Effects of interocclusal appliances on EMG activity during parafunctional tooth contact

Abstract

To test the hypothesis that a flat plane interocclusal appliance affects the electromyographic (EMG) activity of the temporalis and masseter muscles in pain-free individuals, maxillary splints were fabricated for 20 individuals who reported no history, signs or symptoms of myofascial pain or arthralgia as determined by two trained, independent examiners. Subjects were instructed to establish light tooth contact, maximum clenching, and moderate clenching with/without the splint in place (as determined by random assignment) while EMG data from the left and right temporalis and masseter muscles were recorded. A 5-min biofeedback training session to relax the masticatory muscles was followed by a repetition of the tooth contact/clenching tasks with/without the splint in place. With the splint in place, the activity of the temporalis muscles decreased for all tasks, significantly for the left and right temporalis under maximal clenching and for the right temporalis under moderate clenching. In contrast, the activity of the masseter muscles increased under light and moderate clenching (significantly for the left masseter under moderate clenching) and decreased slightly under maximal clenching. The effectiveness of interocclusal appliances may be due to mechanisms other than redistribution of adverse loading.

Comparison of Habit Reversal and a Behaviorally-Modified Dental Treatment for Temporomandibular Disorders: A Pilot Investigation

“…Studies show that at moderate to minimal levels of bite force, the presence of splints does not significantly reduce and may slightly increase masticatory muscle activity (Lobbezoo et al 1993;Roark et al 2003). An alternative explanation for the efficacy of splints is that ''the mechanism of action by which occlusal appliances [splints] affect ... [pain]... probably is behavioral modification of jaw clenching'' (Kreiner et al 2001, p. 770).…”

“…Patients were then instructed to make contact between the teeth. This action typically increases activity of the temporalis by about 2.5-3.5-fold and of the masseter by 2.0-2.5-fold (Glaros et al 2000;Roark et al 2003), and patients could immediately observe the result of this behavior by watching the computer screen. After a rest, patients were instructed to engage in ''typical'' clenching, increasing EMG activity by at least 10-fold in most patients.…”

Electromyographic study of activity of the masseter and anterior temporalis muscles in patients with temporomandibular joint (TMJ) dysfuction: Comparison with the clinical dysfunction index

“…Recently, electromyographic exploration has been added to this long tests list (4)(5)(6). The theory that the masticatory muscles, in dysfunctional patients, suffer from hypertonicity at rest and fatigue easily when effort is demanded is widely accepted (7)(8)(9). This has given special relevance to the monitoring of muscle activity at rest and during effort in the diagnosis of this pathology.…”

Effect of occlusal splint thickness on electrical masticatory muscle activity during rest and clenching

“…These receptors that are susceptible to external stimuli are sensitized to TMJ, muscles, and periodontal ligaments, as well as regions of the tongue, lips and oral mucosa. 25 Other characteristics of splints that may reduce symptoms associated with TMD are cognitive awareness and the placebo effect. 2 …”