title: Variation in mouthguard thickness due to different heating conditions during fabrication.
abstract: OBJECTIVE
  The aim of this study was to evaluate the change in thickness of the mouthguard sheet due to different heating conditions during fabrication.
  
  
  METHODS
  Mouthguards were fabricated with ethylene vinyl acetate (EVA) sheets (4.0-mm thick) using a vacuum-forming machine, and six conditions which varied the height of the frame above the surface, reversing the sheet while heating, and controlled power on-off of the heater when a specified level of sagging had been attained were used to determine optimal conditions. The working model was trimmed to a height of 20-mm at the incisor and 15-mm at the first molar. Post-molding thickness was determined for the incisal portion (incisal edge and labial surface) and molar portion (cusp, central groove, and buccal surface). Differences in the change in thickness due to heating condition were analyzed using Scheffé's multiple comparison tests.
  
  
  RESULTS
  The heating condition which the sheet frame was lowered to and heated at 50mm below the top of the post, the heater was turned off when the sheet sagged by 10mm, and the sheet was molded when the sagging reached 15 mm showed the thickest, what the decrease in the thickness reduction was approximately 0.40-0.44 mm at the incisal, and that was 0.35-0.40 mm at the molar portions.
  
  
  CONCLUSIONS
  When molding a mouthguard using an EVA sheet, the thickness of the incisal and molar portions of the mouthguard can be maintained by adjusting the height of the sheet frame and heating conditions, which may be clinically useful.
authors.affiliation: Department of Removable Prosthodontics, The Nippon Dental University School of Life Dentistry at Niigata, Japan. mutsumit@ngt.ndu.ac.jp
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Takahashi
authors.forename: Kaoru
authors.initials: K
authors.lastname: Koide
authors.forename: Fumi
authors.initials: F
authors.lastname: Mizuhashi
mesh_terms: D003764:Dental Materials; D004867:Equipment Design / Q000379:methods*; D006358:Hot Temperature; D003765:Models, Dental; D009064:Mouth Protectors; D011145:Polyvinyls
chemical_list: D003764:Dental Materials; D011145:Polyvinyls; C016438:ethylenevinylacetate copolymer
keywords: Ethylene vinyl acetate co-polymer sheet; Heating conditions; Mouthguard; Thickness