title: Evaluation of Bond Strength of Pressed and Layered Veneering Ceramics to Nickel-Chromium Alloy.
abstract: BACKGROUND
  The success of metal- ceramic- restorations (MCR) depends on the presence of strong bond between porcelain and metal substructure.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the effect of hot pressing technique on the bond strength of a metal-porcelain composite in comparison to layering technique.
  
  
  METHODS
  Thirty Nickel-Chromium specimens were produced by two methods; conventional porcelain layering on metal and hot pressing (n=15). Bond strengths of all specimens were assessed by the means of three-point bending test according to ISO 9693: 1999 (E) instructions. The data were analyzed using Students t-test (p< 0.001).
  
  
  RESULTS
  The mean ± SD bond strength of conventional and hot pressing technique was 48.29 ± 6.02 and 56.52 ± 4.97, respectively. Therefore, the conventional layering technique yielded significantly lower mean bond strength values than hot pressing technique (p< 0.001).
  
  
  CONCLUSIONS
  This study showed that it is possible to improve metal-porcelain bond strength significantly by applying an overpressure during porcelain firing.
authors.affiliation: Dept. of Prosthodontic, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Mitra
authors.initials: M
authors.lastname: Farzin
authors.affiliation: Biomaterial Research Center, Dept. of Prosthodontic, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Amir Alireza
authors.initials: AA
authors.lastname: Khaledi
authors.affiliation: Postgraduate Student, Dept. of Orthodontic, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Behnam
authors.initials: B
authors.lastname: Malekpour
authors.affiliation: Dental Student, Student Research Committee, Dept. of Prosthodontic, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Mohammad Hassan
authors.initials: MH
authors.lastname: Naseri
keywords: Bond; Layering porcelain; Metal; Pressable porcelain