Anchorage Flashcards
Define Anchorage?
- Resistance to unwanted tooth movement
- Resistance of forces generated in reaction to the active component of appliance
- Newton’s Third law of motion - Every action there is an equal and opposites
Principle of Anchorage
1-Differential force theory - Rate of tooth movement is related to force per unit root surface area.
2-Increased roots of tooth increased resistance to tooth movements increased Anchorage value.
3- no relation to surface of tooth.
4- Not linear relationship b/w surface area and tooth movement therefore factor involved - PDL.
5- Large individual variation in rate of tooth movement for particular force applied.
6- Optimal level exists after which if you increase the force there is no increase tooth movement only increase strain on anchor units.
7- Increase number of tooth in anchor unit to increase surface area.
8- Increased anchorage value by restricting anchor teeth to bodily movement.
9- Can view anchorage in terms of space management- Maximise wanted tooth movement and minimise unwanted tooth movement.
10- always consider 3 dimension: AP , lateral , vertical
Loss of Anchorage
- Unwanted tooth movement and space loss.
E.g . Mesial movement of Upper first Permanent molar during premolar extraction space closure
Anchorage loss and Anchorage Burn
- Anchorage loss - Unintentional movement of anchor unit
- Anchorage burn - intentional movement of anchor unit
Space management.
- Maximise wanted tooth movement
- minimise unwanted tooth movement
Types of Anchorage
Intra oral
- Simple Anchorage
- Compound Anchorage
- Stationary anchorage
- Reciprocal anchorage
Simple Anchorage
- 1 tooth against another 1-1
Compound anchorage
- More than 1 tooth in anchor unit
1- Intra maxillary - same arch.-bonding 7s’
2- Inter maxillary- Opposite arches ( class 2-3 elastics traction )
Reciprocal anchorage
- Equal tooth movement towards each other.
- e.g powerchain to close midline diastema
Stationary Anchorage
- Resistance to bodily movement
- force tends to displace Anchorage unit bodily in the plane of space in which force is being applied
-e.g Tads
soft tissue / Bone
- Soft tissue - lip bumper
-Bone - Nance button , palatal vault in URA.
-
Why mandibular teeth have greater anchorage value than maxillary teeth?
- Cortical plates provide increased resistance of tooth movement than cancellous bone.
- Mandibular teeth have greater anchorage value than maxilla teeth.
Extra oral Anchorage
- Anchorage from cranial vault/ basal bones
- Protraction headgear ( reverse headgear)
- Extra oral anchorage
How can you increase Anchorage?
- Band all molars
Factor affecting anchorage
- Type of tooth movement
- Root surface area
- Sk pattern
- Occlusal interdigitation
- Tendency for tooth movement in the arch.
Maxillary teeth have greater tendency for mesial drift.
Reinforcement of Anchorage?
Mechanism
- Increase the number to teeth in anchor unit
- Making movement of anchor teeth more difficult.
- Intermaxillary traction
- Extractions, Extraction pattern
- Implants.
Anchorage reinforcement
Choice of appliances
- Removable appliances- Mucosa and underlying bone , Nance button
- Fixed appliance : Lower friction system
Supplement Anchorage?
- Xtn decision
- Bond/ band 2nd molar to increase anchorage unit
- Extra oral anchorage
- Lingual arch
- Tanspalatal arch / nance button
- inter maxillary elastics
- Fixed with less friction.
- Implants - Tads/ mini screw
What happen when nance wedge in?
-Loss of Anchorage
Why do we use TPA for anchorage
- Use to stop forward movement for 6’s
TAD - Temporary anchorage device
- Important factors with implants
- Quick and easy to insert without damage to adjacent teeth
- Convenient for application of orthodontic forces
- Immediate loading
- Easily removed
- No patient discomfort at insertion or removal
How can we reduce anchorage strain?
- Tip teeth rather than bodily movement
- light force
- low friction - self ligating bracket
- Seperate retraction of individual tooth
- push rather than pull e.g canine retractions
- correct centrelines one tooth at time
Assessment of Anchorage need?
Tooth movement required
- Space required to complete alignment; how much anchor units be allowed to move.
- Bodily or tipping . Increased for bodily movement decreased for tipping movement.
- Angulation of teeth . Increased anchorage required for mseially inclined canine less than upright or distal inclined canine.
- Inclination of teeth - Increased anchorage required for proclined incisors less than Retroclined incisors
What are sources of anchorage ?
- teeth
- implant
- bone
- extra oral
Source of skeletal anchorage devices?
- orthodontic Implants
- palatal implants or onplant
- Zygoma ligature
- mimi plates
- mini screws
AP anchorage
- Extraction choice
What are indication of sufficient anchorage?
- Do you have enough space to move teeth
- normal Overjet
- planned Molar relationship
Mandible teeth has greater Anchorage value than maxillary teeth? Why?
- Cortical plates (mandible) provide greater resistance to tooth movement than Cancellous bone (maxilla).
Anchorage creation
- Distal movement of upper buccal segment with extra oral headgear e.g Nudger appliance
- Implants and distalisation.
- fixed molar correctors e.g pendulum appliance (tends to Procline upper incisors)
- lip bumper to distalise lower molar (tends to Procline LLS).
- Xtn pattern / functional appliance - alter anchorage balance
How can you tell you have sufficient Anchorage?
- Do you have enough space ?
- To move teeth so they are straight.
- Have a normal Overjet between 2-4 mm.
- Planned molar relationship.
Then yes you have sufficient Anchorage
