目的：探索建立一种非锥形束计算机断层扫描（cone beam computerized tomography, CBCT）依赖的成人矫治前后下颌三维数字化模型重叠的方法，为三维评价下颌牙齿移动提供手段，同时验证此方法的准确性。方法：纳入于北京大学口腔医院正畸科拔除第一前磨牙矫治的成人患者15例，获取患者治疗前后牙颌石膏模型及颅面CBCT。石膏模型经激光扫描转化为数字化模型，CBCT通过正交投照生成头颅侧位片。建立基于头颅侧位片的下颌模型重叠法：通过上颌模型腭部稳定区域重叠、咬合关系转移以及头颅侧位片重叠获得的下颌骨旋转和平移量的校准，最终实现下颌模型的重叠。以基于CBCT的下颌模型重叠法为参照，建立共同的三维坐标系，测量下颌中切牙、尖牙和第一磨牙的三维移动量，通过配对t检验评价基于头颅侧位片的下颌模型重叠方法的准确性。结果：两组重叠法结果相比，下颌第一磨牙在三维移动量上差异无统计学意义。下中切牙和尖牙在矢状向和垂直向上的移动差异无统计学意义，横向上差异为(0.3±0.5) mm（P<0.05）。结论：通过结合上颌数字化牙颌模型重叠和头颅侧位片重叠计算的下颌变化，可以实现成人矫治前后下颌数字化牙颌模型的较准确的配准，前牙区横向测量存在少量误差，该方法适用于在没有CBCT的条件下利用正畸常规资料实现下颌模型的重叠。

Objective： To explore a cone beam computed tomography (CBCT)-independent method for mandibular digital dental cast superimposition to evaluate threedimensional (3D) mandibular tooth movement after orthodontic treatment in adults, and to evaluate the accuracy of this method. Methods: Fifteen postextraction orthodontic treatment adults from the Department of Orthodontics, Peking University School and Hospital of Stomatology were included. All the patients had four first premolars extracted, and were treated with straight wire appliance. The pre- and post-treatment plaster dental casts and craniofacial CBCT scans were obtained. The plaster dental casts were transferred to digital dental casts by 3D laser scanning, and lateral cephalograms were created from the craniofacial CBCT scans by orthogonal projection. The lateral cephalogram-based mandibular digital dental cast superimposition was achieved by sequential maxillary dental cast superimposition registered on the palatal stable region, occlusal transfer, and adjustment of mandibular rotation and translation obtained from lateral cephalogram superimposition. The accuracy of the lateral cephalogram-based mandibular digital dental cast superimposition method was evaluated with the CBCT-based mandibular digital dental cast superimposition method as the standard reference. After mandibular digital dental cast superimposition using both methods, 3D coordinate system was established, and 3D displacements of the lower bilateral first molars, canines and central incisors were measured. Differences between the two superimposition methods in tooth displacement measurements were assessed using the paired t-test with the level of statistical significance set at P<0.05. Results: No significant differences were found between the lateral cephalogrambased and CBCT-based mandibular digital dental cast superimposition methods in 3D displacements of the lower first molars, and sagittal and vertical displacements of the canines and central incisors; transverse displacements of the canines and central incisors differed by (0.3±0.5) mm with statistical significance. Conclusion: The lateral cephalogram-based mandibular digital dental cast superimposition method has the similar accuracy as the CBCT-based mandibular digital dental cast superimposition method in 3D evaluation of mandibular orthodontic tooth displacement, except for minor differences for the transverse displacements of anterior teeth. This method is applicable to adult patients with conventional orthodontic treatment records, especially the previous precious orthodontic data in the absence of CBCT scans.