Masseter muscle thickness three years after surgical correction of class III dentofacial deformity.

Objective: To analyse the effect of integrated orthodontic treatment, orthognathic surgery and orofacial myofunctional therapy on masseter muscle thickness in patients with class III dentofacial deformity three years after orthognathic surgery.

Design: A longitudinal study was conducted on 13 patients with class III dentofacial deformities, denoted here as group P1 (before surgery) and group P3 (same patients 3 years to 3 years and 8 months after surgery). Fifteen individuals with no changes in facial morphology or dental occlusion were assigned to the control group (CG). Masseter muscle ultrasonography was performed in the resting and biting situations in the three groups. Data were analysed statistically by a mixed-effects linear model considering a level of significance of P < 0.05.

Results: Significantly higher values (P < 0.01) of masseter muscle thickness (cm) were detected in group P3 (right rest: 0.82 ± 0.16, left rest: 0.87 ± 0.21, right bite: 1 ± 0.22, left bite: 1.04 ± 0.28) compared to group P1 (right rest: 0.63 ± 0.19, left rest: 0.64 ± 0.15, right bite: 0.87 ± 0.16, left bite: 0.88 ± 0.14). Between P3 and CG (right rest: 1.02 ± 0.19, left rest: 1 ± 0.19, right bite: 1.18 ± 0.22, left bite: 1.16 ± 0.22) there was a significant difference on the right side of the muscle (P < 0.05) in both situations and on the left side at rest.

Conclusion: The proposed treatment resulted in improved masseter muscle thickness in patients with class III dentofacial deformity.