title: Evaluation of marginal and internal fit of ceramic and metallic crown copings using x-ray microtomography (micro-CT) technology.
abstract: BACKGROUND
  Prosthetic crown fit to the walls of the tooth preparation may vary depending on the material used for crown fabrication.
  
  
  OBJECTIVE
  The purpose of this study was to compare the marginal and internal fit of crown copings fabricated from 3 different materials.
  
  
  METHODS
  The selected materials were zirconia (ZirkonZahn system, group Y-TZP), lithium disilicate (IPS e.max Press system, group LSZ), and nickel-chromium alloy (lost-wax casting, group NiCr). Five specimens of each material were seated on standard dies. An x-ray microtomography (micro-CT) device was used to obtain volumetric reconstructions of each specimen. Points for fit measurement were located in Adobe Photoshop, and measurements were obtained in the CTAn SkyScan software environment. Marginal fit was measured at 4 points and internal fit at 9 points in each coping. Mean measurements from the 3 groups were compared by analysis of variance (ANOVA) at the 5% significance level, and between-group differences were assessed with the Tukey range test.
  
  
  RESULTS
  The nickel-chromium alloy exhibited the best marginal fit overall, comparable with zirconia and significantly different from lithium disilicate. Lithium disilicate exhibited the lowest mean values for internal fit, similar to zirconia and significantly different from the nickel-chrome alloy.
  
  
  CONCLUSIONS
  The marginal and internal fit parameters of the 3 tested materials were within clinically acceptable range.
authors.affiliation: Professor, Department of Prosthodontics, Federal University of Santa Maria, Santa Maria, Brazil.
authors.forename: Manuel Antonio
authors.initials: MA
authors.lastname: Pimenta
authors.affiliation: Professor, Department of Prosthodontics, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Luis Carlos
authors.initials: LC
authors.lastname: Frasca
authors.affiliation: Professor, Department of Nuclear Engineering, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Lopes
authors.affiliation: Professor, Postgraduate Program in Dentistry, Lutheran University of Brazil, Canoas, Brazil. Electronic address: elkenrivaldo@gmail.com.
authors.forename: Elken
authors.initials: E
authors.lastname: Rivaldo
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D002858:Chromium Alloys / Q000737:chemistry*; D003442:Crowns; D045662:Dental Etching / Q000379:methods; D018772:Dental Marginal Adaptation / Q000592:standards*; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008422:Materials Testing; D013499:Surface Properties; D055114:X-Ray Microtomography / Q000379:methods*; D015019:Yttrium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D002858:Chromium Alloys; D003764:Dental Materials; C508050:IPS e.max Press; C493120:lithia disilicate; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium; D000537:Aluminum Oxide