The effect of electrical stimulation of the temporalis muscles on orofacial pain in patients with bruxism symptoms

Aim: The objective of the present study was to investigate the effect of biofeedback treatment, administered via contingent electrical stimulation (CES) with the GrindCare 4 device (market launch in 2016), on bruxism activity and orofacial pain in patients with temporomandibular disorders (TMD) and bruxism.
Materials and methods: Twenty-six participants were enrolled in this follow-up study. The first 13 (group 1) completed a 21-day study protocol. The next 13 (group 2) were assigned a 42-day protocol, which 10 participants completed successfully. The study was conducted in three phases. In phase 1 (pretreatment), participants received baseline functional status (Research Diagnostic Criteria for Temporomandibular Disorders [RDC/TMD] questionnaire and clinical examination) and bruxism status examinations (Lange & Bernhardt Bruxism Status screener) and were then supplied with study information and a GrindCare 4 device, with oral and written instructions for its use. Per protocol, participants were directed to use the device without biofeedback on the first 4 or 7 nights, respectively, for a baseline measurement of jaw muscle contraction frequency. In phase 2 (treatment), they were to activate the device’s biofeedback mode and administer themselves after 2 to 4 weeks, respectively, of CES treatment. In phase 3 (posttreatment), group 1 and 2 participants used GrindCare 4 without biofeedback on 3 or 7 nights, respectively, for follow-up measurement and evaluation of jaw muscle contraction frequency, followed by a second functional status assessment (RDC/TMD questionnaire and clinical examination).
Results: A significant reduction of bruxism events was only achieved after 4 weeks of CES (42-day study protocol): compared with pretreatment measurements (baseline), the number of bruxism events was 40% lower after 4 weeks of treatment and 32% lower during posttreatment follow-up. The number of painful palpation sites decreased significantly in both groups (21-day arm: P = 0.010; 42-day arm: P = 0.035). However, no significant change in pain intensity was detected.
Conclusions: A 2-week CES intervention appears to be insufficient because a reduction of bruxism events only occurred after a longer treatment duration. The reduction of bruxism events achieved by 4 weeks of CES persisted into the posttreatment follow-up phase, suggestive of a potential learning effect. No evidence was found of a reduction of bruxism symptoms. At the time of publication, the manufacturer had withdrawn the study device from the market for modification. Further controlled studies with larger cohorts are needed to verify these results. A longer treatment duration and follow-up would be advisable.