Objective : To explore the influence of apical dense bone islands on tooth movement during orthodontic treatment and its complications, and to provide a reference for orthodontic clinical treatment. Methods : This study obtained approval from the hospital ethics committee. A retrospective analysis was conducted on 33 patients with apical dense bone islands who received full-mouth fixed orthodontic treatment in the Orthodontics Department of Huizhou Stomatological Hospital from 2018 to 2022. Cone-beam CT (CBCT) was used to determine the location, distribution, and wrapping severity of the apical dense bone islands before treatment. The number of loose teeth located in the apical dense bone islands and the degree of external apical root resorption in the apical area of teeth were analyzed before treatment, immediately after treatment, and 12 months after treatment. Results: There were 33 orthodontic patients (aged 11 to 42 years, with an average age of 16.7 years and a median age of 15 years) included in this study, including 12 males (36.4%) and 21 females (63.6%). All apical dense bone islands involved a single tooth located in the mandible, mainly in the premolar-molar area. No gender differences were present in the location of the dense bone islands (P>0.05). The apical dense bone islands were mildly wrapped in 23 cases (69.7%), moderately wrapped in 10 cases (30.3%), and severely wrapped in no cases. No difficulty in tooth movement or incomplete closure of extraction space was found in the apical dense bone islands with different degrees of wrapping during orthodontic treatment. For teeth located in apical dense bone islands, 1 patient (3.0%) had loose teeth before treatment, 6 patients (18.2%) had loose teeth after treatment, and 2 patients (6.1%) had loose teeth 12 months after treatment. The number of patients with grade I loose teeth increased after treatment and 12 months after treatment. There was a statistically significant difference in the number of loose teeth before and after treatment (P<0.05), no statistically significant difference in the number of loose teeth before treatment and 12 months after treatment (P>0.05), and no statistically significant difference in the number of loose teeth after treatment and 12 months after treatment (P>0.05). After treatment, apical dense bone islands showed mild resorption in 26 cases (78.8%), moderate resorption in 7 cases (21.2%), and severe resorption in no cases. The apical dense bone islands showed mild resorption in 25 cases (75.8%), moderate resorption in 8 cases (24.2%), and severe resorption in no cases 12 months after treatment. For the severity of root resorption, there was a statistically significant difference between before and after treatment (P<0.05) as well as between before treatment and 12 months after treatment (P<0.05). However, no statistically significant difference was observed between after treatment and 12 months after treatment (P>0.05). Conclusion Apical dense bone islands were not found to affect tooth movement during orthodontic treatment. After orthodontic treatment, the number of loose teeth increased and mild-to-moderate tooth external apical root resorption occurred, which may be a potential risk of external apical root resorption. Thus, it is recommended to pay close attention during the orthodontic process.