. The relatively low patient radiation dose.
3. The relative convenience, ease and speed. With which the
procedure may be performed.
4. The fact that the procedure may be performed on patients
who are unable to open their mouth.
The panoramic radiograph is most often used when broad coverage of the
jaws is desirable, for e.g., in edentulous patients, patients who do not tolerate intra oral
procedures well or patients with large known or suspected pathoses.
The time required to complete the panoramic radiographic examination is quite
short, usually in the range of 3-4 minutes.
The main disadvantage of the panoramic radiograph is that
The resulting image does not resolve the fine anatomic detail that may be
seen on intraoral periapical radiographs.
Other problems associated with panoramic radiographs are magnification,
geometric distortion and over lapped images of teeth, especially in the premolar region.
In addition, objects whose recognition may be important for the
interpretation of the radiographs may be situated outside of the section or
plane of focus (called the focal trough) resulting in their images being
distorted or obscured on the resultant radiographs.
The cost of panoramic dental x-ray machine is approximately 2-4 times that
of an intraoral x-ray machine.
In spite of these disadvantages, experience indicates that panoramic radiographs can
be very useful in assisting the dentist in a number of specific diagnostic tasks.
These indications include:
The evaluation of trauma, third molars, extensive or unique pathoses and
their associated surgical procedures.
The evaluation of tooth developed, especially mixed dentition analysis.
The evaluation developmental anomalies.
Panoramic films are not suitable for diagnostic examination require high image
resolution for example:
The detection of early alveolar bone
The detection of incipient dental caries.
The analysis of trabecular bone changes associated with early periapical
Although during the past 25 years there has been an explosion in the
variety of techniques for medical imaging that are capable of giving much additional
helpful information, conventional radiography is likely to prevail in the foreseeable
The new technique applicable to dentistry is as follows.
Tomography (also called body section radiography) is a process by
which an image of a layer within the body is produced while the images of structures
above and below that layer are made invisible by flurring.
In dental radiology, tomography is frequently used to visualize the TMJ.
Use of tomography allows the condyle to be oriented for an accurate lateral or AP view
with minimal superimposition, of adjacent structures. Tomographic views are also used
to examine other facial structures.
Computed tomography was introduced in the mid 1970’s
Computed tomographic system are often referred to as computed tomography (CT) or
computed axial tomography 9CAT) scanners. CT Scanners produce digital data
measuring the extent of x-ray transmission through an object. This numerical
information may be transformed into a density scale and used to generate or reconstruct
a visual image.
CT provides greater geometric precision.
The sensitivity of the detector combined with the power of the computer
makes it possible to discriminate between objects with small differences
in density such as blood and fat or blood and CSF.
The sensitivity of the detectors is so great that a large amount of
information can be accumulated with relatively small amount of radiation.
CT is of particular value in dealing with certain types of pathologic conditions that
occurs in and around the face.
In paranasal sinuses it was found that CT scanning was better able to detect
extension of disease into the orbit or the base of the skull than either conventional
radiography or pluridirectional tomography.
Further more, when lesions could be identified as malignant, the precise
localization that was obtainable with CT scanning proved to be the most accurate means
of deciding whether surgery or radiation therapy was the treatment choice. In case of
trauma, multidirectional tomography is of value in identifying facial fractures.
However, injuries to the midface are commonly associates with subdural or epidural
hematomas, which can be demonstrated by CT scanning but which elude conventional
types of tomography.
CT scan is valuable in defining the soft tissue margins of carcinomas in the
maxilla. CT scanning has also proved to be valuable in scanning the salivary glands,
particularly after the injection of contrast agents. In some instances it has been possible
to identify masses that lay adjacent to the parotid gland and could not be recognized
during routine sialography. Intraosseus lesions are best evaluated by routine
radiographic approaches, but the potential contribution of CT scanning should be kept
in mind when there are questions about potential soft tissue associations with bony
Tomosynthesis is a radiographic technique used to generate an image of a slice
or plane through an object. It is accomplished by making multiple images of the object
from different angles. These images may be superimposed to produce a tomosynthetic
reconstruction of the desired plane.
