Three-dimensional evaluation of postsurgical stability of Surgery-first approach in Skeletal Class III patients with two-jaw surgery and maxillary premolar extraction and study of the influencing factors.

Abstract

Objectives to evaluate three-dimensional postsurgical stability of surgery-first approach with 2-jaw surgery and maxillary premolar extraction in skeletal class III patients and excavate factors influencing the relapse. Material and methods 24 patients were enrolled in this prospective cohort study. Serial cone-beam computer tomography images were superimposed and measured the surgical stability at the presurgical examination, 1 week, 3 month, 6 month and 12 month postoperatively. Patients were grouped by the amount of mandible sagittal relapse(stable group, n = 8; highly unstable group, n = 7). Skeletal and dental morphological variables, the amount of surgical changes, and orthodontic-related variables were compared between groups and analyzed for correlations with postsurgical stability. Results Considerable amount of pronation relapse on mandible were within three month postoperatively. The maxilla remained clinically stable. The coronoid process height, posterior maxillary height, the mandibular setback, distal segment intraoperative rotation and the amount maxillary second molar orthodontic intrusion showed significant difference between groups. The above variables, mandibular height, occlusal vertical dimension, and the mandibular and anterior maxillary intraoperative descent were significantly correlated with postoperative instability. Conclusions Mandibular pronation relapse mainly in the first three months after surgery.The maxilla postsurgical position is clinically stable. The factors for instability in the surgery-first approach include a longer coronoid process, longer facial height, a wider occlusal vertical dimension, greater surgical setback and descent, and more maxillary second molar intrusion. Clinical relevance Results can provide reference for patient selection, surgical planning and preoperative dental alignment stimulation for surgery-first approach. Trial Registration ChiCTR2200055787