Evaluation of integral electromyographic values and median power frequency values in women with myogenous temporomandibular disorder and asymptomatic controls.

Background: Surface electromyography (EMG) has been used as a reliable tool for the evaluation of electrical muscle activity.

Objective: The purpose of this study was to evaluate the EMG indices of the masticatory muscles (masseter, anterior temporalis and suprahyoid) in women with temporomandibular disorder (TMD) and asymptomatic controls in the time domain, by the integrated EMG signal (IEMG) and in the frequency domain, using the median power frequency (MPF).

Methods: An observational, cross-sectional study was conducted involving 30 asymptomatic women as the control (mean age: 25.85 ± 2.57 years) and 74 women with myogenous TMD (mean age: 26.54 ± 2.45 years) diagnosed using the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Three EMG readings were taken during maximum voluntary clenching (MVC) of the molars on parafilm for five seconds with a three-minute rest interval between readings. The mixed-model analysis of variance test followed by the Bonferroni correction or the Student-t test was used for the analyses, with the level of significance set to 5% (p < 0.05).

Results: IEMG values were significantly higher in the masseter muscles than the anterior temporalis muscles in the control group (p < 0.01). IEMG values were significantly higher in the masseter muscles of the control group than the group with myogenous TMD (p < 0.05). MPF values of the suprahyoid muscles were significantly higher in the myogenous TMD group than the control group.

Conclusions: These significant findings show that women with myogenous TMD have reduction of electrical activity of their masseter muscles and increased firing rate of the motor units of the suprahyoid muscles. These findings may help the treatment of myogenous TMD in women.