Anchorage in orthodontic treatment

ANCHORAGE IN ORTHODONTICS

ANCHORAGE IN ORTHODONTICSMaryam 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 applicationsimplestationaryreciprocalThe manner & application of force is such that it tends to change the axial inclination of teeth that forms the anchorage unitThe 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-maxillaryThe anchor units and teeth to be moved are situated in same arch.

2. Inter-maxillaryThe anchor units and teeth to be moved are situated in opposite arches

ExampleCLASS II ELASTICSCLASS III ELASTICS

According to number Single or PrimaryCompoundReinforced 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

singlecompoundreinforced

Lingual ArchTranspalatal ArchExtra-Oral Anchorages

According to Site :Intra - oralExtra oralMuscularThe 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

intraoral

Extra oral : Occipital headgearMusculature ( lip bumper)

PRINCIPLES OF ANCHORAGEWhen 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 value : quality of tooth to resist movement depends upon root surface areaAnchorage value : density of bone x root surface area14

ANCHORAGE PLANNINGAnchorage 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 DEMANDAnchorage demand can be of three types :-

Maximum anchorage Moderate anchorageMinimum anchorageNot more than 1/4th of the extraction space should be lost by forward movement of anchor teethAnchor teeth can be permitted to move forward into 1/4th to of extraction spaceMore 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 ANCHORAGEReinforcement :-Addition of teeth to anchorage unitReinforcement 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

Tipping / Uprighting :-Tip the teeth and then upright them rather than moving them bodily

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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