Surgery-First and Orthodontic-First Approaches Produce Similar Patterns of Condylar Displacement and Remodeling in Patients With Skeletal Class III Malocclusion

Abstract

Condylar displacement and remodeling are critically involved in occlusal and skeletal stability after orthognathic surgery. The aim of the present study was to characterize condylar displacement and surface remodeling after bimaxillary orthognathic surgery in adult patients with skeletal Class III malocclusion treated by the surgery-first approach (SFA) or the orthodontic-first approach (OFA). This retrospective cohort study recruited adult patients with mandibular hyperplasia treated with SFA or OFA. Simultaneous Le Fort I osteotomy for maxillary advancement and bilateral sagittal split ramus osteotomy for mandibular setback were performed in all patients. Original cone-beam computed tomographic data before surgery (T0), immediately after surgery (T1), and 12months postoperatively (T2) were collected and reconstructed for 3-dimensional (3D) quantitative analyses. Three-dimensional condylar displacement and remodeling after SFA and OFA were characterized and statistically compared by Mann-Whitney U test and χ2 test. The significance level was set at a P value less than .05. Twenty-four (male-to-female ratio, 1:2; mean age, 21.2yr) and 20 (male-to-female ratio, 1:1; mean age, 23.1yr) patients were enrolled in the OFA and SFA groups, respectively. Condylar inferolateral displacement with inward and anterior rotations from T0 to T1 and return movements from T1 to T2 were observed regardless of treatment approach. Significantly greater amount of 3D bodily shift immediately after surgery (2.04±1.05mm in SFA group vs 1.22±0.66mm in OFA group; P<.05) and downward movement 1year after surgery were observed in the SFA versus OFA group. Bone resorption in the condylar surface was prevalent and predominant in its lateral areas, whereas bone formation was frequently observed in the anteromedial area in the SFA (45%) and OFA (42.9%) groups. Similar patterns of 3D condylar displacement and surface remodeling were observed in patients treated with SFA or OFA.