title: Effect of casting atmosphere on the marginal deficiency and misfit of Ni-Cr alloys with and without beryllium.
abstract: BACKGROUND
  The marginal adaptation of prosthetic crowns is still a significant clinical problem.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate the marginal deficiency and misfit of Ni-Cr alloys with and without beryllium under different casting conditions.
  
  
  METHODS
  Four casting conditions were selected: flame-torch, induction/argon, induction/vacuum, and induction/air; and 2 alloys were used, Ni-Cr-Be and Ni-Cr. For each group, 10 metal specimens were prepared. Silicone indirect impressions and analysis of the degree of rounding were used to evaluate the marginal deficiencies of metal copings, and a standardized device for the setting pressure associated with optical microscopy was used to analyze the marginal misfit. Results were evaluated with 2-way ANOVA (α=.05), followed by the Tukey honest significant difference post hoc test, and the Pearson correlation test (α=.05).
  
  
  RESULTS
  Alloy (P<.001) and casting technique (P<.001) were shown to affect marginal deficiencies. The Ni-Cr cast using the torch technique showed the highest marginal deficiency, and the Ni-Cr-Be cast in a controlled argon atmosphere showed the lowest (P<.001). Alloy (P=.472) and casting techniques (P=.206) did not affect the marginal misfit, but significant differences were found in the interaction (P=.001); the lowest misfit was achieved using the Ni-Cr-Be, and the highest misfit occurred with the molten Ni-Cr, using the cast torch technique. No correlation was found between deficiency and marginal misfit (r=.04, P=.69).
  
  
  CONCLUSIONS
  The interactions demonstrated that the alloy containing beryllium that was cast in an argon atmosphere led to reduced marginal deficiency. Improved marginal adaptation can be achieved for the same alloy by using the torch technique.
authors.affiliation: Private practice, Santa Rosa do Viterbo, Brazil.
authors.forename: Leandro J
authors.initials: LJ
authors.lastname: da Silva
authors.affiliation: Associated Professor, Department of Dentistry of the Federal University of Sergipe, Sergipe, Brazil.
authors.forename: Monica B
authors.initials: MB
authors.lastname: Leal
authors.affiliation: Doctoral student, Department of Dental Materials and Prosthodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: Mariana L C
authors.initials: MLC
authors.lastname: Valente
authors.affiliation: Doctoral student, Department of Dental Materials and Prosthodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: Denise T
authors.initials: DT
authors.lastname: de Castro
authors.affiliation: Associate Professor, Department of Dental Materials and Prosthodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: Valéria O
authors.initials: VO
authors.lastname: Pagnano
authors.affiliation: Associate Professor, Department of Dental Materials and Prosthodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, Brazil. Electronic address: andreare@forp.usp.br.
authors.forename: Andréa C
authors.initials: AC
authors.lastname: Dos Reis
authors.affiliation: Professor, Department of Dental Materials and Prosthodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: Osvaldo L
authors.initials: OL
authors.lastname: Bezzon
mesh_terms: D001128:Argon; D001272:Atmosphere; D001608:Beryllium / Q000737:chemistry*; D002858:Chromium Alloys / Q000737:chemistry*; D003442:Crowns; D003734:Dental Casting Investment / Q000737:chemistry*; D003735:Dental Casting Technique / Q000295:instrumentation; D003760:Dental Impression Materials; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry; D017267:Dental Prosthesis Design; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D008853:Microscopy; D009532:Nickel; D011312:Pressure; D012826:Silicone Elastomers / Q000737:chemistry; D013499:Surface Properties; D014618:Vacuum
chemical_list: D002858:Chromium Alloys; D003734:Dental Casting Investment; D003760:Dental Impression Materials; D003764:Dental Materials; D016876:Metal Ceramic Alloys; D012826:Silicone Elastomers; C403005:nickel-chromium-beryllium alloy; D001128:Argon; D009532:Nickel; D001608:Beryllium