Electromyographic ratio of masseter and anterior temporalis muscles in children with and without temporomandibular disorders

Abstract Objective This study investigated differences in surface electromyography (sEMG) activity of the masseter and anterior temporalis muscles in children with and without temporomandibular disorders (TMD). Participants Thirty-four children aged 8–12 years were recruited, comprising 17 children with TMD and 17 without TMD (control group [CG]). The children were quasi-matched for sex, age, weight, and height. sEMG data were obtained using Myosystem ® Br-1 equipment with 12 channels to evaluate the bilateral masseter, anterior temporalis, and suprahyoid muscles. For sEMG analysis, raw and normalized root mean square (RMS) values were obtained at rest and during maximum clenching. The sEMG ratios of the raw RMS data of the bilateral masseter in relation to the anterior temporalis muscles (sEMG-M/AT ratio) were also assessed. Mann-Whitney tests (p ≤ 0.05) were used to compare sEMG ratio between TMD group and CG. Results Significant prevalences of pain during chewing (53% vs. 0%, X 2  = 5.87, p = 0.01), TMJ pain (58% vs. 0%, X 2  = 6.67, p = 0.01), neck pain (58% vs. 18%, X 2  = 3.77, p = 0.05) and pain in the temples (47% vs. 6%, X 2  = 5.44, p = 0.02) were identified in the TMD group compared to CG. Our results revealed lower sEMG-M/AT ratios during maximum clenching (p = 0.01) in children with TMD compared to those in the asymptomatic CG. Conclusion The results showed that children with TMD preferentially used their temporalis muscles during maximum voluntary clenching, probably as a consequence of nociceptive inputs in order to obtain pain relief.