title: 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.
authors.affiliation: Department of Stomatology, University of Santiago de Compostela, Spain.
authors.forename: U
authors.initials: U
authors.lastname: Santana-Mora
authors.forename: J
authors.initials: J
authors.lastname: Cudeiro
authors.forename: M J
authors.initials: MJ
authors.lastname: Mora-Bermúdez
authors.forename: B
authors.initials: B
authors.lastname: Rilo-Pousa
authors.forename: J C
authors.initials: JC
authors.lastname: Ferreira-Pinho
authors.forename: J L
authors.initials: JL
authors.lastname: Otero-Cepeda
authors.forename: U
authors.initials: U
authors.lastname: Santana-Penín
mesh_terms: D000293:Adolescent; D018771:Arthralgia / Q000209:etiology / Q000503:physiopathology*; D002012:Bruxism / Q000150:complications / Q000503:physiopathology*; D002908:Chronic Disease; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008410:Masticatory Muscles / Q000503:physiopathology*; D009119:Muscle Contraction; D013705:Temporomandibular Joint Disorders / Q000150:complications / Q000503:physiopathology*; D055815:Young Adult