Mandible-Only Orthognathic Surgery Achieves Higher Accuracy Than Bimaxillary Surgery for Skeletal Class III Malocclusion

A previous study analyzing the accuracy of bimaxillary orthognathic surgery for class III malocclusion revealed its accuracy is lower in the mandible than in the maxilla. This raised the question of whether the discrepancy is due to inherent mandibular inaccuracy or is influenced by maxillary discrepancy. Although numerous studies have examined the indications, stability, and duration of treatment for both single-jaw and bimaxillary surgeries, few have focused on comparing their accuracies. To address this issue, the present retrospective study compared the accuracies of mandible-only surgery and bimaxillary surgeries (maxilla-first and mandible-first). The study included 96 patients who underwent orthognathic surgery from 2017 to 2024. Surgical accuracy was quantified by measuring the linear discrepancies between preoperative plans and postoperative results at landmarks using cone beam computed tomography. The linear discrepancy that was closer to 0 was considered the more accurate result. The mean 3D discrepancy was 0.99±0.31 mm in the mandible-only group, 1.70±0.75 mm in the maxilla-first group, and 1.41±0.46 mm in the mandible-first group (P<0.001). Using mandible-only surgery as the reference, multiple linear regression showed a significant difference between maxilla-first and mandible-only surgeries (P=0.002), but not between mandible-first and mandible-only surgeries. In conclusion, this study suggests that while mandible-only surgery is the most accurate approach in the mandible, the accuracy of the mandible-first approach is comparable to or exceeds that of the maxilla-first approach.