title: Internal and marginal fit of cobalt-chromium fixed dental prostheses fabricated with 3 different techniques.
abstract: BACKGROUND
  Conventionally, the fabrication method for Co-Cr restorations has been casting by the lost-wax method. Milling and selective laser melting (SLM) are more cost effective and thereby increasingly used. The precision of the different methods regarding internal and marginal fit, however, is not fully known.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to examine and evaluate whether the 3 fabrication methods of conventional casting, milling, and SLM differ in internal and marginal fit for Co-Cr fixed dental prostheses (FDPs).
  
  
  METHODS
  Thirty Co-Cr metal frameworks for 3-unit FDPs were made with 3 fabrication methods for a model with 2 abutment preparations. Internal fit was measured with the replica method. A white silicone indicator material simulated the cement space. This was measured by light microscopy at ×20 magnification and a digital measurement program. Marginal fit was evaluated with the direct-sight technique at ×4.6 magnification and given a score from 1 to 5. One-way ANOVA and Tukey honest significance tests were used to evaluate differences among groups with regard to internal fit. The Kruskal-Wallis and Mann-Whitney U tests were used to calculate differences among groups with regard to marginal gap. The Pearson r test was used for correlations calculations (α=.05).
  
  
  RESULTS
  Statistically significant differences were found in both internal and marginal fit among the test groups (P<.003). The milled group had the best overall fit, followed by the cast and SLM groups.
  
  
  CONCLUSIONS
  SLM restorations had the poorest internal and marginal fit, whereas the milling method had the best results. The SLM technique did not achieve clinically acceptable values for internal fit.
authors.affiliation: Head, Dental Clinic, Department of Clinical Dentistry, The Faculty of Dentistry and Medicine, University of Bergen, Bergen, Norway.
authors.forename: Harald
authors.initials: H
authors.lastname: Nesse
authors.affiliation: Postgraduate student, Department of Clinical Dentistry, The Faculty of Dentistry and Medicine, University of Bergen, Bergen, Norway.
authors.forename: Dina Mari Åkervik
authors.initials: DM
authors.lastname: Ulstein
authors.affiliation: Postgraduate student, Department of Clinical Dentistry, The Faculty of Dentistry and Medicine, University of Bergen, Bergen, Norway.
authors.forename: Malene Myhre
authors.initials: MM
authors.lastname: Vaage
authors.affiliation: Associate Professor, Department of Clinical Dentistry, The Faculty of Dentistry and Medicine, University of Bergen, Bergen, Norway. Electronic address: marit.oilo@iko.uib.no.
authors.forename: Marit
authors.initials: M
authors.lastname: Øilo
mesh_terms: D002858:Chromium Alloys; D000044:Dental Abutments; D018772:Dental Marginal Adaptation; D003764:Dental Materials; D017266:Dental Prosthesis / Q000379:methods*; D006801:Humans; D008853:Microscopy
chemical_list: D002858:Chromium Alloys; D003764:Dental Materials