Study on the Effect of the Twin-block Appliance and the Fixed Orthodontics Appliance on class II Division 1 Malocclusion and Retrognathic Mandible

Objective:Method:The study consisted of 9 children with class II division 1 malocclusion and retrognathic mandible.(average 11.5years old) was treated with Twin-block appliance for 4~6 months,and then undergone the Fixed treatment.The cephalometric data before and after treatment or control was analyzed statistically.Result:After treated The SNB angle increased;the SNB angle decreased,N-Me and ANS-Me increased,the overjet increased,all of which were statistically significant(P0.05).Conclusion:The functional treatment with Twin-block appliance to make the chin moved forward,which increased the SNB degree and decreased the ANB degree.Deep overbite,deep overjet,molar relation and Class II profile were improved greatly,which indicate that Twin-block appliance promote the mandibular growth sagittally and vertically,the correction of Class II skeletal relation and soft tissue profile can be achieved.