anchorage
Content
ANCHORAGE IN ORTHODONTICS
P06213 CHAN YEE VAA
Newton’s third Law of Motion
• For every action,there is an equal and opposite reaction
Anchorage
• The nature and degree of resistance to displacement offered by an anatomic unit for the purpose of affecting tooth movement. (Graber) • Anchorage is the site of delivery from which a force is exerted. (White & Gardiner)
Moyer’s classification of anchorage
SITE OF ANCHORAGE
• Intraoral • Extraoral • muscular • Simple • Stationary • Reciprocal • intramaxillary • intermaxillary
MANNER OF FORCE APPLICAION
JAW INVOLVED
NUMBER OF ANCHORAGE UNIT
• Single/Primary • Compound • Multiple or reinfroced anchorage
Classification of Anchorage based on Space Lost
Anchorage
Maximum
Moderate
Minimum
Maximum Anchorage
<1/4th of extraction space can be lost
Moderate Anchorage
1/4th ½ extraction space can be lost
Minimum Anchorage
>1/2 extraction space can be lost
Intraoral Anchorage
Alveolar bone
Teeth
Basal bone
Teeth
1. 2. 3. 4. 5. 6. 7.
Root form Root number and root size Root length Axial inclination of tooth Periodontal status Position of tooth Contact points and intercuspation
Root Form
ROUND FLAT TRIANGULAR
Bicuspids and palatal root of maxillary
molarsMandibular incisors and molars and the buccal roots of maxillary molars Resist movements in the mesio-distal direction but little resistance to movement on the buccal and lingual sides due to thin edges.
Canines and maxillary central and lateral incisors
Resist horizontally directed forces in any direction. Least anchorage.
Maximum resistance
Root number and size
Ratio of PDL of anchorage unit : PDL of area of tooth movement 2:1 in frictionless appliance 4:1 in friction appliance
=
Tripod root arrangement
Tripod roots = molar moved mesially
fused roots = molar rotated mediopalatally
Root Length
Maxillary canines are the most difficult teeth to be moved
Axial Inclination of Tooth
Weaker anchorage
Better anchorage
Periodontal status
Ankylosed tooth
Periodontitis
Intercuspation
Alveolar bone Anchorage
Forces dissipated over a larger bone surface area offer increased anchorage
Maxillary molars have less anchorage than mandibular molars
Why?
• •
thin cortices and trabecular bone More Blood vessels
Cortical Anchorage
Cortical bone are more resistant to resorption compared to medullary bone
L
B
Basal Bone Anchorage
Nance Palatal Button
Lingual Holding Arch
Extraoral anchorage
Headgear (anchorage from occiput and cervical vertebra)
Cervical Headgear Reversed headgear (facemask therapy) (anchorage from forehead and chin)
• Poor patient compliance • Intermittent heavy force
Muscular anchrage
Lip bumper
Simple anchorage
When the manner and application of force is such that it tends to change the axial inclination of the tooth or teeth that form the anchorage unit in the plane of space in which the force is being applied.
Single tooth being pushed labially using an appliance incorporating a screw
Stationary anchorage
• When the manner and application of force tends to displace the anchorage units bodily in the plane of space in which the force is being applied
Reciprocal anchorage
refers to the resistance offered by two malposed units when the dissipation of equal and opposite forces tends to move each unit towards a more normal occlusion.
Diastema closure
Arch expansion using midline screw
Cross elastics to correct molar crossbite
Intramaxillary anchorage
Intermaxillary anchorage
Single/Primary anchorage
• Tooth to be moved is pitted against a tooth with a greater alveolar support area.
• Eg. Molar along with adjacent premolars used to align another molar.
Compound anchorage
• Use of more teeth with greater anchorage potential to move a tooth or group of teeth with lesser support
• Eg. Loop mechanics used to retract anteriors
Reinforced anchorage
• Augmentation of anchorage by various methods: (a) Extraoral appliances (b) Upper anterior inclined plane (c) Transpalatal arch/lingual arch (d) microimplants
Transpalateal arch
lingual arch
oUsed in fixed mechano-therapy oTo prevent mesial movement of anchorage
Anterior Inclined Plane
Microimplants TAD
Types of TAD
According to the exposure of head According to method of placement
Self-Tapping Method
According to the path of insertion
Open Method
Oblique Direction
Closed Method
Self Drilling Method
Perpendicular Direction
According to The Exposure of Head
OPEN METHOD Head exposed Immobile soft tissue (palate/ attached gingival) CLOSED METHOD Head embedded under soft tissue Movable soft tissue
According to The Method of Placement
Self Tapping Method Self Drilling Method
Drill to form tunnel then tap Directly drill the implant into the implant in bone Smaller diameter Microimplant Large diameter microimplant
According to The Path of Insertion
Oblique direction 30-60° to long axis of tooth Narrow inter-radicular bone Perpendicular direction 90° to bone surface Sufficient inter-radicular bone
Sites of placement and Possible Use
•Retraction of Mandibular anterios •Intrusion and distal movement of Mandibular molars
•Retraction of Maxillary anterios •Intrusion of Maxillary buccal teeth
Anchorage planning
1. 2. 3. 4. 5. 6. 7. Number of teeth being moved Type of teeth being moved Type of tooth movement Duration of tooth movement Skeletal pattern Occlusal interlock Periodontal condition
Methods of control anchorage
1. 2. 3. 4. 5. Reinforcement Subdivision of desired movement Tipping/up righting Friction and anchorage control strategies Skeletal anchorage
Any ???
