Clinical Study on Soft Tissue Changes Caused by Twin-Block Appliance in Patients with Mandibular Retrognathia

Objective To investigate the soft tissue changes caused by Twin-Block appliance which were used to treated Angle's class Ⅱ division 1 malocclusion with mandibular retrognathia.Methods 20 patients in growth stage with Angle's Class Ⅱ division 1 malocclusion and mandibular retrognathia were investigated.Cephalometric analysis was carried out before and after the treatment of Twin-Block appliance.Data were analyzed by SPSS11.0 system using paired t-test.Results There were significant increases in FH-H'Pg' angle(P0.01)and Sn-H(P0.05),while 1-LZ and H-H'Pg' angle and Li-H and Si-H decreased(P0.05).Conclusion Twin-Block appliance can reset the mandible forward on Angle's Class Ⅱ division 1 malocclusion patients with mandibular retrognathia,while the thickness of patient's lips decreased and it contributed to a better profile.