An electromyographic investigation of masticatory muscles symmetry in normo-occlusion subjects

The influence of occlusal conditions on symmetric muscles). Waveforms were also analysed stomatognathic function can be assessed by elec- for a laterodeviating effect on the mandible given tromyography. Electromyographic activity of left by unbalanced muscular couples, and a torque coand right temporal and masseter muscles was efficient (up to 100% for a significant laterodeviatrecorded in 30 young healthy adults with a normal ing couple on the mandible) was computed. In all occlusion during: (1) a 3-s maximum voluntary subjects, both tests were performed with symmetclench on cotton rolls positioned on the posterior ric muscular patterns (more than 88%) and with teeth (standardization recording); (2) a 3-s maxi- negligible laterodeviating couples on the mandible mum voluntary clench in intercuspal position; and (lower than 10%). The two coefficients allow an (3) a 3-s alternate ‘maximum’ voluntary contraction assessment of muscular asymmetry during static and relaxation with a 1 Hz frequency. All potentials and dynamic clenching tests, and, together with the were standardized as a percentage of the maximum standardization of the potentials, could be a useful potential of test 1. Waveforms of paired muscles tool to detect functionally altered occlusal condiwere compared by computing a percentage overlap- tions, i.e. conditions where an apparent good morping coefficient (ratio between each 50-ms over- phological situation is not related to a correct lapped areas and the total areas, up to 100% for neuromuscular status.