Electromyographic and Anthropometric analysis of patients with temporomandibular disorders

Objectives: To examine symmetry/asymmetry and potential lateral displacing of the jaw in patients with TMD, as compared to those of healthy subjects
Methods: Thirty-six subjects, 22 patients with symptoms related to TMD ranging of light to severe (TMD group, mean age 29.7 years, SD 5.2, 5 man and 17 women) and 14 subjects without signs or symptoms of TMD (Control group, mean age 24.3 years, SD 3.6, 2 men and 12 women) participated in the study. Surface EMG of masseter and temporal muscles was performed during maximum teeth clenching either on cotton rolls or in intercuspal position, both for 5 seconds. The following standardized EMG indices were obtained: percentage overlapping coefficient (POC, unit: %) to assess right-left muscle symmetry, and potential lateral displacing components given by unbalanced contractile activities of contralateral masseter and temporal (TORS, unit %); these indices range between 0 (no symmetry or maximum lateral displacing force) and 100% (perfect symmetry or absence of lateral displacing force). Anthropometric measures were performed (Laserscan), based on landmarks Exacanthion (Ex), Cheilion (Ch), Tragus (T), right and left, in order to examine the percentual asymmetry between sides for linear distances and curvatures. The test T-student was used for group comparisons (p < 0.05).
Results: TMD patients showed significantly larger unbalanced contractile activities of contralateral masseter and temporal muscles (TORS) than Control group (mean±SD= 89.0±3.4% x 91.7±0.8%) (p<0.05, t-test). In the present study there is no statistical difference related symmetry/asymmetry between groups either on EMG or in anthropometric measures.
Conclusions: Patients with TMD with symptoms ranging of light to severe showed more unbalanced contractile activities of contralateral masseter and temporal muscles than Control subjects, but no physiologic (EMG) or morphologic asymmetry between right-left sides.