Masseter muscle thickness increases after mandibular setback surgery.
After mandibular set-back, the internal echogenic pattern of the masseter muscle changes.
There was no relationship between the amount of movement performed on the mandible and the changes in the masseter muscle.
The masseter muscle is one of the structures that undergoes significant changes following jaw movements in orthognathic surgery. This study aims to investigate the effects of mandibular setback surgery, performed in patients with skeletal class III deformity, on the thickness, width, elasticity index, and echogenic pattern of the masseter muscle.
Material and methods
This prospective case-control study enrolled patients with class III deformity who underwent mandibular setback surgery, while the control group consisted of class I patients. The predictor variable was the time measured at two different points: preoperative (T1) and postoperative 6 months (T2). The primary outcome variable focused on changes in the internal echogenic pattern of the masseter muscle. Secondary, tertiary, and quaternary outcome variables included changes in the thickness, width, and elasticity index of the masseter muscle, respectively. Gender, age, type of operation, and amount of movement were considered as covariates. Ultrasonography was employed to evaluate the outcome variables.
The study group comprised 31 patients, including 17 females (mean age 22.24 ± 3.52 years) and 14 males (mean age 23.14 ± 2.65 years). The control group consisted of 16 females (mean age 23.34 ± 1.22 years) and 15 males (mean age 23.12 ± 1.76 years). Masseter muscle thickness increased significantly after mandibular setback surgery (p = 0.015). However, there was no statistically significant difference in masseter muscle width before and after surgery (p = 0.627), nor in the elasticity index (p = 0.588). Furthermore, a statistically significant transformation from Type I to Type II was observed in the internal echogenic pattern of the muscle (p = 0.039). Additionally, there was no statistically significant correlation between the amount of mandibular movement performed and the changes in the masseter muscle.
Mandibular setback surgery leads to changes in both the physical and structural properties of the masseter muscle.Le texte complet de cet article est disponible en PDF.
Keywords : Orthognathic surgery, Masseter muscle, Malocclusion, Angle class III/surgery, Ultrasonography