Comparison of Postoperative Stability Between BSSRO and Le Fort 1 Osteotomy with BSSRO in Skeletal Class III Malocclusion with Severe Open Bite.

Introduction: We aimed to investigate postoperative stability after orthognathic surgery in patients with skeletal class III malocclusion with severe open bite by comparison between bilateral sagittal splitting osteotomy (BSSRO) and BSSRO with Le Fort 1 osteotomy.

Materials And Methods: Seventeen patients with skeletal class III malocclusion with severe open bite who were needed more than 6 degree counterclockwise rotation of distal segment by only BSSRO in preoperative cephalometric prediction. The subjects were divided into group A, where 9 patients were treated by BSSRO, and group B, where 8 patients were treated by BSSRO with Le Fort 1 osteotomy. Patient's characteristics of age, gender, preoperative over jet (OJ) and over bite (OB) were not found to be significantly different between the two groups. Counterclockwise rotation of distal segment in preoperative cephalometric prediction by only BSSRO was not found to be significantly different between group A of 7.6 (6-10.6) degree and group B of 9 (6-13) degree. The amount of rotation was reduced to 5.4 (3-10) degree by bimaxillary surgery using BSSRO and Le Fort 1 osteotomy in group B. OJ and OB were measured as occlusal stability factor. Distance between ANS-to-PNS plane and the edge of upper incisor (NF-U1Ed), and distance between Menton and edge of lower incisor (Me-L1Ed) were measured as skeletal stability factor using cephalometric analysis. These lengths were measured at pre-surgery (T0), 2 weeks after surgery (T1) and 1 year after surgery (T2), and these differences between the two groups were statistically analyzed.

Results: OJ and OB kept a good relation at any experimental periods. The change of Me-L1Ed was significantly larger in group A (1.21 mm at T0-T1, 1.02 mm at T0-T2) than in group B (0.14 mm at T0-T1, 0.16 mm at T0-T2). The change of NF-U1Ed was not significantly different between group A (1.07 mm at T0-T1, 0.57 mm at T0-T2) and group B (0.51 mm at T0-T1, - 0.05 mm at T0-T2).

Conclusion: In case with more than 6 degree counterclockwise rotation of distal segment, skeletal stability was better after bimaxillary surgery than only BSSRO; however, OJ and OB kept a good relation.