Abstract: BACKGROUND: Based on cone-beam CT measurement, the research group has found that the dental inclination characteristics of class III malocclusion are compensated due to the influence of the vertical direction. As a population group with a high incidence of class II malocclusion, there are different diagnoses and treatment strategies in Chinese people with different skeletal types, which is speculated to be related to the compensation difference of dental inclination.
OBJECTIVE: To explore the sagittal and coronal inclination characteristics of the whole tooth axis in different vertical skeletal types of class II malocclusion in order to provide guidance for clinical diagnosis and treatment. 
METHODS: Dicom data of cone-beam CT images were collected from 70 patients with skeletal class II malocclusion (middle angle: 30 cases, high angle: 20 cases, low angle: 20 cases) and 30 patients with middle-angle skeletal class I. The tipping angle and torque of all teeth were measured and compared by the software Invivo 5.1. 
RESULTS AND CONCLUSION: (1) In skeletal class II malocclusion, there was a statistically significant difference in the dental inclination of low-angle skeletal class II and high-/middle-angle skeletal class II, while the dental inclination of high- and middle-angle skeletal class II was basically similar. (2) Comparison of low-angle with middle- and high-angle skeletal class II: In the sagittal plane, the positive torque of the anterior upper teeth decreased and the anterior lower teeth were relatively upright, while mesio-inclination of the upper posterior teeth decreased and mesio-inclination of the lower posterior teeth increased. In the coronal plane, there was a significant difference in the trend of mesio-inclination of the upper and lower canines with low-angle class II (P < 0.05). (3) Comparison of skeletal class II and middle-angle skeletal class I: In the sagittal plane, except for anterior lower teeth, the characteristics of tooth inclination of middle-/high-angle class II and middle-angle class I are basically similar; however, there was significant difference between the two groups and low-angle class II (P < 0.05). For the anterior lower teeth, the skeletal class II malocclusion group showed no significant difference; however, compared with middle-angle class I, the labial inclination of the anterior lower teeth had increased. In the coronal plane, for the posterior teeth, the inclination characteristics of skeletal class II were similar. However, compared with skeletal class I, the posterior upper teeth showed a lingual inclination trend and the posterior lower teeth showed a buccal inclination trend. Moreover, there were statistically significant differences among upper second premolars, first molars, second molars, and lower first molars (P < 0.05). For the anterior teeth, there was no significant difference between class II and class I malocclusions. To conclude, skeletal class II malocclusion has the dental compensation of the anterior lower and posterior teeth, and the dental compensation of low-angle class II is more significant than that of high- and middle-angle class II. The sagittal inclination of low-angle skeletal class II malocclusion is related to the rotation of the jaw.

Key words: skeletal class II malocclusion, vertical skeletal type, torque, tipping angle, cranial cone-beam CT