title: Dimensional accuracy of an epoxy die material using different polymerization methods.
abstract: OBJECTIVE
  Shrinkage of resinous die materials during setting reaction limits their acceptance, even though these materials show several advantages compared to stone die materials with respect to strength, abrasion resistance, and detail reproduction. The purpose of this study was to determine if retarding the setting reaction during polymerization and altering the base-to-catalyst ratio, as suggested by previous studies, can be recommended for resinous die materials to reduce the inaccuracy in transferring the spatial position of teeth or implants from the oral cavity to the master cast.
  
  
  METHODS
  A Blue Star Type E epoxy resin die material was tested. A reference triangular metal master die was fabricated. Forty medium-consistency polyether impressions of this model were made. Four groups (S, M, N, P) were compared, and ten dies were fabricated for each group. In the S group, the epoxy resin die material was manipulated according to the manufacturer's instructions; in the other three groups, the epoxy resin die material was manipulated by retarding the setting reaction and by modifying the epoxy resin base/activator ratio.
  
  
  RESULTS
  One-way ANOVA revealed significant differences between the four groups of the epoxy resin die material (p < 0.0001). Tukey's multiple comparisons test (p < 0.05) revealed that none of the resin groups was similar to the metal master die for each of the tested dimensions (A, B, and C). For the specific dimension C, however, the P group was statistically closer to the metal master die than the S group.
  
  
  CONCLUSIONS
  The epoxy resin die material tested in this research did not improve its dimensional accuracy following retarding polymerization or modifying the epoxy resin base/activator ratio. The epoxy resin material exhibited higher contraction variability across all tested groups. This shrinkage can significantly affect the dimension of the master cast.
authors.affiliation: Department of Clinical Odontostomatology, University of Padova, Institute of Clinical Dentistry, Padova, Italy.
authors.forename: Rosario
authors.initials: R
authors.lastname: Prisco
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Cozzolino
authors.forename: Paolo
authors.initials: P
authors.lastname: Vigolo
mesh_terms: D003734:Dental Casting Investment / Q000737:chemistry*; D003735:Dental Casting Technique; D003760:Dental Impression Materials / Q000737:chemistry; D003761:Dental Impression Technique; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D004853:Epoxy Resins / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D003765:Models, Dental; D011108:Polymers / Q000737:chemistry; D013499:Surface Properties
chemical_list: D003734:Dental Casting Investment; D003760:Dental Impression Materials; D003764:Dental Materials; D004853:Epoxy Resins; D011108:Polymers