Three-dimensional surgical changes of mandibular proximal segments affect outcome of jaw motion analysis

Purpose: Displacement of the mandibular proximal segments is inevitable in surgical correction of the asymmetric mandible. The aim of the present study was to assess the outcomes of jaw motion analysis (JMA) in relation to the changes in the mandibular proximal segments after orthognathic surgery (OGS). Patients and Methods: The present retrospective cohort study investigated the surgical changes using the cone-beam computed tomography records and the mandibular function with JMA and a temporomandibular joint (TMJ) examination. The predictor variables were the 3-dimensional (3D) changes in the proximal segments on the deviated and nondeviated sides. The outcome variables were the JMA data obtained 6 months after OGS. The Pearson correlation test was performed to assess the relationship between the surgical changes and the outcome of JMA. Results: Twenty-one adult patients with skeletal Class III malocclusion and mandibular deviation greater than 4 mm were included in the present study. The change of the ramus axis to the coronal plane on the deviated side correlated negatively with the laterotrusive movement of the mandible toward the deviated side (r = -0.452, P >.05). The changes in the distance from the condyles to the midsagittal plane and the angulation of the ramus axis to midsagittal plane on the nondeviated side correlated negatively with the condyle range of retrusion on both sides. However, the increase in the angulation of the ramus axis to the midsagittal plane on the nondeviated side correlated positively with the angle of the horizontal condylar movement in laterotrusion on the deviated side (r = 0.458, P <.05). Conclusions: 3D model visualization enabled us to clearly detect the changes in the proximal segments after OGS. A relationship between the condylar range of motion and skeletal changes in the proximal segments in patients with Class III malocclusion was observed, mainly on the deviated side of the mandible.