Image reconstruction may be accomplished by super imposing radiography,
using mirrors or various electronic means including computers. These means have been
found to provide clinically interesting view of structures in 3 dimensions made from
conventional dental radiographs.
MAGNETIC RESONANCE IMAGING: (M R I)
The MRI system appears to have the potential of producing images that are
superior in contrast discriminations and for detecting and diagnosing lesions not
revealed by a CT image is characterized by just one parameter, the x-ray alteration coefficient of the tissue, but MR image is influenced by 3 different tissue properties.
1. Density of the participating nuclei
2. The time it requires for them to realign with the magnetic field
3. The effects of the interactions of the participating nuclei’s magnetic moments on
4. By varying the technique it is possible to emphasize any one of these MRI
parameters over other two, so that image contrasts can be tailored to a particular
MRI appears to have the potential discriminate between normal and
Measure blood flow even in the capillary beds.
Performs chemical analysis in the body to provide information in the
processes occurring inside the cells and even moniter intracellular pH.
It is a technique for the x-ray examination of joint following the
introduction of a contrast medium into the joint space.
Although the diagnostic injection of the TMJ was initiated during the late
1940’s, it has only been during the past 20 years that the recognition of the technique’s
useful has been growing and its practice pursued.
In disorders of the joint resulting from disk displacement and or
perforation and other pathologic changes in the intra-articular soft tissues, arthrography
may be the main source of information other than surgery.
The patient’s who are selected for arthrographic evaluation are those whose complaints
are persisted and for whose conservative treatment has failed to provide relief, such as
those with pain, tenderness and symptoms of dysfunction like locking and clicking with
pain and limited opening. It is most diagnostically revealing in those cases in which no
bony change is apparent.
In general the greatest value of the arthogram is to confirm a clinical
impression. The technique is performed under sterile conditioning and is not without
The joint space is small so that meticulous placement of the needle and the
introduction of the contrast medium must be monitored fluoroscopically. Also the
contrast agent remains in plane from a very short time so that arthograms must be made
within 10 minutes.
To further complicate the procedure the arthrographic examination requires
that several tomographs of the joint be made during the limited period to demonstrate
the movement of the intra articular soft tissues during various stages of function.
Although arthrography is relatively safe and effective, the procedure is
contraindicated if the patient is hypersensitive to one of the contrast agent’s component
or if there is a local skin or periarticular joint infection.
It is a radiographic procedure that is a useful diagnostic adjunct for that
detection and monitoring of salivary gland disease. This technique is used to examine
the ductal and acinar systems of the major salivary glands.
The glands are cannulated and filled with a radio opaque contrast agent to
make them visible on radiographs.
The procedure will reveal the location and integrity of the salivary glands, thus
indicating the presence of disease that changes internal architecture.
CHEST RADIOGRAPH AND ELECTRO CARDIOGRAM (E C G)
A chest radiograph and an ECG should be ordered for any patient with a
history of pulmonary of cardiovascular disease, especially if he has not been examined
with in the last 6 months. In addition, symptoms or physical findings may indicate that
these tests should be obtained. Any patient over age 40 should have a chest radiograph
and an ECG annually.
MEDICAL LABORATORY STUDIES:
Indicated tests are performed after the
history has been secured and the physical examination has been completed. Frequently
values obtained from such tests are helpful in establishing the final diagnosis.
Complete blood count:
The complete blood count usually includes tests that have the potential of
revealing a vast number of abnormal systemic conditions. Some of which may be
related to oral lesions.
A stained smear of a blood sample can be prepared for differential leukocyte
counts and for an examination of the erythrocyte and platelets morphology. Alterations
in the size, shape, and Hb content of erythrocytes can be determined and an estimate of
the platelet numbers be made from the microscopic examination of the smear.
Total leukocyte count:
Leukocytes are important in the defense of the body against invading micro
organisms, since they combat most harmful bacteria.
An increase (leukocytosis) is the most common alteration in the count and is
usually interpreted to indicate the presence of a systemic infection It may also be
observed after general anesthesia and in such conditions as emotional upsets and blood
A decrease in no of leukocytes (leucopenia) may also be seen in blood dyscrasias,
over whelming infection and drug and chemical toxicoses.
Differential leukocyte count:
The several types of leukocytes can be identified microscopically. Each of these
cell types normally makes up an average percentage of the total leukocyte count..
