ABSTRACT
<p><b>OBJECTIVE</b>To calculate the delay times and embedding dimensions of surface electromyogragh (sEMG) signal of the masseter and temporal muscle during clenching at intercuspal position (ICP), and to reconstruct the space phase of sEMG signal with method of nonlinear dynamics.</p><p><b>METHODS</b>Ten male and 10 female young volunteers with normal masticatory system were included in the study, the signals of surface sEMG of bilateral masseter and temporal muscles in the position of ICP were collected, and the delay times and embedding dimensions of the sEMG signals were calculated using C-C method, the space phase of the sEMG signals was reconstructed.</p><p><b>RESULTS</b>A program of nonlinear dynamic analysis of mastication muscles sEMG signals was developed base on the platform of Matlab. The signals of the sEMG of the masseters and temporals were analyzed with nonlinear dynamic methods, the delay times and embedding dimensions of each muscles sEMG signals were obtained, and the space phase of each sEMG signals were reconstructed. The graphs of the space phase indicated the typical characteristic of chaotic attractor.</p><p><b>CONCLUSIONS</b>The signals of the masseter and temporal muscles of surface sEMG during clenching at ICP of normal masticatory system show the typical characters of chaos, the methods of nonlinear dynamics are effective to analyze the sEMG signals of mastication system.</p>