Abstract: Objective　To investigate tip and torque characteristics of all teeth in patients with high-angle skeletal class III malocclusion in order to provide guidance for clinical treatment.   Methods　Dicom data of cone-beam CT (CBCT) of 24 patients with high-angle skeletal class I (13 patients) and III malocclusion (11 patients) meeting the inclusion criteria were collected. Tip and torque of all teeth (except the third molar) were measured respectively by the software Invivo5.1.　Results　(1) Inclination angle of the same name teeth had a good consistency in high-angle skeletal class I class III, P＞0.05； the data of the same name teeth were processed together hereinafter. (2) Comparison of sagittal direction between class III and I. In class Ⅲ malocclusion: ① It was showing a trend of increase in the lingual root torque of the anterior upper teeth, but only the canines had significant differences, P＜0.05; ② Lingual  root torque of  anterior lower teeth had decreased with significant difference, P＜0.05.③ There was no significant difference in the trend of mesio-inclination of the upper posterior teeth and distal inclination of the lower posterior teeth, P＞0.05.  (3)Horizontal comparison of direction of skeletal class I and Ⅲ: ①The distal inclination of the anterior teeth in the upper jaw increased with significant difference and  only distal inclination of incisors of the lower jaw  increased in significant differnce, P<0.05. ② Lingual  root torque  significantly increased in the upper posterior teeth but  decreased in the lower posterior teeth without statistical differnce. (4) Comparison of high-angle skeletal I and III with normal sagittal and coronal inclination of Andrews: ① Sagittal direction: lingual root torque of  the upper and lower anterior teeth of high-angle skeletal I and III increased and the upper and lower posterior teeth had significant mesio-inclination. ② Coronal direction: the distal inclination of the upper and lower anterior teeth of skeletal I and III with high angle increased, while the lingual torque of the upper and lower posterior teeth increased.　Conclusions　(1)The vertical compensation of high-angle skeletal class Ⅲ is more significant than that of sagittal compensation. (2) High-angle skeletal class Ⅲ of upper and lower anterior teeth have much higher risk of bucco (labial)-lingual tilting movement, and more attention should be paid to the overall movement of teeth when moving. (3) The posterior teeth of maxilla have obvious buccal inclination in high-angle skeletal class III and the lateral extension range of the upper dentition decreases, which may reduce the stability after arch expansion.

Key words: High- angle, Skeletal class Ⅲmalocclusion, Tip, Torque