title: The occurrence of spontaneous functional and nonfunctional orofacial activities in subjects without pain under laboratory conditions: a descriptive study.
abstract: OBJECTIVE
  To assess the occurrence and the modality of spontaneous orofacial behaviors of awake healthy subjects without pain who were unaware of bruxism during wakefulness.
  
  
  METHODS
  Sixteen asymptomatic subjects read silently for 30 minutes while polygraphic recordings, including electromyographic (EMG) activity from masticatory and leg muscles, chest respiratory movements, and the movements and sounds of larynx, were made with simultaneous audio-video monitoring. Orofacial behaviors were scored based on the polygraphic and audio-video records. The activity and duration of masseter EMG bursts were calculated for the types of orofacial behaviors.
  
  
  RESULTS
  The number of orofacial behaviors varied between subjects; swallowing was most frequently observed. Approximately half of the orofacial behaviors occurred closely with body movements. Of all masseter EMG bursts detected, 55% were associated with functional orofacial behaviors, while 45% were regarded as nonfunctional. More than 80% of these masseter bursts lasted for less than 2 seconds, with an activity less than 20% of maximal voluntary clenching. These values did not differ between the types of associated orofacial behaviors.
  
  
  CONCLUSIONS
  Although the occurrence of spontaneous orofacial motor activity is variable, asymptomatic subjects can exhibit substantial masseter bursts during wakefulness that are not associated with functional orofacial behaviors. The use of physiological and audio-video records permits spontaneous orofacial behaviors to be specifically identified, thereby allowing nonfunctional masseter EMG activity to be differentiated from functional masseter EMG activity.
authors.affiliation: Institute for Oral Science, Division of Oral and Maxillofacial Biology, Graduate School of Oral Medicine, Matsumoto Dental University, Nagano, Japan. takafumikato@po.mdu.ac.jp
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kato
authors.forename: Shiho
authors.initials: S
authors.lastname: Akiyama
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Kato
authors.forename: Shuichiro
authors.initials: S
authors.lastname: Yamashita
authors.forename: Yuji
authors.initials: Y
authors.lastname: Masuda
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Morimoto
mesh_terms: D000328:Adult; D002012:Bruxism / Q000503:physiopathology; D003371:Cough / Q000503:physiopathology; D003679:Deglutition / Q000502:physiology; D004576:Electromyography; D005149:Facial Expression; D005152:Facial Muscles / Q000502:physiology*; D005260:Female; D006801:Humans; D007830:Larynx / Q000502:physiology; D007866:Leg / Q000502:physiology; D008297:Male; D008406:Masseter Muscle / Q000502:physiology; D008410:Masticatory Muscles / Q000502:physiology*; D008991:Monitoring, Physiologic; D009068:Movement; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D009334:Neck Muscles / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology; D015000:Yawning / Q000502:physiology