Grindcare^® Stimulation in Myofascial TMD: Effect on Bruxism and Pain

Objective: Nocturnal bruxism has been widely implicated in the onset and persistence of painful myofascial temporomandibular disorders (M/TMDs).  Recent polysomnographic evidence has challenged prevailing theory that bruxism  / hyperactive masticatory muscle activity causes painful myofascial TMD.  The equivocal causal relationship between bruxism and M/TMD further questions the efficacy of common treatments purported to reduce muscle activity and/or relieve pain such as oral appliances and muscle relaxant medication. This mechanistic clinical trial explored the relationships between oromotor hyperactivity and masticatory muscle pain following a treatment intervention (Grindcare^®; Medotech A/S) that has been shown to reliably reduce masticatory EMG.

Method: 14 women (mean age 34.9y (SD 11.5, range 24-64)) with M/TMD and prior polysomnographic evidence consistent with sleep bruxism participated in a 10 week single group pre-test post-test mechanistic clinical trial. Two weeks of baseline monitoring of individually biocalibrated EMG events associated with sleep bruxism was followed by 6 weeks of EMG-event-contingent treatment via an innocuous electrical pulse to the skin overlying the temporalis muscle. Treatment was discontinued during 2-week follow-up monitoring. Each night before sleep, subjects recorded their average daily pain.

Result: Mixed model analysis of variance showed a reliable reduction of EMG events during contingent stimulation treatment periods, but frequency of EMG events returned to baseline levels during follow-up (linear term, p=.002, quadratic term p=.001). In contrast, nightly pain reports failed to show any systematic changes during treatment (linear and quadratic trends, both p>.10). Thus, while the data demonstrated a significant relationship between Grindcare^®  treatment and reduced EMG events, there was no evidence to support any change in nightly pain reports. 

Conclusion: Spontaneous pain severity and nighttime oromotor activity vary independently over nights, even in M/TMD patients selected for relatively high levels of both characteristics.   Our data indicates that Grindcare^® does NOT reduce painful M/TMD, but does reduce nocturnal oromotor activity.