Effect of transcutaneous electrical nerve stimulation (TENS) on the electromyographic activity of human masticatory muscles in young people with normal occlusion.

ABSTRACT

STATEMENT OF PROBLEM: Transcutaneous electrical nerve stimulation (TENS) has been used in several clinical areas. However, the effect of TENS on the masticatory muscles of young individuals with normal occlusion remains unclear. PURPOSE: The purpose of the study was to assess the effect of TENS on the surface electromyographic (sEMG) activity of masticatory muscles in a young population with normal occlusion. MATERIAL AND METHODS: Twenty residents (5 men and 15 women, mean 24.27 ±2.59 years) of Dalian Stomatological Hospital were enrolled as the study participants. A trained operator collected the required information from the participants. The experiment was divided into 3 stages pre-TENS acquisition, TENS application, and post-TENS acquisition. The pre-TENS stage was performed using surface electromyography (sEMG) (Myotronics Inc) to acquire the potential values of masticatory muscles in the following 3 states 5 times each resting, intercuspal occlusion (ICO), and maximum voluntary clench (clenching). The potential values of the anterior of temporalis (TA), the masseter (MM), the sternocleidomastoid (SCM), and the anterior digastric (DA) muscles were collected in the resting state, and TA and MM were collected in the ICO and clenching states. During the TENS application phase, a TENS Unit device (J5 Myomonitor) (J5) was used on each participant for 45 minutes. The post-TENS acquisition phase involved the same procedure as the pre-TENS phase. The experimental data were recorded, and the normality of each group was analyzed using the Shapiro-Wilk test in a statistical software program (IBM SPSS Statistics, v26.0). The paired-sample t test was used to compare the differences in the mean values of sEMG and the asymmetry index (As); the independent-sample t test was used to compare the activity index (Ac) and torque index (To) (α=.05). RESULTS: Significant differences were observed in the mean potential values of TA, MM, LSCM, and RDA before and after TENS in the resting state and RTA, LMM, and RMM before and after TENS in the clenching state (P<.05). Moreover, although AsDA values showed a significant difference (P=.027) before and after TENS in the resting state, the differences in As values for the other muscles in the resting state were statistically similar. Furthermore, in each state, the mean values of Ac and To after TENS showed no significant differences before and after TENS (P>.05). CONCLUSIONS: The resting EMG values of the TA and MM differed significantly before and after TENS. After TENS, the resting EMG activity decreased, whereas the functional EMG activity tended to increase.