The activator is one of the functional appliances. Activator could be used to correct Angle class Ⅱ malocclusion before growth or at growth period, and eventually, conduce desirable effects. Nowadays, scholars and clinical dentists from all over the world pay a great deal of attention to different kinds of activator. This review concentrates on the effects of activators, which consist of correction timing, matters needing attention for clinical application and modified design. Moreover, it is indicated here that bone impacts and the effects on the activities of masticatory muscles and temporomandibular joints should be considered gravely, and also the long-term stability of the effects after activator treatments.
