
Myofunctional therapy has been widely used for correction of developing Class II malocclusion. Since its inception various concepts about its mechanism of action has been proposed and investigated. However, not a single theory has been widely recognized. This review is an attempt to evaluate and compare all the theories described in orthodontic literature regarding working mechanism of myofunctional therapy in general and twin block appliance in particular. Subject Area: orthodontics and dentofacial orthopedics Keywords: myofunctional appliance, twin block, mechanism of action.