Changes of maxillary central incisor and alveolar bone in Class II Division 2 nonextraction treatment with a fixed appliance or clear aligner: A pilot cone-beam computed tomography study

Introduction: This retrospective clinical study investigated the clinical changes of maxillary central incisor and alveolar bone in Class II Division 2 nonextraction treatment with fixed appliances or clear aligners on the basis of cone-beam computed tomography. Methods: Fifty-nine Chinese Han patients with similar demographic characteristics were collected from a conventional bracket group, a self-ligating bracket group, and a clear aligner group. All measurements about root resorption and alveolar bone thickness on the cone-beam computed tomography images were tested. Changes between pretreatment and posttreatment were evaluated by paired-sample t test. The variation among the 3 groups was compared by 1-way analysis of variance. Results: The resistance center of the maxillary central incisor showed upward or forward movement, and the axial inclination was increased in 3 groups (P < 0.0001). Root volume loss in the clear aligner group (23.68 +/- 4.82 mm(3)) was significantly less than that in the fixed appliances group (28.24 +/- 6.44 mm(3) in the conventional bracket group, 28.17 +/- 6.07 mm(3) in the self-ligating bracket group) (P < 0.05). All 3 groups showed a significant decrease in palatal alveolar bone and total bone thickness at all 3 levels at posttreatment. In contrast, labial bone thickness significantly increased except for crestal level l. Among the 3 groups, the clear aligner group had a prominent increase in labial bone thickness at the apical level (P 5 0.0235). Conclusions: Clear aligner treatment for Class II Division 2 malocclusions could effectively reduce the incidence of fenestration and root resorption. Our findings will be beneficial to comprehensively understand the effectiveness of different appliances for Class II Division 2 malocclusions treatment. (Am J Orthod Dentofacial Orthop 2023;163:509-19)