Three-Dimensional Evaluation of the Effect of Maxillary Incisor Retraction on the Palatal Bone and Root Resorption

Introduction: The objective of this study was to compare pre-treatment and post-treatment cone-beam computed tomography images of patients to quantitatively evaluate the effect of orthodontically retracting maxillary incisors on the height and labiolingual thickness of labial and palatal alveolar bone and incisor apical root resorption. Methods: Maxillary central incisor apical root resorption, labial and palatal alveolar bone height, and labiolingual thickness were assessed on pre-treatment and post-treatment cone-beam computed tomography scans of 59 subjects (mean age, 13.00 years) with premolar extractions and 63 subjects (mean age, 13.40 years) who were treated with non-extraction therapy. Results: The mean incisor apical root resorption in the extraction group was 1.47± 0.70 mm, compared to 0.70± 0.81 mm in the non-extraction group (P\u3c 0.001). The extraction group also experienced greater palatal bone height loss (0.84± 1.08 mm) than the non-extraction group (0.22± 0.39 mm) (P\u3c 0.001). Increased root resorption was correlated with Class II malocclusion, increased OJ and OB, greater number of extracted premolars, long treatment duration, proximity of incisor roots to palatal cortex, and apical extrusion. Increased palatal alveolar bone height loss was correlated with greater number of extracted premolars, long duration of treatment, proximity of incisor roots to palatal cortex, and thin alveolar bone. Conclusion: Clinicians should exert caution when excessive incisor movement is planned in patients with thin alveolar bone