P06213 CHAN YEE VAA
Newton’s third Law of Motion
• For every action,there is an equal and opposite reaction
Anchorage
• The nature and degree of resistance to displacement offered by an anatomic unit for the purpose of affecting tooth movement. (Graber) • Anchorage is the site of delivery from which a force is exerted. (White & Gardiner)
Moyer’s classification of anchorage
SITE OF ANCHORAGE
• Intraoral • Extraoral • muscular • Simple • Stationary • Reciprocal • intramaxillary • intermaxillary
MANNER OF FORCE APPLICAION
JAW INVOLVED
NUMBER OF ANCHORAGE UNIT
• Single/Primary • Compound • Multiple or reinfroced anchorage
Classification of Anchorage based on Space Lost
Anchorage
Maximum
Moderate
Minimum
Maximum Anchorage
<1/4th of extraction space can be lost
Moderate Anchorage
1/4th ½ extraction space can be lost
Minimum Anchorage
>1/2 extraction space can be lost
Intraoral Anchorage
Alveolar bone
Teeth
Basal bone
Teeth
1. 2. 3. 4. 5. 6. 7.
Root form Root number and root size Root length Axial inclination of tooth Periodontal status Position of tooth Contact points and intercuspation
Root Form
ROUND FLAT TRIANGULAR
Bicuspids and palatal root of maxillary
molarsMandibular incisors and molars and the buccal roots of maxillary molars Resist movements in the mesio-distal direction but little resistance to movement on the buccal and lingual sides due to thin edges.
Canines and maxillary central and lateral incisors
Resist horizontally directed forces in any direction. Least anchorage.
Maximum resistance
Root number and size
Ratio of PDL of anchorage unit : PDL of area of tooth movement 2:1 in frictionless appliance 4:1 in friction appliance
=
Tripod root arrangement
Tripod roots = molar moved mesially
fused roots = molar rotated mediopalatally
Root Length
Maxillary canines are the most difficult teeth to be moved
Axial Inclination of Tooth
Weaker anchorage
Better anchorage
Periodontal status
Ankylosed tooth
Periodontitis
Intercuspation
Alveolar bone Anchorage
Forces dissipated over a larger bone surface area offer increased anchorage
Maxillary molars have less anchorage than mandibular molars
Why?
• •
thin cortices and trabecular bone More Blood vessels
Cortical Anchorage
Cortical bone are more resistant to resorption compared to medullary bone
L
B
Basal Bone Anchorage
Nance Palatal Button
Lingual Holding Arch
Extraoral anchorage
Headgear (anchorage from occiput and cervical vertebra)
Cervical Headgear Reversed headgear (facemask therapy) (anchorage from forehead and chin)
• Poor patient compliance • Intermittent heavy force
Muscular anchrage
Lip bumper
Simple anchorage
When the manner and application of force is such that it tends to change the axial inclination of the tooth or teeth that form the anchorage unit in the plane of space in which the force is being applied.
Single tooth being pushed labially using an appliance incorporating a screw
Stationary anchorage
• When the manner and application of force tends to displace the anchorage units bodily in the plane of space in which the force is being applied
Reciprocal anchorage
refers to the resistance offered by two malposed units when the dissipation of equal and opposite forces tends to move each unit towards a more normal occlusion.
Diastema closure
Arch expansion using midline screw
Cross elastics to correct molar crossbite
Intramaxillary anchorage
Intermaxillary anchorage
Single/Primary anchorage
• Tooth to be moved is pitted against a tooth with a greater alveolar support area.
• Eg. Molar along with adjacent premolars used to align another molar.
Compound anchorage
• Use of more teeth with greater anchorage potential to move a tooth or group of teeth with lesser support
• Eg. Loop mechanics used to retract anteriors
Reinforced anchorage
• Augmentation of anchorage by various methods: (a) Extraoral appliances (b) Upper anterior inclined plane (c) Transpalatal arch/lingual arch (d) microimplants
Transpalateal arch
lingual arch
oUsed in fixed mechano-therapy oTo prevent mesial movement of anchorage
Anterior Inclined Plane
Microimplants TAD
Types of TAD
According to the exposure of head According to method of placement
Self-Tapping Method
According to the path of insertion
Open Method
Oblique Direction
Closed Method
Self Drilling Method
Perpendicular Direction
According to The Exposure of Head
OPEN METHOD Head exposed Immobile soft tissue (palate/ attached gingival) CLOSED METHOD Head embedded under soft tissue Movable soft tissue
According to The Method of Placement
Self Tapping Method Self Drilling Method
Drill to form tunnel then tap Directly drill the implant into the implant in bone Smaller diameter Microimplant Large diameter microimplant
According to The Path of Insertion
Oblique direction 30-60° to long axis of tooth Narrow inter-radicular bone Perpendicular direction 90° to bone surface Sufficient inter-radicular bone
Sites of placement and Possible Use
•Retraction of Mandibular anterios •Intrusion and distal movement of Mandibular molars
•Retraction of Maxillary anterios •Intrusion of Maxillary buccal teeth
Anchorage planning
1. 2. 3. 4. 5. 6. 7. Number of teeth being moved Type of teeth being moved Type of tooth movement Duration of tooth movement Skeletal pattern Occlusal interlock Periodontal condition
Methods of control anchorage
1. 2. 3. 4. 5. Reinforcement Subdivision of desired movement Tipping/up righting Friction and anchorage control strategies Skeletal anchorage
Any ???
