title: Comparing the Accuracy of Three Different Impression Materials in Making Duplicate Dies.
abstract: BACKGROUND
  Marginal adaptation is very important in cast restorations. Maladaptation leads to plaque retention, reduction of mechanical and esthetic properties. The aim of this study was to evaluate the precision of three different impression materials (including: Additional silicone [AS] and condensational silicone [CS] and polyether [PE]) for duplicating master dies.
  
  
  METHODS
  Three master dies from an acrylic tooth model-with supragingival and shoulder finishing line was made by using PE: Impergum, CS: Speedex, and AS: Panasil separately. The Ni-Cr copings were prepared from master dies separately. They were placed on the acrylic model and the mean marginal difference was recorded by using a stereomicroscope. Then 30 duplicate test dies were made by using the same impression materials and the marginal gaps were recorded. The comparison was done by one-way ANOVA and SPSS software (Version 13) at a significant level of 0.05.
  
  
  RESULTS
  The mean marginal difference of four walls from Impergum (38.56 um) was the lowest than Speedex (38.92 um) and Panasil (38.24 um). The Impergum had the highest capability in making duplicate dies (P > 0.05).
  
  
  CONCLUSIONS
  The Impergum impression material manifested the highest capability in making a better marginal adaptation of duplicate dies but further studies are needed to make a precise decision.
authors.affiliation: Associate Professor, Department of Prosthodontics, Dental Materials Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Farshad
authors.initials: F
authors.lastname: Bajoghli
authors.affiliation: Assistant Professor, Department of Prosthodontics, Dental Implant Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Sabouhi
authors.affiliation: Assistant Professor, Department of Prosthodontics, Dental Implant Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Saeid
authors.initials: S
authors.lastname: Nosouhian
authors.affiliation: Dentistry Student, Dental Students Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Amin
authors.initials: A
authors.lastname: Davoudi
authors.affiliation: Dentist, Torabinejad Dental Research Center, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Zeynab
authors.initials: Z
authors.lastname: Behnamnia
keywords: Dimensional changes; duplicate dies; impression materials; marginal adaptation