title: Experimental occlusal interferences. Part II. Masseteric EMG responses to an intercuspal interference.
abstract: In 12 subjects, a rigid unilateral intercuspal interference (minimum mean height of 0.24 mm) was placed on either the right or left mandibular second premolar and first molar (sagittal physiological equilibrium point of the hemimandibular dental arch). During brisk and forceful clenching on the interference, bipolar surface electromyograms were obtained from the right and left masseter muscles. On the side opposite the interference, myoelectric clenching activity was significantly reduced. Correlation analyses showed that the interference elicited a non-linear (complex) co-ordination of the amplitude, but not the duration, of bilateral masseteric clenching activity, i.e. frequently there was significant motor facilitation on the side of the interference, and significant motor inhibition on the side opposite the interference. Theoretical considerations predicted that brief clenching on the interference would easily lead to frontal plane rotatory motions of the mandible which, indeed, occurred clinically.
authors.affiliation: Marquette University, School of Dentistry, Milwaukee, Wisconsin, USA.
authors.forename: L V
authors.initials: LV
authors.lastname: Christensen
authors.forename: N M
authors.initials: NM
authors.lastname: Rassouli
mesh_terms: D000180:Acrylic Resins; D000328:Adult; D001641:Bicuspid; D003769:Dental Occlusion, Traumatic / Q000503:physiopathology*; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008334:Mandible / Q000294:innervation / Q000503:physiopathology; D008406:Masseter Muscle / Q000294:innervation / Q000503:physiopathology*; D008963:Molar; D009046:Motor Neurons / Q000502:physiology; D012399:Rotation; D013997:Time Factors
chemical_list: D000180:Acrylic Resins