[A cone-beam computed tomography study on crown-root morphology of maxillary anterior teeth in Class II, division 2 malocclusion].

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 (group II 2) and Class I group (group I). 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 degrees +/- 3.31 degrees , 176.55 degrees +/- 2.77 degrees and 184.20 degrees +/- 2.51 degrees respectively, surface-shaft angles were 21.00 degrees +/- 2.63 degrees , 19.63 degrees +/-2 .35 degrees and 19.36 degrees +/- 2.30 degrees respectively. While in group II 2, crown-root angles of maxillary central incisor, maxillary lateral incisor and maxillary canines were 176.80 degrees +/- 2.62 degrees , 174.13 degrees +/- 3.28 degrees and 181.79 degrees +/- 2.88 degrees respectively, surface-shaft angles were 23.20 degrees +/- 2.95 degrees , 22.29 degrees +/- 2.19 degrees and 20.61 degrees +/- 2.34 degrees 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 degrees . 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.