Electromyographic Assessment of Masticatory Muscles & their Asymmetries in Adult Indian Population.

Objective: To study the surface electromyography (sEMG) and it is asymmetry under resting and dynamic conditions in masticatory muscles.

Materials and methods: sEMG of the masticatory muscles (bilateral masseter & temporalis) was done in 61 healthy subjects (mean age 28.5 ± 8.8 years) with bilateral functional molar occlusal relationship. Root mean square (RMS) values sEMG for each activity (rest, clenching, maximum mouth opening (MMO), left and right excursion) for a 10 s period were recorded and analyzed. Indices for asymmetry of muscles, relative activity and resultant torque were assessed and analyzed.

Results: RMS values of sEMG during clenching were significantly higher for all masticatory muscles in males compared to females (p < 0.05). During excursive mandibular movement a statistically significant difference seen in ipsilateral temporalis muscle in males. sEMG of masticatory muscles during rest as well as functional activities of mandible was asymmetrical. A predominant masseteric activity was observed for all functional activities of mandible except during rest for which temporalis muscle activity was higher. Right sided torque was observed during rest, MMO and right lateral movements while a predominant left sided torque was present during left lateral movement and clenching.

Conclusion: sEMG values of masticatory muscles obtained in our study can be used as reference for healthy Indian population. A perfect muscular symmetry might be illusive and a controlled asymmetry criterion appears to be more useful which corresponds to reality.