Poster 48: Effect of Sex on Masseter Muscle Thickness 3 Years After Orthognathic Surgery

Abstract

The masseter muscle has been investigated by different imaging exams such as ultrasound. Individuals with Class III dentofacial deformities have a smaller masseter muscle thickness. To analyze whether sex influences masseter muscle thickness in patients with Class III dentofacial deformity and to determine the changes that occur with integrated orthodontic treatment, orthognatic surgery and orofacial myofunctional therapy 3 years after orthognathic surgery. The study was approved by the Research Ethics Committee and all participants gave written informed consent to participate. Materials and methods: A longitudinal study was conducted on 13 patients with Class III dentofacial deformities, denoted here as group P1 (before surgery); 3 patients were males aged 21 to 25 years (mean age: 22 years) and 10 were females aged 22 to 42 years (mean age: 27 years) and group P3 (same patients 3 years to 3 years and 8 months after surgery). All patients were submitted to orthodontic treatment before and after surgery and to speech therapy follow-up, as part of the routine of the service. Fifteen individuals with no changes in facial morphology or dental occlusion were assigned to the control group (CG), 11 females aged 21 to 29 years (mean age: 24 years) and 4 were males aged 19 to 25 years (mean age: 21 years). Masseter muscle ultrasonography was performed in the resting and biting situations in the three groups. The method error was calculated and the mixed-effects linear regression method was used to determine differences in masseter muscle thickness between sexes in the 3 groups. The model was adjusted using the SAS software, version 9.0, and the level of significance considered was P < .05. In CG men had significantly greater masseter thickness than women both in the resting and biting situations (P < .05). No significant gender difference was observed in P1 (P > .05), whereas left masseter muscle thickness at rest was greater in P3 men (P < .05) and tended to differ significantly for the right masseter also in the resting situation (P = .07). Masseter muscle thickness was influenced by sex, but not in patients with Class III dentofacial deformity; however, 3 years after orthognathic surgery in an integrated treatment, the difference in muscle thickness between men and women started to become established.