Abstract:

Objective　To investigate the relationship among the crown, root and the whole tooth position and to provide technical and data support for the future in-depth study.　Methods　29 adult skeletal Class III malocclusion patients who met the inclusion criteria were selected. They all were shot Cone-beam CT（CBCT）and the DICOM data were collected. The tilt angle and torque angle of all teeth (except the third molar) in the upper and lower jaws in skeletal Class III were measured respectively by the software Invivo5.1. Results　(1) In skeletal Class III malocclusion, there was a good consistency among the tooth crown, root and the whole tooth tip angles in the upper and lower jaws（P>0.05）. (2) In skeletal Class III malocclusion, there was a good consistency among the upper teeth crown, root and the whole teeth torque angles（P>0.05）. However there were great differences between the crown and the root torque angles in lower teeth except for the first molar（P<0.05）. And torque angles between the root and whole tooth were consistent in lower jaw (P>0.05).　Conclusions　(1) In skeletal Class III malocclusion, there is low consistency between the tilt angle of the crown and the root or the whole tooth, which may be ascribed to the discrimination error of the tooth position; (2) There is a good consistency between the tilting grade of the root and that of the whole tooth.

Key words: Skeletal class III malocclusion, Maxillary, Mandibulary, Mesio-distal angulation, Bucco-lingual inclination, CBCT