Changes in EMG activity during clenching in chronic pain patients with unilateral temporomandibular disorders

Abstract

The study assessed the differences in electromyographic (EMG) activity recorded during clenching in women with chronic unilateral temporomandibular disorders (TMDs) as compared to control subjects. Seventy-five full dentate, normo-occlusion, right-handed, similarly aged female subjects were recruited. Twenty five subjects presented with right side TMD, 25 presented with left side TMD and 25 pain-free control subjects participated. Using integrated surface EMG over a 1 s contraction, the anterior temporalis and masseter muscles were evaluated bilaterally while subjects performed maximum voluntary clenching. Lower EMG activation was observed in patients with TMD as compared to control subjects (temporalis: 195.74+/-18.57 vs. 275.74+/-22.11, P=0.011; masseters: 151.09+/-17.37 vs. 283.29+/-31.87, P<0.001). An asymmetry index (SAI) was calculated to determine ratios of right to left sided activation. Patients with right-sided TMD demonstrated preferential use of their left-sided muscles (SAI -5.35+/-4.02) whereas patients with left-sided TMD demonstrated preferential use of their right-sided muscles (SAI 6.95+/-2.82), (P=0.016). This unilateral reduction in temporalis and masseter activity could be considered as a specific protective functional adaptation of the neuromuscular system due to nociceptive input. The asymmetry index (SAI) may be a useful measure in discriminating patients with right vs. left-sided TMD.

Diagnostic tests for temporomandibular disorders 81

“…This patient's response mirrors which has been reported in many published ICAGD studies and Clinical reports, [6][7][8][9][10]29,31] since the inception of the T-scan I technology in the mid 1980's, [14,15] such that treating the myofascial pain dysfunction with ICAGD is not new. Lengthy DT has been shown in EMG studies to elevate excursive muscle activity levels, and that proper reduction of the DT to <0.4 s, can reduce the muscle hyperactivity and related myofascial pain symptoms.…”

“…Lengthy DT has been shown in EMG studies to elevate excursive muscle activity levels, and that proper reduction of the DT to <0.4 s, can reduce the muscle hyperactivity and related myofascial pain symptoms. [8,9,29] The beauty of this computer-guided treatment approach is that it lessens hyperactive muscles from within the central nervous system, by controlling the molar periodontal ligament (PDL) mechanoreceptors, which synapse directly with efferent motor fibers that contract the four masticatory muscles. [16] Prolonged excursive frictional contacts increase the total time PDL mechanoreceptors are compressed in excursive movements, where the PDL compression time is equal to the DT duration of that same excursion.…”

“…[32] The more time the excursive interferences contact, the longer time the PDL are compressed, resulting in prolonged durations of masticatory muscle contractions. [8,9,29] By reducing the length Post-treatment right lateral -time to muscle shut down shorter from immediate complete anterior guidance development enameloplasty 1.5 s of time, the posterior occlusal surfaces contact excursively, the volume and duration that PDL mechanoreceptors are reduced, thereby interrupting the PDL compression-to-muscle hypercontraction. Post ICAGD, the PDL no longer hyper functions the involved muscles into a painful ischemic state, allowing for re-oxygenation and muscle fiber recovery, leading to symptom resolution without the patient wearing an appliance, undergoing TENS, taking pain, muscle relaxant, or anti-inflammatory medications, or requiring trigger point and/or Botox injections.…”

“…These are outside of the known physiologic ranges (physiologic OT ≤0.2 s; DT <0.4 s). [11,29] Of note is that the time to muscle shut down [10] of the working temporalis muscles in Figures 5 and 6 ranges between 2 and 3 s, which is far too long to be physiologic. This prolonged muscle firing is a major contributor to the Occluso-muscular symptoms the patient experiences.…”

Surface electromyographic assessment of patients with long lasting temporomandibular joint disorder pain

“…Patients with temporomandibular joint disorders (TMD) are becoming a considerable part of the patients referred to dental clinics (Epker et al, 1999;Iwasaki et al, 2010;Murray and Peck, 2007;Santana-Mora et al, 2009). In these patients, pain and disability are not confined to the stomatognathic system, negatively influencing the global quality of life (De Felício et al, 2009;Dworkin and LeResche, 1992;Epker et al, 1999;Iwasaki et al, 2010;Santana-Mora et al, 2009).…”