Abstract: Objective To research the clinical effects of Forsus appliance on the hard tissue structure of the patients with skeletal mandibular retrusion at the peak stage of development,and to analyze condylar position change in articular fossa in the course of treatment.Methods 18 patients with a skeletal Angle Class Ⅱ mandibular retrusion were treated with Forsus appliance for an average period of 6.8 months.The sagital skeletal and dental changes were analyzed with reference to the lateral cephalograms before and after treatment.Condylefossa relationship changes were evaluated by means of magnetic resonanceimaging during the treatment.Results Table 1 showed that skeletal and dental data changed greatly,especially the mandible.The growth of mandible was promoted by Forsus appliance while the growth of maxilla was inhibited by Forsus appliance.The position of Condyles almost remained unchanged before and after treatment.Conclusions Forsus appliance has an significant orthopedic effect on bones at the peak stage of development and the physiology relationship of condyle and glenoid fossa recovers after treatment.

Key words: Forsus appliance, mandibule retrusion, condyle