Evaluation of a safe decompensation range for mandibular incisors during presurgical orthodontic treatment for severe skeletal Class III malocclusion: A cone-beam computed tomography study.

INTRODUCTION

The objective of this study was to systematically evaluate cortical bone remodeling and mandibular incisor movement during presurgical orthodontic decompensation in patients with severe skeletal Class III malocclusion and explore more suitable indicators for determining the decompensation range.

METHODS

Cone-beam computed tomography images of 46 patients with severe skeletal Class III malocclusion who underwent presurgical orthodontic treatment were analyzed. Vertical bone loss (sagittal view) was measured, and cortical bone remodeling and mandibular tooth movement (coronal view) were assessed at the crestal, midroot, and apical levels. Patients were grouped by their degree of alveolar bone deterioration. Mandibular incisor inclination angle (the angle between the long axis of the mandibular central incisor [MCI] and the long axis of the mandibular symphysis) and incisor mandibular plane angle (the angle between the long axis of the MCI and the mandibular plane) were compared between groups using t tests.

RESULTS

MCIs exhibited tipping movement, with prominently increased lingual alveolar bone defects after decompensation. The mean mandibular incisor inclination angles were as follows: (1) pretreatment was 4.45° for group 1 (with better alveolar bone conditions) and 2.99° for group 2 (with worse alveolar bone conditions) (P = 0.252), and (2) posttreatment (after decompensation) was 10.91° for group 1 and 19.31° for group 2 (P <0.001). The mean incisor mandibular plane angles were as follows: (1) pretreatment was 77.63° for group 1 and 71.64° for group 2 (P <0.05), and (2) posttreatment was 85.95° for group 1 and 84.84° for group 2 (P = 0.624).

CONCLUSIONS

Instead of decompensating until the mandibular incisors are nearly upright relative to the mandibular plane, the relationship with the mandibular symphysis should be prioritized for healthier considerations.