title: Beneficial effects of air inclusions on the performance of ethylene vinyl acetate (EVA) mouthguard material.
abstract: OBJECTIVE
  To investigate the impact characteristics of an ethylene vinyl acetate (EVA) mouthguard material with regulated air inclusions, which included various air cell volumes and wall thickness between air cells. In particular, the aim was to identify the magnitude and direction of forces within the impacts.
  
  
  METHODS
  EVA mouthguard material, 4 mm thick and with and without air inclusions, was impacted with a constant force impact pendulum with an energy of 4.4 J and a velocity of 3 m/s. Transmitted forces through the EVA material were measured using an accelerometer, which also allowed the determination of force direction and magnitude within the impacts.
  
  
  RESULTS
  Statistically significant reductions in the transmitted forces were observed with all the air inclusion materials when compared with EVA without air inclusions. Maximum transmitted force through one air inclusion material was reduced by 32%. Force rebound was eliminated in one material, and reduced second force impulses were observed in all the air inclusion materials.
  
  
  CONCLUSIONS
  The regulated air inclusions improved the impact characteristics of the EVA mouthguard material, the material most commonly used in mouthguards world wide.
authors.affiliation: Clayfield, Queensland, Australia. billwesterman@mgard.com.au
authors.forename: B
authors.initials: B
authors.lastname: Westerman
authors.forename: P M
authors.initials: PM
authors.lastname: Stringfellow
authors.forename: J A
authors.initials: JA
authors.lastname: Eccleston
mesh_terms: D000054:Acceleration; D000388:Air; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008422:Materials Testing; D009064:Mouth Protectors / Q000592:standards*; D011145:Polyvinyls / Q000592:standards*; D011312:Pressure; D019876:Sports Equipment / Q000592:standards*; D013314:Stress, Mechanical
chemical_list: D011145:Polyvinyls; C016438:ethylenevinylacetate copolymer