title: Dimensional accuracy of 7 die materials.
abstract: OBJECTIVE
  The purpose of this study was to compare the linear dimensional accuracy and the handling characteristics of 7 die materials.
  
  
  METHODS
  A master die analogous to a complete veneer crown preparation was machined from medical grade stainless steel, and 3 measurements (1: vertical; 2 and 3: horizontal) were made from 3 scribed reference lines. Individual polyvinylsiloxane impressions were made (n = 10) for each of the specimens. The fabricated dies were measured (50x) to the nearest 0.0001 mm. Data were subject to ANOVA/Duncan tests at significance level 0.05 and pairwise comparisons.
  
  
  RESULTS
  Type IV resin-impregnated dental stone and copper-plated dies most closely approximated the dimensions of the master die, and were not significantly different from each other in any of the pairwise comparisons. Conventional Types IV and V dental stone dies exhibited setting expansion within the range appropriate for gypsum. Epoxy resin die materials demonstrated shrinkage comparable to the expansion of the Types IV and V dies. Polyurethane dies displayed a combination of linear expansion and shrinkage. Bis-acryl composite resin dies had excessive shrinkage.
  
  
  CONCLUSIONS
  Type IV resin-impregnated dental stone and copper-plated dies were more dimensionally accurate than the other die materials tested.
authors.affiliation: Department of Restorative Dentistry, University of the Pacific School of Dentistry, San Francisco, CA 94115, USA. bkenyon@sf.uop.edu
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Kenyon
authors.forename: Mark S
authors.initials: MS
authors.lastname: Hagge
authors.forename: Casimir
authors.initials: C
authors.lastname: Leknius
authors.forename: Walter C
authors.initials: WC
authors.lastname: Daniels
authors.forename: Scott T
authors.initials: ST
authors.lastname: Weed
mesh_terms: D002133:Calcium Sulfate; D003188:Composite Resins; D003300:Copper; D003442:Crowns; D003722:Dental Alloys; D004853:Epoxy Resins; D008422:Materials Testing; D003765:Models, Dental; D015203:Reproducibility of Results
chemical_list: D003188:Composite Resins; D003722:Dental Alloys; D004853:Epoxy Resins; D003300:Copper; D002133:Calcium Sulfate