Ultrasonographic evaluation of masseter and temporalis muscle thickness and elasticity in individuals with bruxism and bruxism-related myogenous temporomandibular disorders.

OBJECTIVE: To evaluate the thickness and elasticity characteristics of the masseter and temporalis muscles in individuals with probable bruxism and bruxism-related myogenous temporomandibular disorders (TMD) using ultrasonography and ultrasonographic elastography. MATERIALS AND METHODS: This comparative cross-sectional study included 60 patients and 30 healthy controls. Patients were divided into probable bruxism only (Group 1, n = 30) and probable bruxism with myogenous TMD (Group 2, n = 30). Bilateral masseter and temporalis muscle thickness was measured at rest and during maximum contraction. Strain elastography was performed using a tissue phantom reference. Intergroup comparisons were performed using one-way ANOVA with Bonferroni correction. RESULTS: Group 2 demonstrated significantly greater masseter muscle thickness than controls and Group 1, particularly during contraction (p < 0.05). Masseter elasticity ratios were significantly higher in both patient groups than controls, with the highest values in Group 2. During maximum contraction, masseter elasticity ratios were 2.98 ± 1.24 in Group 1, 3.93 ± 2.23 in Group 2, and 2.29 ± 0.87 in controls. Temporalis muscle elasticity values were also significantly increased in Group 2. CONCLUSIONS: Individuals with probable bruxism and bruxism-related myogenous TMD demonstrated differences in masticatory muscle thickness and stiffness, particularly during maximum contraction. Ultrasonography and ultrasonographic elastography may provide complementary information regarding masticatory muscle characteristics and hyperactivity. Given the unadjusted analyses, these findings should be interpreted cautiously. CLINICAL RELEVANCE: Ultrasonography and ultrasonographic elastography may provide useful adjunctive, radiation-free imaging methods for evaluating masticatory muscle alterations in individuals with probable bruxism and bruxism-related myogenous TMD.