title: Effect of soldering on the metal-ceramic bond strength of an Ni-Cr base alloy.
abstract: BACKGROUND
  Although soldering is a common laboratory procedure, the use of soldering alloys may adversely affect metal-ceramic bond strength and potentially decrease the longevity of metal-ceramic restorations.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the effect of soldering on metal-ceramic bond strength of a representative Ni-Cr base metal alloy.
  
  
  METHODS
  Twenty-eight rectangular (25 x 3 x 0.5 mm) Ni-based alloy (Wiron 99) specimens were equally divided into soldering (S) and reference (R) groups. Soldering group specimens were covered with a 0.1-mm layer of the appropriate solder (Wiron-Lot) and reduced by 0.1 mm on the opposite side. Five specimens of each group were used for the measurement of surface roughness parameter (R(z)) and hardness, and 3 were used for measurement of the modulus of elasticity. Six specimens of each group were covered with porcelain (Ceramco 3) and subjected to a 3-point bending test for evaluation of the metal-ceramic bond strength according to the ISO 9693 specification. The data from surface roughness, hardness, modulus of elasticity, and metal-ceramic bond strength were analyzed statistically, using independent t tests (alpha=.05).
  
  
  RESULTS
  Statistical analysis of the R(z) surface roughness parameter (S: 3.4 +/- 0.3 mum; R: 3.7 +/- 0.7 microm; P=.07) and bond strength (S: 46 +/- 3 MPa; R: 40 +/- 5 MPa; P=.057) failed to reveal any significant difference between the 2 groups. The specimens of the soldering group demonstrated significantly lower values both in hardness (S: 128 +/- 11 VHN; R: 217 +/- 4 VHN; P<.001) and in modulus of elasticity (S: 135 +/- 4 GPa; R: 183 +/- 6 GPa; P=.035) than the reference group.
  
  
  CONCLUSIONS
  Under the conditions of the present study, the addition of solder to the base metal alloy did not affect the metal-ceramic bond strength.
authors.affiliation: Department of Prosthodontics, School of Dentistry, University of Athens, Greece.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Nikellis
authors.forename: Anna
authors.initials: A
authors.lastname: Levi
authors.forename: Spiros
authors.initials: S
authors.lastname: Zinelis
mesh_terms: D002858:Chromium Alloys; D001840:Dental Bonding; D012994:Dental Soldering; D003799:Dental Stress Analysis; D004548:Elasticity; D006244:Hardness; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D009532:Nickel; D018583:Pliability; D013499:Surface Properties
chemical_list: D002858:Chromium Alloys; D016876:Metal Ceramic Alloys; D009532:Nickel