Abstract:

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.

Key words: Malocclusion, Angle class Ⅱ, Cone-beam computed tomography, Crown-root angle, Surface-shaft angle