The normal range of the count is 500/ml to 10000/ml
The normal percentage of the individual leukocyte in the differential count range as
Neutrophils 54% to62%
Lymphocytes 25% to 33%
Monocytes 3% to 7%
Eosinophils 1% to 3%
Basophils 0% to 1%
It is often helpful to know whether the proportions of these cells in the blood have
changed, in as much as the changes may be indicative of particular group of diseases.
For instance, neutrophils are increased in most bacterial infections.
Eosinophils may be increased in parasitic infection and allergic conditions.
Basophils may be increased in some blood dyscrasias.
Lymphocytes may be increased in measles and in most chronic bacterial
Monocytes may be increased during recovery from severe infections, Hodgkin’s
disease and lipid storage disease.
It is recognized that a leukocytosis caused only by a moderate increase in
the neutrophil fraction indicates an acute bacterial infection.
On the other hand, a leukocytosis accompanied by a moderate increase in the
lymphocyte fraction (lymphocytosis) suggests a chronic infection, either bacterial or
A leukocytosis of over 20,000 ml strongly suggests the presence of leukemia.
The number of platelets normally ranges between 15000/ml and 450000
ml of blood. Mature effective platelets are necessary for co-agulation of the blood and
for cloth retraction to be effective. Consequently when platelets count is low, the
bleeding time can be expected to be prolonged. On the other hand, a platelet count
provides information only about the quantity of platelets in the blood, and haemostatic
disturbances may be infact be caused by a defect in the quantity of the platelets.
Although there are a number of blood disorders of dental interest in which the
platelets count is normal, and increased may be the result of Polycythemia Vera,
fracture, hemolytic anemia, or chronic myelocytic leukemia;
A decrease may be the result of thrombocytopenic purpura, pernicious
anemia, aplastic anemic or acute and chronic leukemia.
Hb is the essential oxygen carrier of the blood, and in adults the normal
range is 12 to 18 g/dl women usually have slightly lower values than men. The hb is
decrease in hemorrhage and anemias and is increased in hemoconcentration (increase in
the erythrocyte content of the blood or decrease in the water content of the blood)
polycythemia is an example of an excess of erythrocytes in the blood.
The hemoglobin concentration and erythrocyte count do not always rise or fall
equally. This fact is often important in the differential diagnosis of anemias.
In iron deficiency (microcytic) anemia the Hb concentration is reduced more than the
erythrocyte count and in pernicious anemia the erythrocyte count is reduced more than
the Hb concentration.
Most elective general anesthetics are not administered to patients with a
hemoglobin concentration of less then 10 g/dl
This test measures the percentage volume occupied by the packed
erythrocytes in relation to the total volume of the blood. The normal range is 40 % to
54% in men and 37% to 47% in women.
The percentage is raised in polycythemia, oxygen deficiency states and
dehydration. In the usual dental setting the hematocrit, the Hb concentration and the
erythrocyte count are used as measures of the oxygen carrying capacity of the blood.
Consequently only one of these tests is usually ordered.
The BT is the measure of the ability of capillary blood vessels to contract
or retract after cutting and to retain a plug of coagulated blood. Thus, when there is an
injury to bone or an injury in tissue with a great amount of collagen, they may be
prolonged bleeding time since there will be a lack of soft tissue into which the blood
vessel can retract.
In general, the time required bleeding to stop is related to the manner in
which the wound was produced, the caliber of the vessel involved, the amount of tissue
damage adjacent to the wound, the systemic blood pressure.
The upper limit of the normal bleeding time determined by the Ivy technique is 4
mins. Duke method 7 to 8 mins are regarded as normal.
The potential of the blood to form a mature coagulation within an
appropriate time frame indicates a normal clotting time.
A coagulation time of 6 to 17 mins determined by the white method is considered
Abnormal values from this test may be inductive of number of blood dyscrasias such as
Deficiencies of antihemophilic globulin, plasma thromboplastin component or
plasma thromboplastin antecedents.
The patient test is an indirect measure of the capacity of the blood to clot. In
the clotting process Prothrombin level is converted to thrombin. When the prothrombin
level of the blood is lower than normal, the clotting tendency of the blood within the
blood vessels is believed to be diminished.
