Anchorage in orthodontic treatment

ANCHORAGE IN

ORTHODONTICS

Maryam ArbabHouse OfficerDepartment Of OrthodonticsSBDC

DEFINITION

Anchorage in orthodontics is defined as the resistance to displacement offered by an anatomic unit for the purpose of tooth

movement

CLASSIFICATIONAccording to force application

simple stationary reciprocal

The manner & application of force is such that it tends to change the axial inclination of teeth that forms the anchorage unit

The manner & application of

force tends to displace the

anchorage unit bodily in the

plane of space in which the force is

being applied

The resistance offered by two malposed units

when the dissipation of

equal &opposite force move each unit towards a

normal occlusion

Simple anchorage : Removable appliance incorporating a screw for buccal movement of a platally placed premolar

Stationary anchorage

1.Correction of midline diastema using elastics.Reciprocal

anchorage: Midline diastema closure

3. Finger Springs used to close amidline diastema.

2. Arch expansion using a removable appliance incorporating a coffin spring.

According to Jaws Involved :1. Intra-maxillary

The anchor units and teeth to be moved are situated in same arch.

2. Inter-maxillary

The anchor units and teeth to be moved are situated in opposite arches

Example

CLASS II ELASTICS CLASS III ELASTICS

According to number

Single or Primary Compound Reinforced

or Multiple

Resistance provided by single tooth OR a single tooth with more alveolar support is used to move one with lesser alveolar support.

More than one tooth in anchorage unit OR anchorage provided by more than one tooth with more support to move a tooth with less support.

More than one type of resistance unit is utilized. E.g: To augment the intra-oral anchorage, extraoral anchorage, TPA,& lingual arch is used

single compound

reinforced

Lingual ArchTranspalatal Arch

Extra-Oral Anchorages

According to Site :

Intra - oral Extra oral Muscular

The intraoral sources of anchorage include the:Soft tissuesTeethBone (palatal vault)Basal jaw bone

The extraoral sources of anchorage include the:Occipital boneBack of the neckcranium & face

Perioral musculature

intraoralExtra oral : Occipital headgear

Musculature ( lip bumper)

PRINCIPLES OF ANCHORAGE When one teeth moves, other serves as an

anchor units depending upon : - root size - number of root - root inclination

Increase anchorage value by restricting anchored teeth to bodily movement

Do not use heavy force which leads to hyalinization

ANCHORAGE PLANNING Anchorage requirements depends on a

number of factors, listed as :

Number of teeth being moved : Greater number of teeth being moved ,

greater is the demand of anchorage

Type of teeth being moved : Movement of anterior teeth provides lesser

strain , compared to multirooted tooth

Type Of Tooth Movement : Bodily movement applies greater strain

on anchorage compared to controlled tipping tooth movements

Duration of Treatment : Prolonged duration of treatment places

undue strain on the anchorage

Occlusal Interlock : A good buccal occlusion may act to resist

tooth movement

ANCHORAGE DEMAND Anchorage demand can be of three types :-

Maximum anchorage

Moderate anchorage

Minimum anchorage

Not more than 1/4th of the extraction space should be lost by forward movement of anchor teeth

Anchor teeth can be permitted to move forward into 1/4th to ½ of extraction space

More than half extraction space can be lost by anchor teeth moving mesially

ANCHORAGE LOSS Certain amount of unwanted movement of the anchor teeth

invariably occuring during orthodontic treatment .

Anchorage loss can occur in all three planes:

Sagittal plane : - mesial movement of molars - proclination of anterior teeth

Vertical plane : - extrusion of molars - bite deepening due to anterior extrusion

Transverse plane : - buccal flaring due to over expanded arch

form - lingual dumping of molars

METHODS TO CONTROL ANCHORAGE

1. Reinforcement :- Addition of teeth to anchorage unit Reinforcement may also include forces

derived from structures outside the mouth

2. Subdivision of desired movement :- Pit the resistance of a group of teeth

against the movement of a single tooth

3. Tipping / Uprighting :- Tip the teeth and then upright them rather than

moving them bodily

4. Friction & Anchorage control strategies :- one step space closure with frictionless

appliance

Two step space closure sliding the canine along the arch wire , then retracting the incisors

Two step space closure , tipping the ant. segment with some friction and then uprighting the tipped teeth

5. Skeletal Anchorage :- Temporary skeletal anchorage is derived

from: implants miniplates

Temporary Anchorage Devices (TADs)

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