title: Laterotrusive occlusal schemes and jaw posture tasks effects on supra- and infrahyoid EMG activity in the lateral decubitus position.
abstract: The purpose of this study was to determine the effect of canine guidance and group function on supra- and infrahyoid EMG activity in the lateral decubitus position at different jaw posture tasks. The sample included 40 healthy subjects with natural dentition and bilateral molar support, 20 with bilateral canine guidance and 20 with bilateral group function. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the left supra- and infrahyoid muscles for EMG recordings. In the lateral decubitus position, EMG activity was recorded in subjects with canine guidance or group function, during the following jaw posture tasks: A. maximal clenching in the edge-to edge lateral contact position; B. grinding from intercuspal position to edge-to-edge lateral contact position, and C. grinding from edge-to-edge lateral contact position to intercuspal position. Supra- and infrahyoid EMG activity was not significantly different with canine guidance or group function (mixed model with unstructured covariance matrix). Overall comparison of suprahyoid or infrahyoid EMG activity among the three jaw posture tasks studied showed a significantly higher activity during jaw posture task A (clenching) than jaw posture tasks B and C (grinding). Suprahyoid EMG activity was significantly higher during jaw posture task C than B, whereas infrahyoid EMG activity did not present a significant difference between jaw posture tasks C and B. These EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding. The neurophysiological mechanisms involved are discussed.
authors.affiliation: Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile, Independencia 1027, Clasificador NO 7, Independencia, Santiago, Chile. rmiralle@med.uchile.cl
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Miralles
authors.forename: Francisca
authors.initials: F
authors.lastname: Gallardo
authors.forename: Mauricio
authors.initials: M
authors.lastname: Baeza
authors.forename: Saúl
authors.initials: S
authors.lastname: Valenzuela
authors.forename: María José
authors.initials: MJ
authors.lastname: Ravera
authors.forename: Guillermo
authors.initials: G
authors.lastname: Ormeño
authors.forename: Gabriel
authors.initials: G
authors.lastname: Cavada
mesh_terms: D000293:Adolescent; D000328:Adult; D002012:Bruxism / Q000503:physiopathology; D003766:Dental Occlusion; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D007568:Jaw / Q000502:physiology*; D008297:Male; D009334:Neck Muscles / Q000502:physiology*; D011187:Posture; D012044:Regression Analysis