An abnormal patient may be inductive of deficiencies in the following blood
factors. Prothrombin, fibrinogen and stable and labile factors. The prothrombin content
of the blood is lowered in liver diseases, hypoprothrombinemia of infants and vit K def
and after therapy with some drugs like dicumerol.
The normal PT is usually reported as 11 to 13 seconds with a normal control of
Partial thromboplastin time (PTT):
Since the PT test bypasses the intrinsic clotting system and the whole bloodclotting time is insensitive to all but gross deficiencies of co-agulation, there is need for
a simple procedure to detect mild to moderate deficiencies of the intrinsic clotting
When a crude phospholipids test extract (partial thromboplastin) is mixed with
plasma, the mixture normally clots in 60 to 90 sec as compared with the normal patient
of 11 to 13 sec. A patient with factor VII deficiency will have a normal thromboplastin
time (PTT) and a prolonged PT. Another use for the PTT is to demonstrate circulating
This test is performed to discover whether there is a disorder in glucose
metabolism. The glucose concentration in whole blood is normally between 5o and
150 /dl, 10% to 15% higher in plasma.
An increase in the blood glucose levels is found in
chronic liver disorder
over activity of number of the endocrine glands
In mild diabetes there may be a normal glucose levels, so if diabetes is suspected, more
sensitive tests, such as the glucose tolerance test, must be performed.
Blood urea nitrogen (BUN):
The bun test is a test of kidney function. ordinarily the kidneys readily excrete
urea, the end product of protein metabolism. Thus the blood urea concentration is
usually fairly low.
In certain kidney disorders, however the ability of the kidneys to excrete urea may be
impaired and the concentration of urea nitrogen in the blood then increases.
Normal range for urea nitrogen is 9 to 20 mg/dl of blood.
Serum creatinine and the ratio of BUN to creatinine (normally 10:1) offer a more
reliable assessment of renal status.
pH of the urine:
The kidneys maintain the blood at the correct pH by excreting into the urine
any excess ions that might alter the pH of the blood.
The urinary pH therefore varies widely, and changes do not indicate an
abnormality. The kidney may excrete urine with a pH value as low as 4.5 and as high as
8.2 under extreme conditions.
The mean pH of the normal mixed 24 hours specimen, however is about 6
Specific gravity of the urine
The specific gravity urine test measures the ability of the kidneys to
concentrate and dilute urine and thus gives an indication of their functional capacity.
The specific gravity of urine normally varies between 1.015 and 1.025 but is subject to
wide fluctuations under various conditions.
Ordinarily the specific gravity rises when the fluid intake is low and falls
when the intake is high.
Sugar in the urine:
In some disorders sugar is found in the urine. This occurs most often in
diabetes mellitus, but may also occur in other metabolic disorders of varying
Albumin in the urine:
Ordinarily the albumin in the blood does not pass through the glomerular walls
into the urine. In several conditions, however, such as kidney disease, hypertension,
severe heart failure, and drug toxicosis, albumin appears in the urine.
Acetone in the urine:
It is an important in the diagnosis of ketosis, a type of acidosis produced by faulty
Normally there is no acetone in the urine. In a condition such as diabetes, however,
sugar is not utilized properly and an excess of body fat is metabolized. The fatty acids
are broken down into acetone acetic acid and beta-hydroxybutyric acid. They are
converted to acetone which is then excreted by the kidneys. Acetone in the urine
indicates a general disorder of metabolism. The patient may exhibit symptoms of
depression of CNS.
“THE BEST SURGEON IS A CLINICAL PATHOLOGIST WHO PERFORMS
It is obvious that the surgeon who appreciates the
fundamental morphologic and biochemical changes in the tissues of his patients is likely
to devise and perform better operations. Through the medium of biopsy, the donor in
clinical practice has an opportunity to learn and relearn important basic scientific facts.
This he can gain a better understanding of the pathosis of the soft and hard tissue by
establishing a 2- way communication with his pathologists and by personally reviewing
the microscopic findings.
Obtaining a biopsy specimen of an area in the oral cavity may be carried
out under regional block anesthesia, with appropriate sedation, in the outpatient setting.
