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目的:本研究利用CBCT对正锁n 患者后牙颊舌向倾斜度及牙周硬组织进行三维数字化测量，比较正锁n 后牙与对照组后牙在牙齿水平上的差异，探索正锁n 后牙在牙槽骨中的空间位置和牙周硬组织特点。n 方法:选取后牙正锁n 的恒牙列患者30名，男性6名，女性24名，平均年龄为(25.0±7.6)岁。对照组为双侧后牙覆n 覆盖正常的恒牙列患者30名，男性4名，女性26名，平均年龄为(24.0±6.4)岁。正锁n 组最终纳入测量的为12对颌前磨牙(共24颗)、12对颌第一磨牙(共24颗)以及39对颌第二磨牙(共78颗)。对照组共有120对颌前磨牙(共240颗)、60对颌第一磨牙(共120颗)以及60对颌第二磨牙(共120颗)。拍摄CBCT，Dolphin Imaging软件测量牙槽骨中牙根位置、后牙颊舌向倾斜度和牙槽骨厚度，并对测量数据进行统计分析，其中对照组按照随机抽样原则随机抽取样本，保证锁n 组和对照组样本数量匹配。n 结果:卡方检验显示正锁n 组和对照组后牙牙根在牙槽骨中的位置无统计学差异。正锁n 组前磨牙和第二磨牙的转矩交角小于对照组，有显著性差异(n P<0.05)。正锁n 组前磨牙、第一磨牙和第二磨牙的牙长轴交角与对照组，均有统计学差异(n P<0.05)。正锁n 组上前磨牙颊侧牙槽骨厚度小于对照组，而下前磨牙大于对照组。正锁n 组第一磨牙，上下颌颊侧牙槽骨厚度在距釉牙骨质界(ECJ)根向6 mm和8 mm水平，均与对照组测量的结果有显著性差异(n P<0.05)。正锁n 组第二磨牙，上颌颊侧牙槽骨厚度在距ECJ根向4 mm水平及下颌颊侧牙槽骨厚度在距ECJ根向6 mm水平，与对照组的测量结果有显著性差异(n P<0.05)。除上颌前磨牙外，下颌前磨牙、上下颌第一磨牙及上下颌第二磨牙均显示出正锁n 组及对照组之间，根尖部位牙槽骨厚度存在统计学差异(n P<0.05)。n 结论:正锁n 后牙颊舌向的改变是倾斜移动和整体移动共同作用的结果。正锁n 第二磨牙的牙周风险可能较前磨牙和第一磨牙更高；正锁n 的下颌后牙比上颌后牙牙周风险更高。n “,”Objective:By using CBCT to measure buccolingual tooth inclination and alveolar bone thickness, and by comparing scissors-bite posterior teeth with normal posterior teeth, this study was in the purpose of exploring the tooth location within alveolar bone and the characteristics in periodontal hard tissue in subjects with posterior scissors-bite.Methods:CBCT images of 30 patients (6 males; 24 females; 25±7.6 years old) with posterior scissors bite and 30 patients (4 males; 26 females; 24±6.4 years old) with normal occlusion in posterior teeth were collected.12 pairs of opposing premolars (24 teeth), 12 pairs of opposing first molars (24 teeth) and 39 pairs of opposing second molars(78 teeth) were included in scissors-bite group. 120 pairs of opposing premolars (240 teeth), 60 pairs of opposing first molars (120 teeth) and 60 pairs of opposing second molars (120 teeth) were included in control group. CBCT images were analyzed by Dolphin Imaging software to measure the position of the root within alveolar bone, the buccolingual tooth inclination, the thickness of alveolar bone, and the thickness of the apical bone. The control sample were randomly selected from the control groups to match the sample number in the test group.Results:According to the position of the root in alveolar bone, the chi-square test showed that there were no statistically significant between scissors-bite group and control group. The torque angle of premolar and second molar in scissors-bite group were smaller than that in control group, statistically significant (n P<0.05). The long-axis angle in premolar, first molar and second molar scissors-bite group were statistically significant compared with control group (n P<0.05). The thickness of buccal alveolar bone in premolar in scissors-bite group was smaller than that in control group in maxilla and was larger than that in control group in mandible. In first molar group, the thickness of buccal alveolar bone at the level of 6 mm and 8 mm apically to the CEJ were significantly different from that of control group (n P<0.05). In second molar group, the thickness of buccal alveolar bone at the level of 4 mm in maxilla and 6 mm in mandible were significantly different from that of the control group (n P<0.05). Except for maxillary premolars, mandibular premolar, first molars and second molars showed statistically significance in apical bone thickness between scissors-bite group and control group (n P<0.05).n Conclusions:Posterior scissors-bite may be the result of a combination of buccal tipping movements and bodily movements. Periodontal risk of second molar with scissors-bite may be higher than that of premolars and first molar; the posterior periodontal risk is higher in mandible than in maxilla.