ANCHORAGE IN ORTHODONTICS
ANCHORAGE IN ORTHODONTICSMaryam ArbabHouse OfficerDepartment Of OrthodonticsSBDC
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
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
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)