title: The effect of repeated porcelain firings on corrosion resistance of different dental alloys.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effects of repeated porcelain firing process on the corrosion rates of the dental alloys.
  
  
  METHODS
  Cr-Co, Cr-Ni and Pd-Ag alloys were used for this study. Each metal supported porcelain consisted of 30 specimens of 10 for 7, 9 and 11 firing each. Disc-shaped specimens 10 mm diameter and 3 mm thickness were formed by melting alloys with a propane-oxygen flame and casted with a centrifuge casting machine and then with the porcelain veneer fired onto the metal alloys. Corrosion tests were performed in quintuplicate for each alloy (after repeated porcelain firing) in Fusayama artificial saliva solution (pH = 5) in a low thermal-expansion borosilicate glass cell. Tamhane and Sheffe test was used to compare corrosion differences in the results after repeated firings and among 7, 9 and 11 firing for each alloy. The probability level for statistical significance was set at α=0.05.
  
  
  RESULTS
  The corrosion resistance was higher (30 mV), in case of 7 times firing (Commercial). On the other hand, it was lower in case of 11 times firing (5 mV) (P<.05).
  
  
  CONCLUSIONS
  Repeated firings decreased corrosion resistance of Pd-Ag, Cr-Co and Cr-Ni alloys. The Pd-Ag alloy exhibited little corrosion in in vitro tests. The Cr-Ni alloy exhibited higher corrosion resistance than Cr-Co alloys in in vitro tests.
authors.affiliation: Department of Prosthetic Dentistry, Mustafa Kemal University, Hatay, Turkey.
authors.forename: Ali Riza
authors.initials: AR
authors.lastname: Tuncdemir
authors.forename: Ismail
authors.initials: I
authors.lastname: Karahan
authors.forename: Serdar
authors.initials: S
authors.lastname: Polat
authors.forename: Meral Arslan
authors.initials: MA
authors.lastname: Malkoc
authors.forename: Mehmet
authors.initials: M
authors.lastname: Dalkiz
keywords: Alloys; Corrosion test; Repeated firings