title: The effects of custom tray material on the accuracy of master casts.
abstract: OBJECTIVE
  In addition to the impression material, the type of impression tray influences the accurate dimensional transfer of the size and position of the teeth to the master cast. The aim of this study was to determine the accuracy of master casts produced from an alginate impression material using a visible-light-curing resin and autopolymerizing polymethyl methacrylate resin custom tray materials.
  
  
  METHODS
  Two types of custom trays were fabricated from a stainless steel master model with three index studs. Twenty-two irreversible hydrocolloid impressions were made of the master model and then poured with a Type III dental stone. The distances between the reproduced index studs were measured to +/- 0.01 mm with a digital caliper. A one-way analysis of variance (ANOVA) and T-test were used for data analysis.
  
  
  RESULTS
  There were no significant differences between the two tray materials for any of the three distances. There were no statistical differences between the master model and the casts made from the two tray materials in the length dimension, but there were significant differences in the vertical dimension. In terms of the width dimension there was a significant difference only between the cold curing group and the master model.
  
  
  CONCLUSIONS
  Within the limitations of this study, the dimensions of stone casts poured from an impression made using a light-cured tray did not differ significantly from those created from impressions made using autopolymerizing acrylic trays. However, working dies from the light-curing tray impressions were more accurate buccolingually than those from the autopolymerizing acrylic trays.
  
  
  CONCLUSIONS
  The accuracy of master cast reproduction using visible-light-curing resin or an autopolymerizing polymethyl methacrylate resin custom tray material is acceptable. Although autopolymerizing resin materials require less equipment and are relatively more inexpensive, light-cure tray materials may be the material of choice for custom tray fabrication due to greater accuracy in the buccolingual dimension.
authors.affiliation: Isfahan University, Iran.
authors.forename: Sina
authors.initials: S
authors.lastname: Shafa
authors.forename: Zeinab
authors.initials: Z
authors.lastname: Zaree
authors.forename: Ramin
authors.initials: R
authors.lastname: Mosharraf
mesh_terms: D000464:Alginates; D003188:Composite Resins / Q000528:radiation effects; D003748:Dental Equipment; D003760:Dental Impression Materials; D003761:Dental Impression Technique / Q000295:instrumentation*; D008027:Light; D008422:Materials Testing; D003765:Models, Dental; D044367:Phase Transition; D019904:Polymethyl Methacrylate / Q000737:chemistry
chemical_list: D000464:Alginates; D003188:Composite Resins; D003760:Dental Impression Materials; D019904:Polymethyl Methacrylate