title: Effect of mouthguards on the transmission of force across the human jaw.
abstract: OBJECTIVE
  To determine if impact responses (stiffness and damping values) of the jaw and neck are significantly different between mouthguards of varying material and manufacturing properties, in controlled conditions involving specified upper limb orientation and applied loading.
  
  
  METHODS
  Quasi-experimental design.
  
  
  METHODS
  Simon Fraser University biomechanical laboratory.
  
  
  METHODS
  Twelve male subjects between the ages of 19 to 28 participated in this study. All subjects were healthy, had no missing teeth, and had no mechanical (orthodontic) appliances.
  
  
  METHODS
  For each condition, the system stiffness and damping values were estimated using the free vibration technique. Stiffness and damping values are relevant because they are the major determinants of impact force and, potentially, injury risk. It is the first study to show experimentally the quantitative effects of mouthguard in situ.
  
  
  RESULTS
  All the mouthguards lowered the system stiffness as compared with the no mouthguard condition (P < 0.001). There was no observed effect on stiffness between the 2 limb orientation positions. Excitation weight had an unexpected effect on system stiffness (P = 0.041), with increasing weight leading to increased stiffness.
  
  
  CONCLUSIONS
  The findings suggest that wearing any mouthguard is better than wearing none at all due to their ability to reduce system stiffness and damping values after a blow to the chin.
authors.affiliation: Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Lim
authors.forename: Stephen
authors.initials: S
authors.lastname: Robinovitch
authors.forename: David
authors.initials: D
authors.lastname: Goodman
mesh_terms: D000328:Adult; D001265:Athletic Injuries / Q000517:prevention & control*; D001696:Biomechanical Phenomena; D004867:Equipment Design; D006801:Humans; D007568:Jaw; D008297:Male; D009064:Mouth Protectors / Q000145:classification / Q000592:standards; D009333:Neck; D014732:Vibration; D016474:Weight-Bearing / Q000502:physiology