title: Difference in the thickness of mouthguards fabricated from ethylene-vinyl acetate co-polymer sheets with differently arranged v-shaped grooves.
abstract: OBJECTIVE
  To investigate the form of mouthguard sheets that best retains its thickness.
  
  
  METHODS
  Mouthguards were molded using ethylene-vinyl-acetate (EVA) sheets and a suction-type molding device. Five sheet conditions were compared. These were I-N (Incisal part of the cast positioned at the center - Normal sheet), I-H (Incisal part positioned at the center - Horizontal v-shaped groove 30 mm from the anterior end), I-C (Incisal part positioned at the center - Convexing v-shaped groove toward the back 10-40 mm from the anterior end), C-N (Center part positioned at the center - Normal sheet), and C-C (Center part positioned at the center - Convexing v-shaped groove toward the back 10-30 mm from the anterior end). Post-molding thickness was determined for the incisal (incisal edge and labial surface) and molar portion (cusp, central groove, and buccal surface). Sheets were heated until they sagged 15-mm below the clamp. Scheffé multivariate comparison was performed to compare changes in post-molding thickness among sheet conditions.
  
  
  RESULTS
  Post-molding thickness of mouthguard material differed significantly between the two portions; rates of thickness reduction were smaller for I-C and C-C compared with other conditions. There were no significant differences between I-C and C-C at any measurement points.
  
  
  CONCLUSIONS
  The present results suggested that thickness reduction of the EVA sheet material after vacuum-forming may be decreased at both incisal and molar portions if the v-shaped groove with a v-shaped cross section was given in the frontal teeth region of the sheet at the apparatus and materials for this study used.
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; D009064:Mouth Protectors; D011145:Polyvinyls
chemical_list: D003764:Dental Materials; D011145:Polyvinyls; C016438:ethylenevinylacetate copolymer
keywords: Ethylene-vinyl acetate co-polymer sheet; Mouthguard; Shape of the sheet; Thickness