COMPARATIVE EVALUATION OF ANCHORAGE LOSS BETWEEN ACTIVE TIE BACKS AND COIL SPRINGS DURING ENMASSE RETRACTION IN BIMAXILLARY PROTRUSION CASES

Tooth movement during orthodontic therapy isbrought about by forces generated by the active components of an orthodonticappliance. The force used to move teeth is derived from certain anatomic areaswhich act as anchors.  Anchorage isdefined as the resistance to unwanted tooth movement or as a desired reactionof posterior teeth to space closure mechanotherapy (1)

Graberhas defined anchorage in orthodontics as the nature and degree of resistance todisplacement offered by an anatomic unit for the purpose of effecting toothmovement.

Dependingon the requirement, it can be classified as maximum anchorage(type A) ,moderate anchorage (type B) and minimum anchorage units ( type C). (1)

Accordingto Newton’s third law of motion , for every action there is an equal andopposite reaction. In accordance with this law , the forces used to move teethmay induce an equal and opposite force on the anchorage unit , tending to causetheir movement.

Anchorageloss therefore is a reciprocal reaction that could obstruct the success oforthodontic treatment by complicating the anteroposterior correction of themalocclusion and possibly detracting from facial esthetics. (2)

Alongthe course of this study we intend to measure the anchorage loss in themaxillary first molar (anchorage unit) in bimaxillary cases where en-masseanterior retraction is done using conventional retraction techniques.