title: Specific increase in non-functional masseter bursts in subjects aware of tooth-clenching during wakefulness.
abstract: Previous studies have reported that subjective awareness of a tooth-clenching habit is associated with increased jaw motor activity (Rao SM, Glaros AG, J Dent Res. 1979;58:1872). The aim of this study was to test the hypothesis that subjects with clenching awareness exhibit different motor expressions specific to non-functional oromotor activity under laboratory conditions without psychological or sensory effects. Polygraphic and audio-video recordings were made for a 30-min period of silent reading by 33 subjects without oro-facial pain. Oro-facial behaviours (e.g. swallowing, lip movements) were scored according to the polygraphic and audio-video records and masseter bursts were quantitatively analysed. Subjective psychological/sensory measures were also recorded before and/or after the polygraphic recording using a visual analogue scale. The subjects were classified into two groups one with 15 subjects who were aware of having a tooth-clenching habit and another with 18 who were not aware of any such habit. There were no differences between the groups with respect to the number of functional oro-facial behaviours or subjective psychological/sensory measures. Masseter bursts unrelated to functional oro-facial behaviours occurred more frequently in subjects with awareness [median (range) = 23 (2-187) bursts] than in those without [9.0 (0-36); P = 0.01], while neither burst activity [12.3 (1.8-34.5) % of maximum voluntary clenching and 10.1 (6.5-25.1) %, respectively] nor duration [1.17 (0.2-2.2) s and 1.28 (0.3-4.1) s, respectively] differed between the groups. The occurrence of functional oro-facial behaviours or other body behaviours (e.g. limb and body movements) did not differ between the two groups. These findings suggest that the increased masseter activity in subjects with tooth-clenching awareness is characterized by a specific increase in non-functional masseter bursts.
authors.affiliation: Department of Fixed Prosthodontics, Matsumoto Dental University, Nagano, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Katase-Akiyama
authors.forename: T
authors.initials: T
authors.lastname: Kato
authors.forename: S
authors.initials: S
authors.lastname: Yamashita
authors.forename: Y
authors.initials: Y
authors.lastname: Masuda
authors.forename: T
authors.initials: T
authors.lastname: Morimoto
mesh_terms: D056044:Actigraphy; D000328:Adult; D000704:Analysis of Variance; D002012:Bruxism / Q000503:physiopathology*; D004576:Electromyography; D005260:Female; D006801:Humans; D007568:Jaw / Q000502:physiology*; D008297:Male; D008406:Masseter Muscle / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D014743:Videotape Recording; D014851:Wakefulness; D055815:Young Adult