Three-dimensional condylar displacement and remodelling following correction of asymmetric mandibular prognathism with maxillary canting

Long-term evaluation of condylar positional and volumetric parameters and skeletal stability in Class III bimaxillary orthognathic surgery patients

This retrospective study examined long-term (4-5 years) condylar positional and volumetric changes and skeletal stability after bimaxillary orthognathic surgery in skeletal Class III patients. Pre-surgical (T0: 0.9 ± 1.1 months) and post-surgical (T1: 0.6 ± 0.7 months; T2: 12.8 ± 3.1 months; T3: 56.5 ± 6.5 months) cone beam computed tomography (CBCT) images of 22 patients were obtained. CBCT multiplanar reformation (MPR) images were generated, and three-dimensional (3D) condylar models were constructed and superimposed to compare changes in condylar volume from pre- to postoperative. Condylar position in the sagittal and coronal planes altered immediately after surgery; however at long-term follow-up, the condyles had returned to their pre-surgical position. The condyles remained slightly inwardly rotated at short-term (-2.6°, 95% confidence interval -3.5° to -1.7°) and long-term (-1.9°, 95% confidence interval -2.8° to -1.0°) follow-up. Changes in condylar volume were insignificant after surgery. Condylar positional changes had no effect on skeletal stability. However, patients with an increased face height prior to surgery and more retrusive jaw position postoperatively were more prone to condylar resorption. Surgical changes remained stable 4-5 years after surgery. In conclusion, condylar position changed insignificantly following surgical correction in Class III patients provided that the correct surgical technique was employed.

Early and 1-year postsurgical stability and its factors in patients with complicated skeletal Class Ⅲ malocclusion treated by conventional and surgery-first approach: A prospective cohort study

INTRODUCTION

This study aimed to compare postsurgical stability between conventional (CSA) and surgery-first (SFA) approaches and investigate its prognostic factors in patients with a skeletal Class Ⅲ extraction.

METHODS

Twenty and 19 patients treated with LeFort I osteotomy and bilateral sagittal split ramus osteotomy (BSSRO) with premolar extraction were enrolled in SFA and CSA groups, respectively. Serial cone-beam computed tomography images obtained before surgery, immediately after surgery (T1), 3 months after surgery, and 12 months after surgery were used for 3-dimensional quantitative analysis. The condyle was segmented for analyzing volumetric changes. Repeated measures analysis of variance, independent t test, and chi-square test were used to compare time-course and intergroup differences. Pearson and Kendall correlation and multivariate linear regression analyses were used to explore prognostic factors affecting skeletal stability.

RESULTS

In both CSA and SFA, postsurgical relapse mainly occurred in the mandible sagittal and vertical dimensions and during the first 3 months after surgery. Stability in SFA was significantly less than that in CSA. Intraoperatively, inferolateral condylar displacement with proximal segment inwards, clockwise rotation, and return movements after surgery were observed regardless of the treatment approach. The condylar volume remained stable over time. Multivariate regression analysis showed that posterior vertical dimension (VD) at T1 (-1.63 mm), surgical amount of mandibular setback (-10.33 mm), surgical condylar downwards displacement (-1.28 mm), and anterior overjet at T1 (6.43 mm) were the most important predictors of early mandibular relapse (r2 = 0.593).

CONCLUSIONS

The risk of early relapse could be reduced by controlling the anterior, middle, and posterior constraints provided by the prediction model.