title: Influence of color difference of mouthguard sheet on thickness after forming.
abstract: OBJECTIVE
  The aim of this study was to determine the color difference of mouthguard in hardness, water sorption and thickness after forming EVA sheets. Six different colors of sheets were tested for each of three manufacturers.
  
  
  METHODS
  The materials used in this study were mouthguard sheets made by three manufacturers. Each manufacturer supplied six colors: clear, white, yellow, blue, red, and black. Shore A hardness and water sorption were measured based on ISO 7619 and 1817, respectively. The thickness after formation was measured by using a measuring device. The differences in hardness, water sorption and thickness after formation were analyzed by two-way analysis of variance. The correlation between the hardness and changes in thickness was analyzed using Pearson's product-moment correlation coefficient.
  
  
  RESULTS
  Shore A hardness was different depending upon various colored sheets and manufactures. There were differences in the water sorption depending upon some colored sheet among manufacturers. There was a significant difference in the thickness after formation was found to be dependent upon few colors of the sheets on one manufacturer's product on the anterior teeth and on three products on posterior teeth. A negative correlation between the hardness and the change of thickness was found in two products.
  
  
  CONCLUSIONS
  The present study suggests that the Shore A hardness and thickness after formation varied depending upon the colors of the EVA sheets and manufactures. A correlation between the hardness and change of thickness was observed in two manufactures that suggests that the hard sheets tend to reduce in thickness greater than that in softer ones.
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: D000042:Absorption; D003116:Color; D004867:Equipment Design; D006244:Hardness; D008422:Materials Testing; D009064:Mouth Protectors; D013314:Stress, Mechanical; D014867:Water
chemical_list: D014867:Water