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目的 探讨正畸-正颌联合治疗骨性Ⅲ类错(牙合)畸形的上颌第一磨牙代偿特征,为临床医师制定矫治计划提供参考.方法 选取2011年2月至2015年1月于北京大学口腔医学院·口腔医院正畸科完成正畸-正颌联合治疗的骨性Ⅲ类错(牙合)畸形成年患者48例(男性22例,女性26例),根据上颌减数与否分为减数组(28例)和非减数组(20例).采用激光扫描仪扫描矫治前后的牙颌模型.使用Rapidform 2006软件测量上颌第一磨牙的轴倾和转矩,获得并对比两组上颌第一磨牙的代偿特征数据.结果骨性Ⅲ类错(牙合)畸形矫治后减数组与非减数组上颌第一磨牙的轴倾、转矩差异均无统计学意义(P=0.150,P=0.144);矫治前减数组转矩的中位数(下四分位数,上四分位数)为-3.32°(-5.10°,1.16°),非减数组转矩为-6.94°(-13.06°,-0.42°),两组差异有统计学意义(P=0.005),即减数组颊倾代偿更明显.结论骨性Ⅲ类错(牙合)畸形患者上颌第一磨牙颊向倾斜代偿,其颊倾代偿越明显,术前正畸去除上颌后牙代偿越需要间隙,正畸方案越有可能考虑减数.“,”Objectives To investigate the compensation of upper first molar in adult skeletal class Ⅲ patients.Methods The sample consisted of 48 skeletal class Ⅲ patients with orthodontic-surgical treatment from February 2011 to January 2015 in Peking University School and Hospital of Stomatology.They were allocated into 2 groups based on extraction,28 patients in extraction group and 22 patients in non-extraction group.Dental casts were taken before and after treatment,and all the casts were scanned with a computer-assisted three-dimensional (3D) scanning system.Acquired 3D data were analyzed by Rapidform 2006.The tip and torque of the upper first molar were measured and analyzed.Results The tip and torque of the upper first molar in the skeletal class Ⅲ patients after treatment had no difference between extraction group and non-extraction group (P=0.150,P=0.144).The torque of upper first molar in extraction group [-3.32° (-5.10°,1.16°)] before treatment was bigger than that in non-extraction group [-6.94° (-13.06°,-0.42°)](P=0.O05),and the inclination of upper first molar in extraction group was more obvious.Conclusions In skeletal class Ⅲ patients,the upper first molar inclined buccally to compensate the discrepancy and extraction was usually necessary for decompensation.