Eletromiografia em repouso e força de mordida como marcadores funcionais da Disfunção Temporomandibular: revisão sistemática com metanálise

Abstract

Introduction: Temporomandibular disorder (TMD) is a common condition that affects the temporomandibular joint and the masticatory muscles, leading to pain, dysfunction, and neuromuscular alterations. Quantitative parameters such as bite force and resting electromyography (EMG) have been proposed as potential functional markers, but existing evidence still presents inconsistent results. Objective: To investigate whether bite force and resting electromyographic activity of the masseter muscle differ between adults with and without temporomandibular disorder. Methods: Systematic review with meta-analysis registered in PROSPERO, conducted in accordance with PRISMA guidelines and the Cochrane Handbook. The search was performed in PubMed, Scopus, Web of Science, LILACS/MEDLINE, and SciELO databases, with no language restrictions. Analytical crosssectional observational studies comparing adults with and without TMD were included. Methodological quality and risk of bias were assessed using the JBI and AXIS tools, and the strength of the evidence was classified using the GRADE approach. The qualitative variables were described in the table of clinical and methodological characteristics of the included studies. The meta-analysis was conducted using a random-effects model. Results: Twenty studies were included in the systematic review. Among them, only three presented sufficiently homogeneous and complete data for inclusion in the meta-analysis. One study contributed simultaneously to both outcomes, resulting in the inclusion of two studies for the bite force analysis (n = 164) and two for the resting electromyographic (EMG) activity of the masseter muscle (n = 177). Bite force was significantly lower in the TMD group (SMD = -2.74; 95%CI: -4.72 to -0.76; p = 0.007; I² = 95%), and resting EMG activity was significantly higher in this group (SMD = -1.03; 95%CI: -1.35 to -0.72; p < 0.00001; I² = 75%). The qualitative analysis of the remaining studies revealed that methodological quality ranged from moderate to high, risk of bias from low to moderate, and the strength of evidence from very low to moderate. Conclusion: Adults with TMD showed reduced bite force and increased resting electromyographic activity of the masseter in the included studies. These findings suggest the potential of these parameters as functional markers. Due to the limited number of studies included in the meta-analysis, methodological heterogeneity, and the fragility of the evidence, the results should be interpreted with caution. Future studies with greater standardization and methodological rigor are needed to confirm these findings.