title: Evaluation of the marginal and internal gap of metal-ceramic crown fabricated with a selective laser sintering technology: two- and three-dimensional replica techniques.
abstract: OBJECTIVE
  One of the most important factors in evaluating the quality of fixed dental prostheses (FDPs) is their gap. The purpose of this study was to compare the marginal and internal gap of two different metal-ceramic crowns, casting and selective laser sintering (SLS), before and after porcelain firing. Furthermore, this study evaluated whether metal-ceramic crowns made using the SLS have the same clinical acceptability as crowns made by the traditional casting.
  
  
  METHODS
  The 10 study models were produced using stone. The 20 specimens were produced using the casting and the SLS methods; 10 samples were made in each group. After the core gap measurements, 10 metal-ceramic crowns in each group were finished using the conventional technique of firing porcelain. The gap of the metal-ceramic crowns was measured. The marginal and internal gaps were measured by two-dimensional and three-dimensional replica techniques, respectively. The Wilcoxon signed-rank test, the Wilcoxon rank-sum test and nonparametric ANCOVA were used for statistical analysis (α=.05).
  
  
  RESULTS
  In both groups, the gap increased after completion of the metal-ceramic crown compared to the core. In all measured areas, the gap of the metal cores and metal-ceramic crowns produced by the SLS was greater than that of the metal cores and metal-ceramic crowns produced using the casting. Statistically significant differences were found between cast and SLS (metal cores and metal-ceramic crown).
  
  
  CONCLUSIONS
  Although the gap of the FDPs produced by the SLS was greater than that of the FDPs produced by the conventional casting in all measured areas, none exceeded the clinically acceptable range.
authors.affiliation: Department of Dental Laboratory Science and Engineering, Korea University, Seoul, Republic of Korea.
authors.forename: Ki-Baek
authors.initials: KB
authors.lastname: Kim
authors.forename: Jae-Hong
authors.initials: JH
authors.lastname: Kim
authors.forename: Woong-Chul
authors.initials: WC
authors.lastname: Kim
authors.forename: Hae-Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Ji-Hwan
authors.initials: JH
authors.lastname: Kim
keywords: CAD-CAM; Marginal adaptation; Metal ceramics restorations; Replica techniques