Alveolar Bone Changes Following Incisor Retraction In Skeletal Classⅱ Patients

To evaluate alveolar bone change and correlation of maxillary central incisor movement in skeletal class II patients with different vertical growth patterns after incisor retraction. The study included 60 patients with skeletal Class II malocclusions who completed orthodontic treatment with incisor retraction. Cone-beam computed tomography (CBCT) was taken before(T1) and after (T2) orthodontic treatment. Each patient was further divided into high-angle and average-angle groups. For the maxillary central incisors, the alveolar bone height(ABH), alveolar bone thickness(ABT) at 3 levels and distance of coronal movement(SC) and apical movement(SR) were measured using CBCT images voxel-based superimposing based on stable skeletal region. Paired sample T test and independent samples t-test was used to compare T1 and T2 variables within and between groups, and Pearson’s correlation test and linear regression analysis were applied for evaluation. After treatment, ABT increased on labial side and decreased on palatal side in both groups. ABH on labial side in high-angle group showed no difference because of coronal intrusion. According to multivariate linear regression, change of ABT on palatal side could be predicted as follow: average-angle group: 0.1334+(-0.08632)×SR +(-0.4009)×change of torque(T1-T2), high-angle group: 0.2214+(-0.06958)×SR +(-0.6380)×change of torque(T1-T2). ABT and ABH showed significant differences between high-angle group and average-angle group before and after incisor retraction. Intrusion and apical movement of incisor were related to alveolar bone change.