There will be occasions, however, when the location, nature and extend of the lesion
require the hospitalization of the patient for the biopsy.
Although the biopsy procedures may be divided into a number of types, they are either
excisional or incisional in nature.
The excisional biopsy:
It is accomplished by removing the entire lesion and submitting it for
microscopic examination. This is the preferable approach in most cases, since only one
surgical experience is necessitated and the diagnosis and treatment occur without a
delay. Thus saving time and recurrence for all concerned
The incisional biopsy:
It implies the acquisition and presentation of a representative section from the
lesion. The incisional biopsy is usually completes with a scalpel, although punch,
aspiration and needle technique are also employed.
The representative section must include, if possible, the junction with the surrounding
The needle biopsy:
It is a suitable method of obtaining representative tissue especially when the
lesion is deep to the surface.
This technique is useful to diagnosis lesion of lymph nodes and salivary and
thyroid glands as well as other soft tissue and bony lesion.
If the diagnosis must be available immediately, however frozen section may be
obtained. In the frozen section procedure the fresh specimen is subjected to extremely
low temp and the sections are prepared and read with in 30 mins.
Smear techniques have been immensely successful as a screening procedure for
diseases. Oral Exfoliative cytology is of limited use and should be considered only as a
screening procedure. Furthermore, it is not as accurate for identifying malignant lesions
as is the biopsy.
Toluidine blue staining:
In the late 1960 s and early 1970 s the toluidine blue staining technique has been
recommended for the routine screening of suspicious oral lesion that may be malignant.
These are important limitations to the accuracy of the technique, however, the toluidine
blue dye stains the acidic groups (phosphoric, sulfuric and carboxylic) present in normal
and inflamed tissues as well as in benign and malignant tumors so that the results of the
staining are equivocal.
MICROBILOGICAL DIAGNOSTIC TECHNIQUES:
The isolation, identification, and susceptibility
testing of micro organism associated with infection are important components in
determination of the diagnosis and appropriate therapy for many infectious diseases.
This testing usually is accomplished by microscopic examination culture of
specimen’s representative of the site of infection.
The infectious disease associated with oral and maxillofacial region have unique
microbiological feature because of the abundance and variety of microorganisms in this
Culture detection of a specific micro organism or the determination of an organism’s
significance from culture often is complicated. Because of the large number of flora
in the oral cavity, the risk of specimen contamination with bacteria unrelated to
infection is increased.
Thus the careful collection of appropriate specimens is extremely important in the
accurate diagnosis of infections from this region.
In general, the role of the microbiology laboratory is to aid the clinician in the
diagnosis of infectious diseases. Although cultures may require several days to
several weeks for completion depending on the organism, the results or rapid tests
such as the gram strain and non cultural methods are available to guide the initiation
of the therapy.
Specific acquisition and transport:
The result obtained from microbiological examination and culture depends on the
care observed in specimen collection.
Because the optimal site and time of collection have an important influence on the
usefulness from a site representative of infection.
All specimens for microbiological examination and cellular should be transported
to the laboratory promptly because they are subjective to deterioration and overgrowth
Extremes of temperature, delay, dehydration and the presence of nutrients in body
fluids result in the death of more fastidious organisms and overgrowth of rapidly
growing but less important organisms, thus producing misleading reports.
The optimum time for specimen transport to the laboratory is less than 2 hours.
Direct methods of specimen examination:
The initial step in the processing of most clinical material is microscopic
examination of the specimen.
Much importance can be obtained from smear preparations. A gram-stained direct
smear provides the clinician with rapid information regarding the quality of the
specimen and the bacterial morphotypes present.
Similarly, fungal stains, wet preparations and acid fast stains provide rapid
evidence of fungal and mycobacterial infection, respectively.
In addition to staining technique, direct detection of microbial antigens or
nucleic acids provides rapid evidence of the causative agents of disease and may be the
most reliable detection method for microorganism that do not grow well in culture.
Preparation and staining: Care should be taken to prepare a smear that is representative
of the specimen and do no too thick. Thick smears are often uninterpretable and material
has a tendency to be off the slide during staining.
