Abstract
BACKGROUND: This study aimed to compare three-dimensional (3D) alveolar bone changes and root resorption in skeletal Class I malocclusion treated with fixed appliances (FAs) or clear aligners (CAs), under extraction and non-extraction protocols, using Cone-beam computed tomography (CBCT). MATERIALS AND METHODS: This retrospective study involved 120 adult patients, divided into an equal groups of non-extraction and extraction treatment. Each group received either FAs or CAs. A total of 960 incisors from all patients, and 480 canines and second premolars from 60 patients in the extraction group, were analyzed. CBCT scans were evaluated using InVivo 6.0.3 software for 3D measurements of alveolar bone thickness (ABT), height (ABH), root length, and bone defects. All patients underwent CBCT scans immediately before- (T0) and after-treatment (T1). The reported measurements represent the changes between these two time points. Intra-group comparisons were analyzed using paired t-tests, and inter-group comparisons were examined using independent t-tests. Statistical significance was set at P < 0.05. RESULTS: In the non-extraction group, FAs demonstrated greater increases in labial ABT at upper central incisors (U1) and lateral incisors (U2), with smaller reductions at lower central incisors (L1) compared to CAs. FAs also resulted in more pronounced decreases in lingual ABT at U1 and L1 but showed larger increases at U2 and L2. In the extraction group, FAs induced more labial thickening at L1 and L2, greater lingual thinning at U1 and L1, and higher levels of root resorption, particularly at U2 and L1. FAs also triggered larger increases in bone measurements at upper canines and second premolars (P < 0.05). CONCLUSION: Fixed orthodontic appliances resulted in more pronounced alveolar bone remodeling and root resorption compared to clear aligners, most notably in extraction cases. While Clear aligners helped in preserving labial bone and minimizing root resorption, neither method completely averted bone loss. Therefore, treatment decisions should take into account clinical objectives, anatomical risks, and patient factors. TRIAL REGISTRATION: Not applicable.