To capture electromyographic signals from the masseter and temporal muscles, a Myosystem-Br1 P84 portable electromyograph (DataHominis Tec. Ltd, Brazil) was used. Differential simple active electrodes and a reference electrode on the wrist consisting of an oval stainless-steel plate, 45 mm long, 30 mm wide, and 1 mm thick, wrapped in plastic, were used.
Before placing the electrodes, the skin was cleaned with alcohol to eliminate grease and pollution residues. The electrodes were positioned by the same trained examiner. To ensure the correct location of the masticatory muscles, specific maneuvers of maximal voluntary contraction were performed, accompanied by digital palpation, according to the recommendations of the surface EMG for non-invasive assessment of muscles (SENIAM) project [12 (link)].
Electromyographic activity (microvolts) was evaluated during mandibular rest (4 s), protrusion (10 s), right laterality (10 s), left laterality (10 s), and dental clenching during maximum voluntary contraction (4 s). During the recording of electromyographic activities, the environment was kept calm and silent, with patients seated in a comfortable chair, upright posture, soles of the feet resting on the ground, and hands resting on the thighs. The head was positioned with the Frankfurt horizontal plane parallel to the ground [13 (link)].
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