title: Relationships between masticatory rhythmicity, body mass and cephalometrically-determined aesthetic and functional variables during development in humans.
abstract: OBJECTIVE
  We studied the relationship between chewing rhythmicity, craniomandibular morphology, and age in humans.
  
  
  METHODS
  Sixty subjects (10M:10F/group×three age groups, viz., 4-8, 10-14, and 17-21 years) participated. Subjects chewed gum for 2min while jaw movements in the frontal plane were videorecorded. Mean and variation in mean chewing cycle duration (TC) were quantified using maximum opening to maximum opening as cycle boundaries. Five "aesthetic" cephalometric variables (e.g., ANB) and seven "functional" variables (e.g., jaw length) were quantified from subjects' lateral cephalographs. Simple linear regression models and several multivariate analyses were used in comparisons.
  
  
  RESULTS
  Mean TC increased and variation in TC decreased significantly with age. Body mass correlated with age, height, TC, all seven "functional" variables and only two "aesthetic" variables. Mean TC was correlated significantly with jaw length, distance from condylion to first molar point, distance from gonion to zygomatic arch, and distance from hyoid to menton.
  
  
  CONCLUSIONS
  TC appeared to adapt with age. Although TC scaled most significantly with age, it is more likely that TC is mechanistically linked to jaw length or size. The decrease in TC variation with age suggests improved efficiency. TC did not scale with "aesthetic" variables, suggesting that these do not impact chewing rate; however, clinical procedures that impact jaw length may. The negative allometric scaling of TC with "functional" variables may reflect the pedomorphic jaw and face of humans. Further human studies will provide insights into the nature of scaling and adaptation of rhythmic chewing during development.
authors.affiliation: Department of Biologic and Materials Sciences, School of Dentistry, 1011 North University, University of Michigan, Ann Arbor, MI 48109-1078, USA; Department of Psychology, University of Michigan, Ann Arbor, MI 48109-1043, USA. Electronic address: geger@umich.edu.
authors.forename: Geoffrey E
authors.initials: GE
authors.lastname: Gerstner
authors.affiliation: Department of Orthodontics and Pediatric Dentistry, School of Dentistry, 1011 North University, University of Michigan, Ann Arbor, MI 48109-1078, USA.
authors.forename: Shashi
authors.initials: S
authors.lastname: Madhavan
authors.affiliation: Department of Biostatistics, M4063 School of Public Health II, 1415 Washington Heights, University of Michigan, Ann Arbor, MI 48109-2029, USA. Electronic address: tombraun@umich.edu.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Braun
mesh_terms: D000293:Adolescent; D000367:Age Factors; D015992:Body Mass Index; D002508:Cephalometry; D002648:Child; D002675:Child, Preschool; D004954:Esthetics; D005260:Female; D006801:Humans; D008297:Male; D008409:Mastication / Q000502:physiology*; D008445:Maxillofacial Development / Q000502:physiology*; D014741:Video Recording; D055815:Young Adult
keywords: Allometry; Cephalometrics; Chewing gum; Development; Mastication; Morphometrics