title: The effects of custom tray material on the accuracy of master casts.
abstract: OBJECTIVE
  The accuracy of master cast reproduction by a polyvinylsiloxane impression material using two visible-light-curing resin and an autopolymerizing polymethyl methacrylate resin custom tray materials was investigated.
  
  
  METHODS
  Custom trays were fabricated from a master cast that had three index points marked on both the inner and outer vestibules. Impressions were made of the master cast using Extrude and then poured in Die Keen Green stone. The distances between the reproduced index points were measured to +/- 0.01 mm with a traveling microscope and the algebraic norms calculated for each tray material.
  
  
  RESULTS
  No differences (p > .05) were found in the dimensions of the inner index points, while the separations of the outer index points indicated that there were differences in the accuracy of reproduction (p < .01) by the three tray materials. The index points reproduced on the casts, compared with the master cast, were closer together for the Triad Blue trays than for the TruTray and Ontray impression trays.
  
  
  CONCLUSIONS
  All three tray materials produced acceptable casts, but the greatest accuracy was achieved with TruTray, followed by Ontray. Triad Blue produced casts that were slightly smaller than the master. In practice, the small measured differences in cast dimensions may not have clinical significance.
authors.affiliation: Baltimore College of Dental Surgery, Dental School, University of Maryland, MD 21201, USA.
authors.forename: L J
authors.initials: LJ
authors.lastname: Martinez
authors.forename: J A
authors.initials: JA
authors.lastname: von Fraunhofer
mesh_terms: D000704:Analysis of Variance; D003760:Dental Impression Materials / Q000737:chemistry*; D003761:Dental Impression Technique / Q000295:instrumentation*; D004548:Elasticity; D005069:Evaluation Studies as Topic; D006801:Humans; D003765:Models, Dental; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011145:Polyvinyls / Q000737:chemistry; D015203:Reproducibility of Results; D012117:Resins, Synthetic / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D014783:Viscosity
chemical_list: D003760:Dental Impression Materials; D011145:Polyvinyls; D012117:Resins, Synthetic; D012833:Siloxanes; C034183:vinyl polysiloxane; D019904:Polymethyl Methacrylate