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目的:应用锥束计算机体层摄影技术(cone beam computed tomography, CBCT)与三维重建技术研究骨性Ⅲ类错n 患者上前牙的牙根吸收。n 方法:选取正畸正颌联合治疗的25例成年骨性Ⅲ类错n 患者，治疗前(T0)、术前正畸结束(T1)、治疗结束(T2)3个时期拍摄的大视野CBCT，应用数字化三维重建技术，测量上中切牙、上尖牙的牙根长度、牙根体积及根颈部、根体部牙根体积，探究正畸正颌联合治疗过程中牙根吸收的特点及不同牙位牙根形态变化的比较。n 结果:(1)上中切牙在术前正畸(T1-T0)及术后正畸(T2-T1)阶段牙根长度及牙根体积均有显著减小(n P＝0.000)，上尖牙牙根长度在术前正畸(T1-T0)阶段显著减小，牙根体积在术后正畸阶段(T2-T1)显著减小(n P＝0.000)；(2)上中切牙、上尖牙根颈部牙根体积吸收量(T2-T0)及其所占体积百分比均显著小于根体部，吸收量比例约为1∶2；(3)治疗过程中(T2-T0)，上中切牙与上尖牙体积吸收量无显著差异[上中切牙牙根体积吸收量(21.26±13.33) mmn 3，上尖牙(20.02±10.75) mmn 3]，上中切牙体积吸收量百分比(13.10±7.65)显著大于上尖牙(8.91±4.88)(n P＝0.031)。n 结论:骨性Ⅲ类错n 患者在正畸正颌联合治疗过程中，上中切牙及尖牙牙根长度和体积均发生了有统计学意义的牙根吸收，不能忽视根颈部的体积减小。上中切牙较尖牙牙根损伤程度更明显。牙根体积测量为探索牙根吸收提供了更多角度、更敏感的途径。n “,”Objective:To investigate root resorption of maxillary anterior teeth in skeletal class Ⅲ patients using cone beam computed tomography (CBCT) three-dimensional reconstructed images.Methods:The samples consisted of 25 skeletal class Ⅲ patients who went through orthodontic-surgical treatment. CBCT data of each patient at T0 (pretreatment), T1(preoperative), T2(posttreatment) were acquired and 3D digital root models were reconstructed. Root length and segmented root volumes(whole root, cervical part and apical part) of maxillary central incisors and canines were calculated to investigate the characteristics of root resorption between different teeth positions during the orthodontic-surgical treatment.Results:(1) Maxillary central incisors exhibited significant decrease of root length and volume in presurgical stage (T0 to T1) and postsurgical stage (T1 to T2 )(n P=0.000), Maxillary canines showed significant root length decrease during presurgical stage (T0 to T1) while apparent volume resorption happened during postsurgical stage (T1 to T2)(n P=0.000). (2) Maxillary central incisors and canines showed less volume resorption in cervical root than apical root. The ratio of the mean amount of volume change were about 1: 2; (3) From stage T0 to T2, the changing amount of root volume showed no difference between maxillary central incisors and canines (maxillary central incisor (21.26±13.33) mmn 3, maxillary canine (20.02±10.75) mmn 3), but maxillary central incisors had greater proportion of changing amount (13.10±7.65%) than maxillary canines (8.91±4.88%) (n P=0.031).n Conclusions:During the course of orthodontic-surgical treatment of skeletal class Ⅲ patients, maxillary central incisors and canines showed apparent root length decrease and volume resorption, and cervical root resorption could not be ignored. Maxillary central incisors resorb worse than canines. The volume measurement provides a new sensitive way to explore root resorption.