Methanol is the preferred method of specimen fixation before staining because
heat fixation may distort the morphological appearance heat fixation may distort the
morphological appearance of cells and bacteria. The use of 50% mixture of acetone and
alcohol provides an optimal decolorization.
The gram stain differentiates bacteria based on their ability ( gram positive) or
inability ( gram –ve) to retain the crystal violet dye and their size and shape of gram _ve
organism, micrococcus, staphylococci, streptococci appears as spherical gram +ve
Micrococci and staphylococci are often arranged in tetrads or appear as irregular grape
like clusters. Streptococci are often arranged in pairs or chains. Streptococcus
pneumoniae displays characteristic lancet-shaped cocci most often in pairs.
Gram –ve cocci occurs singly (veillonelle) or in pairs (neisseria, moraxella,
acinetobacter). The gram -ve rods constitute a large number of pathogenic species but can
be subdivided into four categories.
The largest gram –ve rods are represented by the family enterobacteriaceae.
These enteric bacteria often display bipolar staining with intensification of safranin
staining at the poles of cell with a less intense staining in the centre of the cell.
Gram –ve rods with a thinner, more uniform staining appearance are often of the
genus pseudomonas or a related genre.
Small, coccobacillary gram 0ve rods represents bacteroides, haemophilus and
Long filamentous and pleomorphic forms may be seen depending on the specimen
The gram stain is particularly helpful in providing presumptive
evidence of the presence of anaerobes because many anaerobic organism display
distinctive features on microscopic examination.
The presence of small, faint staining gram –ve rods is often indicative of
organisms such as bacteroides, fusobacterium, prevolette and porphyromonas. Long,
thin gram –ve rods with pointed ends are suggestive of fuso bacterium nucleatum and
large box car shaped gram +ve rods are suggestive of clostridium.
Brown-Brenn tissue gram stain:
This method is used exclusively on histological sections of tissue to demonstrate the
same gram =ve and gram –ve characteristic shown with the gram method. The
identification of gram –ve organism is often difficult in these preparations because of
their confusion with tissue artifacts
All specimens of sufficient quality should be examined microscopically if fungi are
Fungal elements including yeast, pseudo hyphae, and true hyphae may be visualized
using a 10% potassium hydroxide preparation or any of the following stains:
Periodic acid-Schiff (PAS)
PAS stain is used by microbiologist and pathologist to demonstrate fungi in chemical
specimens and histological sections.
Acid fast stains:
Acid fast smear play an important role in the early diagnosis of mycobacterial
infection because of the relatively slow growth rate of mycobacterium in culture. Acidfast organisms are difficult to stain because of the high lipid content of their cell walls.
Acid fast stains take advantage of mycobacterium’s retention of basic fuschin dyes or
fluorochrome stains after decolorization with an acid-alcohol solution.
Wet preparations and dark field microscopy:
Wet preparations may be prepared from exudates, scrapings, fluid and tissue. The
addition of 10 % potassium hydroxide to the specimen dissolves mucous and cellular
material, thus facilitating visualization of fungal structure.
Dark field microscopy is a modification of the wet preparation in which the
specimen is examined using a microscope with a dark field condenser.
Dark field examination of specimens by dark field microscopy is most frequently
used for the detection of treponema palladium in suspected syphilitic lesions.
Direct detection of microbial antigens and nucleic acid:
Advances in immunological and molecular techniques have provided
clinicians with a variety of assays to diagnosis infections diseases more rapidly and
These assays also provide the ability to detect microorganism that grow slowly in
culture or not al all.
These techniques includes
Deoxyribonucleic acid (DNA) probes
Most recently nucleic amplification.
Specimen processing, isolation and identification of microorganism:
Although direct methods of examination provides rapid results of the presence or
absence of microorganisms, the isolation and identification of viable organism, is still
considered the “ GOLD STANDARD” for the diagnosis of most pathologist.
Culturing offers the advantages of providing exact organism identification and the
ability to perform antimicrobial susceptibility testing on the isolate.
Although virus and Chlamydia require the use of living tissue cells for growth, the
isolation of most organisms is accomplanished by using synthetic or semi synthetic
A combination of enriched, selective and differential media is used for the
isolation and presumptive identification of bacteria from clinical samples.
The basic components of these media include digests of casein or plant and animal
proteins and salts to provide an isotonic and buffered environment. Agar is added to
solidify the media.
