目的：借助锥形束CT（cone-beam computed tomography，CBCT）结合计算机辅助测量技术，描述研究安氏Ⅱ类2分类错牙合畸形上前牙的冠根形态，为此类错牙合畸形的临床治疗提供指导。方法：从就诊于北京大学口腔医院正畸科的患者中分别选取诊断为安氏Ⅱ类2分类错牙合、安氏Ⅰ类错牙合者各18例（以下简称为Ⅱ类2组、Ⅰ类组），所有患者于治疗前均拍摄了CBCT 影像，在InvivoDental 5.0图像处理软件中利用多平面重建方法截取上前牙唇舌向最大截面图，在此截图上从冠根角、面轴角两方面分析研究两组间上前牙的冠根形态差异。所得数据输入SPSS 20.0统计软件进行统计分析，采用t检验比较Ⅰ类组及Ⅱ类2组冠根角、面轴角差异，以及Ⅱ类2组冠根角与冠根角为180°时的差异，检验水准为双侧α=0.05。结果：Ⅰ类组上颌中切牙、侧切牙、尖牙冠根角分别为179.08°±3.31°、176.55°±2.77°和184.20°±2.51°，面轴角分别为21.00°±2.63°、19.63°±2.35°和19.36°±2.30°；Ⅱ类2组上颌中切牙、侧切牙、尖牙冠根角分别为176.80°±2.62°、174.13°±3.28°和181.79°±2.88°，面轴角分别为23.20°±2.95°、22.29°±2.19°和20.61°±2.34°，除尖牙面轴角外，与Ⅰ类组相比差异均有统计学意义。Ⅱ类2组各上前牙冠根角与冠根角为180°时比较差异均有统计学意义，即这些牙的牙冠长轴和牙根长轴不都在同一直线上，存在冠根成角的现象。结论：安氏Ⅱ类2分类错牙合畸形患者上前牙具有更特殊的冠根形态，即牙冠长轴与牙根长轴明显成角，上切牙牙冠相对牙根明显舌倾，牙冠唇面形态有别于安氏Ⅰ类错牙合畸形的患者，这对治疗后牙根位置和转矩表达都会有影响，提示治疗此类患者需要考虑其上前牙的冠根形态，上前牙移动的理想位置应由牙根而不是牙冠的位置决定。

Objective： To study crown-root morphology of maxillary anterior teeth in Class Ⅱ, division 2 malocclusion using cone-beam CT (CBCT) combined with computer aided measurement technology to provide guidance for clinical treatment. Methods: The samples which consisted of 36 cases radiographed with CBCT techniques were selected and divided into two groups (18 each ) based on the type of malocclusion presented: Class Ⅱ, division 2 group (groupⅡ2) and Class Ⅰ group (groupⅠ). The measurements of crown-root morphology including crown-root angle and surface-shaft angle were got by Multiple Planer Reconstruction of CBCT data uploaded into InvivoDental software 5.0. The data were processed with SPSS 20.0 software package and t test was employed for comparison of angular measurements. Results: In group Ⅰ, crown-root angles of maxillary central incisor, maxillary lateral incisor and maxillary canines were 179.08°±3.31°, 176.55°±2.77°and 184.20°±2.51° respectively, surface-shaft angles were 21.00°±2.63°, 19.63°±2.35° and 19.36°±2.30° respectively. While in group Ⅱ 2, crown-root angles of maxillary central incisor, maxillary lateral incisor and maxillary canines were 176.80°±2.62°, 174.13°±3.28° and 181.79°±2.88° respectively, surface-shaft angles were 23.20°±2.95°, 22.29°±2.19° and 20.61°±2.34° respectively. Compared with group Ⅰ, significant statistical differences were observed with the exception of surface-shaft angle of maxillary incisor. There was significant difference in crown-root angle between group Ⅱ 2 and 180°.Conclusion: The maxillary anterior teeth in Class Ⅱ, division 2 malocclusion exhibited significant crown-root morphology which would influence the torque after orthodontic treatment. Special attention should be paid to the position of maxillary anterior teeth roots during orthodontic treatment for Class Ⅱ, division 2 malocclusion. The ideal position of tooth movement should be decided by the root rather than the location of the crowns.