title: Analysis of temporal variation in human masticatory cycles during gum chewing.
abstract: OBJECTIVE
  The study investigated modulation of fast and slow opening (FO, SO) and closing (FC, SC) chewing cycle phases using gum-chewing sequences in humans.
  
  
  METHODS
  Twenty-two healthy adult subjects participated by chewing gum for at least 20s on the right side and at least 20s on the left side while jaw movements were tracked with a 3D motion analysis system. Jaw movement data were digitized, and chewing cycle phases were identified and analysed for all chewing cycles in a complete sequence.
  
  
  RESULTS
  All four chewing cycle phase durations were more variant than total cycle durations, a result found in other non-human primates. Significant negative correlations existed between the opening phases, SO and FO, and between the closing phases, SC and FC; however, there was less consistency in terms of which phases were negatively correlated both between subjects, and between chewing sides within subjects, compared with results reported in other species.
  
  
  CONCLUSIONS
  The coordination of intra-cycle phases appears to be flexible and to follow complex rules during gum-chewing in humans. Alternatively, the observed intra-cycle phase relationships could simply reflect: (1) variation in jaw kinematics due to variation in how gum was handled by the tongue on a chew-by-chew basis in our experimental design or (2) by variation due to data sampling noise and/or how phases were defined and identified.
authors.affiliation: Department of Biologic and Materials Sciences, School of Dentistry, Ann Arbor, MI 48109-1078, USA. bcrane@umich.edu
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Crane
authors.forename: Edward D
authors.initials: ED
authors.lastname: Rothman
authors.forename: David
authors.initials: D
authors.lastname: Childers
authors.forename: Geoffrey E
authors.initials: GE
authors.lastname: Gerstner
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D002638:Chewing Gum; D005260:Female; D006801:Humans; D008297:Male; D008409:Mastication / Q000502:physiology*; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D009068:Movement / Q000502:physiology; D013997:Time Factors
chemical_list: D002638:Chewing Gum
keywords: Chewing cycles; Gape cycles; Kinematics; Mastication