Effects of Orthognathic Surgery on Perioral Muscle Function: A Comparative Analysis Between Class II and Class III Female Patients

Purpose The purpose of this study was to investigate changes in lip-closing force, tongue pressure, and buccinator pressure before and after orthognathic surgery, and to compare these changes between skeletal Class II and Class III female patients. Materials and Methods Thirty-six female patients who underwent orthognathic surgery at Kyushu Dental University Hospital were enrolled. Patients were divided into two groups (Group A: skeletal Class II; Group B: skeletal Class III), and ten females with normal occlusion served as the control group. Lip-closing force, tongue pressure, and buccinator pressure were measured one day before surgery, and at three months and one year postoperatively. Maximum values were analyzed using the Mann–Whitney U test and Wilcoxon signed-rank sum test. Results Lip-closing force, tongue pressure, and buccinator pressure significantly increased one year after surgery in both groups (p < 0.05), although a temporary decline was observed at three months postoperatively, except for lip-closing force in Group A. The change rates for lip-closing force and buccinator pressure were higher in Group A, whereas tongue pressure increased more in Group B. However, a statistically significant difference was observed only in lip-closing force (p < 0.05). Conclusion Orthognathic surgery significantly improves perioral muscle function as well as facial aesthetics. Enhancements in lip-closing force and buccinator pressure were more pronounced in Class II patients compared to Class III patients.