Mandible-First Sequencing Increase Surgical Accuracy for Patients With Skeletal Class II Malocclusion Concomitant With Unstable Condyle-Fossa Relation.

The aim of this study was to explore whether mandible-first sequencing increases the surgical accuracy in bimaxillary orthognathic surgery for patients with skeletal class II malocclusion concomitant with the unstable condyle-fossa relation. A retrospective evaluation of 19 patients who had undergone virtually planned double-splint orthognathic surgery with different operation sequences was performed: maxilla-first (n=9) or mandible-first (n=10) surgery. The centroid position, translational, and rotational differences in the maxilla were evaluated by comparing the virtual plans with actual results. The stability was assessed by comparing the actual results with the follow-up outcomes 6 months postoperatively. The accuracy of the maxilla centroid position was improved in mandible-first sequencing surgery: mandible-first 1.87+/-0.94 mm versus maxilla-first 2.70+/-0.75 mm ( P <0.05). Moreover, no significant difference was detected in the translational and orientational discrepancies between the 2 groups. Neither sequencing procedure differed in the overall stability: maxilla-first (1.48+/-1.13 mm) versus mandible-first (1.57+/-0.90 mm). This study indicated that the mandible-first surgery leads to a more accurate maxilla position than the maxilla-first surgery for patients with skeletal class II malocclusion concomitant with the unstable condyle-fossa relation.