Abstract: PURPOSE: During orthodontic treatment, the incisors in patients with Class Ⅱ division 1 and division 2 malocclusion showed different clinical features, which determine the different ways to move the teeth to the suitable position. This study analyzed the morphology of alveolar bone around upper central incisor with cone-beam CT (CBCT). METHODS： The sample consisted of 20 normal malocclusion and 40 patients with Class Ⅱ malocclusion （division 1 20 cases and division 2 20 cases）. CBCT images before orthodontic treatment were reconstructed by INVIVO 5.0 image processing software. Paired t test was used for statistical analysis with SPSS 19.0 software package. RESULTS: At the upper central incisors, the alveolar thickness between normal malocclusion and Class Ⅱ division 1 and division 2 malocclusion had significant difference except the palate thickness between normal malocclusion and Class Ⅱ division 2 malocclusion (P<0.05). CONCLUSIONS: Orthodontist should consider the relationship between the teeth position and alveolar bone shape comprehensively, choose the correct plan in order to avoid root desorption, alveolar bone loss, fenestration and other adverse reactions.

Key words: Class Ⅱ division 1 malocclusion, Class Ⅱ division 2 malocclusion, Cone-beam CT, Alveolar bone thickness of upper anterior teeth