title: Influence of porcelain firing and cementation on the marginal adaptation of metal-ceramic restorations prepared by different methods.
abstract: BACKGROUND
  Marginal adaptation plays an important role in the survival of metal-ceramic restorations. Porcelain firings and cementation may affect the adaptation of restorations. Moreover, conventional casting procedures and casting imperfections may cause deteriorations in the marginal adaptation of metal-ceramic restorations.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to compare the marginal adaptation after fabrication of the framework, porcelain application, and cementation of metal-ceramic restorations prepared by using the conventional lost-wax technique, milling, direct metal laser sintering (DMLS), and LaserCUSING, a direct process powder-bed system. Alterations in the marginal adaptation of the metal frameworks during the fabrication stages and the precision of fabrication methods were evaluated.
  
  
  METHODS
  Forty-eight metal dies simulating prepared premolar and molar abutment teeth were fabricated to investigate marginal adaptation. They were divided into 4 groups (n=12) according to the fabrication method used (group C serving as the control group: lost-wax method; group M: milling method; group LS: DMLS method; group DP: direct process powder-bed method). Sixty marginal discrepancy measurements were recorded separately on each abutment tooth after fabrication of the framework, porcelain application, and cementation by using a stereomicroscope. Thereafter, each group was divided into 3 subgroups according to the measurements recorded in each fabrication stage: subgroup F (framework), subgroup P (porcelain application), and subgroup C (cementation). Data were statistically analyzed with univariate analysis of variance (followed by 1-way ANOVA and Tamhane T2 test (α=.05).
  
  
  RESULTS
  The lowest marginal discrepancy values were observed in restorations prepared by using the direct process powder-bed method, and this was significantly different (P<.001) from the other methods. The highest marginal discrepancy values were recorded after the cementation procedure in all groups.
  
  
  CONCLUSIONS
  The results showed that the direct process powder-bed method is quite successful in terms of marginal adaptation. The marginal discrepancy increased after porcelain application and cementation.
authors.affiliation: Researcher, Department of Prosthodontics, Faculty of Dentistry, University of Ondokuz Mayis, Samsun, Turkey. Electronic address: necati_kaleli@hotmail.com.
authors.forename: Necati
authors.initials: N
authors.lastname: Kaleli
authors.affiliation: Chief and Professor, Department of Prosthodontics, Faculty of Dentistry, University of Ondokuz Mayis, Samsun, Turkey.
authors.forename: Duygu
authors.initials: D
authors.lastname: Saraç
mesh_terms: D002484:Cementation / Q000379:methods*; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D016876:Metal Ceramic Alloys
chemical_list: D016876:Metal Ceramic Alloys; D003776:Dental Porcelain