Tooth movement during orthodontic therapy is brought about by forces generated by the active components of an orthodontic appliance. The force used to move teeth is derived from certain anatomic areas which act as anchors.  Anchorage is defined as the resistance to unwanted tooth movement or as a desired reaction of posterior teeth to space closure mechanotherapy ⁽¹⁾

Graber has defined anchorage in orthodontics as the nature and degree of resistance to displacement offered by an anatomic unit for the purpose of effecting tooth movement.

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

According to Newton’s third law of motion , for every action there is an equal and opposite reaction. In accordance with this law , the forces used to move teeth may induce an equal and opposite force on the anchorage unit , tending to cause their movement.

Anchorage loss therefore is a reciprocal reaction that could obstruct the success of orthodontic treatment by complicating the anteroposterior correction of the malocclusion and possibly detracting from facial esthetics. ⁽²⁾

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