Objectives: We aimed to quantify the displacement of the proximal segment after bilateral sagittal split osteotomy in patients with class III asymmetry and evaluate if the displacement was related to the movement of the distal segment.
Material and methods: Forty adults with class III asymmetry corrected by bimaxillary surgery were studied. Cone-beam computed tomography taken before and 1 week after surgery was used to measure the displacement of proximal segments and movement of the distal segment in terms of translation and rotation. The relationship between the displacemnt of the proximal segment and the movement of the distal segment was evaluated.
Results: After surgery, the deviated proximal segment was displaced forward and to the deviated side, rotated downward, tilted, and turned to the opposite side. The opposite proximal segment was displaced forward and rotated downward. The roll rotation of the proximal segment was correlated with the left/right movement and roll rotation of the distal segment.
Conclusion: Early after orthognathic correction for class III asymmetry, the deviated proximal segment was displaced in a direction favorable for correction of asymmetry. The roll rotation of the proximal segment was affected by the transverse movement and roll rotation of the distal segment.
Clinical relevance: Knowledge of the ability and limitation of the proximal segment rotation improves the virtual simulation.
Keywords: Class III malocclusion; Facial asymmetry; Orthognathic surgery; Proximal segment; Sagittal split osteotomy.