Purpose
This study aimed to compare the time of masseter and anterior temporal muscle activations, in different ranges of surface electromyographic amplitude, between controls and individuals with temporomandibular disorders (TMDs) during mastication.
Methods
Twenty-two female patients, aged 18-48 years, were divided into the TMD group (n=14; TMD type Ia, according to the Research Diagnostic Criteria for Temporomandibular Disorders) and the control group (n=8; non-diagnosed and asymptomatic individuals). Time and surface electromyography (SEMG) amplitudes from the anterior temporal and masseter muscles were registered during bilateral chewing of Parafilm M® for 10 s. SEMG amplitudes were categorized as 0-39%, 40-74%, and 75-100% of the mean of three maximal clenchings. The percentages of total activation times (duty factor) in each range of SEMG amplitudes were compared between groups using an unpaired Student’s t-test.
Results:
There were no differences in duty factor comparisons between groups.
Conclusion:
The activation time of the masticatory muscles was not found to be shorter in the TMD patients than in the controls. Finally, the application of the electromyographic variable proposed in this study may not be considered useful to diagnose type Ia TMD in clinical practice. However, its application may be complementary to the history and physical examination of these patients.
Electromyography; Masticatory muscles; Temporomandibular Joint Dysfunction Syndrome; Mastication; Muscle contraction
