Impact of presurgical orthodontic decompensation on alveolar bone morphology and defects in patients with skeletal Class III high-angle malocclusion.

Introduction: This retrospective study aimed to evaluate the morphology of the alveolar bone and to assess the incidence of fenestration and dehiscence during presurgical orthodontic decompensation in patients with skeletal Class III malocclusion.

Methods: The study included 60 patients with skeletal Class III high-angle malocclusion who had completed presurgical orthodontic treatment. Lateral cephalograms and cone-beam computed tomography images were obtained before (T0) and after (T1) the presurgical orthodontics. The labial inclination angles of the mandibular central incisors were measured using lateral cephalograms. Cone-beam computed tomography images evaluated alveolar bone thickness and height along the roots of the target teeth and assessed the incidence of fenestration and dehiscence. Statistical analyses were conducted using paired t tests, chi-square tests, and binary logistic regression.

Results: From T0 to T1, decompensatory movements of the mandibular central incisors resulted in a reduction in alveolar bone thickness and vertical height. Most teeth exhibited bone loss of 2 mm apical to the cementoenamel junction. The prevalence of labial bone defects increased significantly, rising from 51.7% to 73.3% in the mandibular left central incisor and from 51.7% to 76.7% in the mandibular right central incisor. Greater decompensation angles were linked to higher risks of fenestration and dehiscence at T1. When the probability of bone defect occurrence was set at 50%, the thresholds for changes in the IMPA and L1-NB were found to be 5.47° and 5.91°, respectively.

Conclusions: The threshold for decompensation of the mandibular central incisors is relatively low in patients with skeletal Class III high-angle because of the anatomically thin alveolar bone. Exceeding this threshold increases the risk of bone defects. Therefore, careful evaluation of the periodontal condition is essential when establishing treatment objectives to prevent adverse periodontal outcomes.