The addition of blood, carbohydrates or other factors to the media enhances the
growth of some bacteria (enriched media) and provides an environment in which the
growth or metabolic characteristics of certain organisms can be differentiated from
The addition of dyes and antibiotics to media provides inhibitory properties that
permit the selective detection of certain pathogens (selective media).
Enriched media such as sheep blood and chocolate agar provides the nutrients necessary
to cultivate a wide variety of bacteria.
Differential media such as McConkey and eosinmethylene blue agar is used
extensively because of their carbohydrate fermentation.
Viruses and Chlamydia species:
Viruses and Chlamydia is obligate intracellular organism and require
living cells for growth and reproduction.
Virus can be cultivated in cell cultures, embryonated eggs and laboratory animals
Antimicrobial susceptibility testing
The choice of the appropriate antimicrobial agents for treatment of an
infection depends on several important factors.
First, antimicrobial therapy must be directed as specifically as possible against
the infecting organism.
Therefore before the isolation of these organisms, the clinician must consider the
organism likely to be found at the site of infection.
Second, an antimicrobial agent must be chosen that will exhibit appropriate
pharmacological properties and activity against the target organisms.
Third, host factors such as age, renal and hepatic function, site of infection and
previous adverse drugs reactions must be evaluated for their influence on the
choice of antimicrobial agents.
The use of empirical therapy often accompanies but should not severe as a replacement
for necessary surgical therapy.
Surgical intervention often augments empirical therapy because the disadvantage of
abscess cavities and the removal of necrotic tissue and sequestra (bone and teeth) are
necessary for effective action of the antimicrobial at the site of infection.
METHODS FOR DETECTION OF HBSAG AND ANTI HBS :
The term “viral hepatitis “ refers to a primary infection of the liver by hepatitis
virus type A or type B or by other hepatic viruses as yet not characterized and referred
to as “ non- A, non-B hepatic virus.” Hepatitis may occur incidentally during the course
of infection with many other viruses.
One type occurs either sporadically or in epidemics affecting mainly children and
young adults and apparently transmitted by the faecal-oral route this was called
infective or infectious hepatitis. It is now known as type-A hepatitis.
Second type of viral hepatitis is transmitted mainly by inoculation and was originally
observed in persons receiving serum inoculation or blood transfusion. this has been
known by several names such as homologus serum jaundice or serum hepatitis, it is
currently called type B hepatitis.
REVERSED PASSIVE LATEX AGGLUTIN
LABORATORY DIAGNOSIS OF HIV INFECTION:
Laboratory procedures for diagnosis of HIV infection include tests for
immunodeficiency as well as specific tests for HIV.
1. The following parameters help to establish the immunodeficiency in HIV
2. Total leukocyte and lymphocyte count to demonstrate leucopenia and a
lymphocyte count usually below 2000/c.mm\
3. T cell subset assays. Absolute T4 cell count will be usually less than 200/c.
mm. T4:T8 cell ratio is reversed.
4. Platelet count will show thrombocytopenia.
5. Raised IgG and IgA levels
6. Diminished CMI as indicated by skin tests.
Specific test for HIV infection:
These include demonstration of HIV antigens and antibodies and isolation
of the virus.
1. Antigen detection
2. Virus isolation
3. Antibody detection
2. fujirebio agglutination
3. Karpa’a test
4. Indirect immunofluorescence
5. Western blot test (confirmatory test).
ELISA TEST: screening test.
Elisa is simple and relatively inexpensive but false positive reactions are not
uncommon, particularly with sera containing rheumatoid factor or anti-lymphocyte.
Direct solid phase Elisa is the method most commonly used. The antigen
obtained from HIV grown in continuous T lymphocyte cell line or by recombinant
techniques is coated on microtitre wells or other suitable solid surface.
Western blot test: confirmatory test
In this test HIV proteins separated according to their electro-phorectic
mobility by polyacrylamite gel electrophoresis are blotted on to strips of nitrocellulose
paper. These strips are reacted with test sera and then with enzyme conjugated anti
human globulin. Suitable substrate is then added which produces a prominent colour
band where specific antibody has reacted with the separated viral protein.