ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of the biofeedback in regulating the myoelectric activities of the masseter muscles.</p><p><b>METHODS</b>Twenty orthodontic patients aged from 10 to 14 years with Angle Class II malocclusion, retrusive mandible, and an ANB angle > 6° were enrolled in this study. The muscular activities of the anterior temporal muscle and the masseter muscle were evaluated before, during, and after biofeedback treatment by assessing the average integrated electromyogram and temporal/masseter (T/M) ratio in the clenching status.</p><p><b>RESULTS</b>The patients' myoelectric activities of the anterior temporal muscle was significantly increased after biofeedback treatment (P<0.05). The patients' T/M ratio in the clenching status was increased after the treatment (1.76 ± 1.46 before treatment, 4.71 ± 4.03 immediately after treatment, and 2.57 ± 2.07 at 1 day after treatment; t=4.86, P<0.05).</p><p><b>CONCLUSION</b>Biofeedback treatment can regulate the activities of the anterior temporal and masseter muscles and increase the T/M ratio in the clenching status.</p>