Application of mechanical forces to teeth causes tooth movement as a result of the biological responses of the periodontal tissues.¹

Although most of the appliances differ in mode of action, they must ultimately achieve the similar cellular effect like; the resorption and apposition of alveolar bone to produce desired orthodontic tooth movement in the desired direction.²

Local regeneration of tissues involves resorption of alveolar bone adjacent to the periodontal ligament in the pressure zone and apposition in the tension zone. There are also degenerative and formative changes seen in the periodontal ligament.³