Is there a difference in the electromyographic activity of the masticatory muscles between individuals with temporomandibular disorder and healthy controls? A systematic review with meta-analysis.

The diagnosis of temporomandibular disorders (TMD) is complex, and it is not yet clear in the literature whether the clinical changes associated with these disorders are also reflected in the electromyographic (EMG) activity of the muscles of mastication. To determine whether there is a difference in the electromyographic activity of the masticatory muscles between individuals with TMD and healthy controls. ScienceDirect, EMBASE, MEDLINE, PEDro, SciELO, CINAHL and LILACS databases from January 2000 to February 2019. Cross-sectional studies, crossover studies and randomised controlled trials evaluating EMG activity of right and left masseter and anterior temporal muscles in patients with TMD and healthy controls. Two independent assessors extracted data from the selected articles. The risk of bias was determined using a checklist for assessing methodological quality created based on the guidelines of the Strengthening the Reporting of Observational Studies in Epidemiology and International Society of Electrophysiology and Kinesiology. Mean differences and 95% confidence intervals were calculated and combined in meta-analyses. A total of 51 267 studies were retrieved, and 12 were included in this review. Only two studies enabled the comparative analysis of the results. The different EMG signal capturing, processing and analysis methods used constitute an important limitation to the comparative analyses of the results reported in the studies selected for the present review. This systematic review did not demonstrate evidence of significant differences in the EMG activity of the masticatory muscles between individuals with TMD and healthy controls.