title: Corrosion of CoCr and NiCr dental alloys alloyed with palladium.
abstract: BACKGROUND
  A new subclass of casting alloy composition involving the addition of palladium (25 wt%) to traditional base metal alloys, thereby raising their classification to that of a noble alloy, has been recently introduced. Little is known about this class of casting alloy, particularly its corrosion properties, which influence its biocompatibility and esthetics.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the corrosion properties of 2 new CoPdCr and one new NiPdCr alloy and compare them to traditional CoCr and NiCr alloys.
  
  
  METHODS
  The casting alloys investigated were: CoPdCr-A (NobleCrown NF), CoPdCr-I (Callisto CP+), NiPdCr (Noble Crown), CoCr (Argeloy N.P. Special), and NiCr (Argeloy N.P. Star). Cylindrical (4.8-mm diameter) as-cast and oxidized specimens were assessed electrochemically in phosphate-buffered saline at 24°C (n=8 and n=6, respectively). The open circuit potential (OCP) was monitored for 20 hours, followed by linear polarization and cyclic polarization tests. A generalized linear mixed model was used to determine whether differences existed between alloys and to examine the effect of oxidation (α=.05). Representative alloy surfaces were scanned and examined with light microscopy.
  
  
  RESULTS
  The palladium-containing alloys possessed a significantly greater OCP (P<.001); however, their polarization resistance was less and the corrosion current density was significantly greater (P<.05) than their traditional CoCr and NiCr alloy counterparts. Additionally, a greater incidence of pitting was observed in the palladium-containing alloys. Some differences were noted within alloys between the as-cast and oxidized conditions, but a major trend was not observed.
  
  
  CONCLUSIONS
  Overall, the inclusion of palladium in CoCr and NiCr alloys had deleterious effects on electrochemical corrosion properties.
authors.affiliation: Department of General Dental Sciences, Marquette University School of Dentistry, Milwaukee, WI, USA.
authors.forename: Demetrios M
authors.initials: DM
authors.lastname: Sarantopoulos
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Beck
authors.forename: Robert
authors.initials: R
authors.lastname: Holsen
authors.forename: David W
authors.initials: DW
authors.lastname: Berzins
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D003343:Corrosion; D003734:Dental Casting Investment / Q000737:chemistry; D017097:Electric Impedance; D055664:Electrochemical Techniques; D006358:Hot Temperature; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors; D014618:Vacuum
chemical_list: C098420:A37 alloy; D001672:Biocompatible Materials; D002858:Chromium Alloys; D003734:Dental Casting Investment; D016876:Metal Ceramic Alloys; D003035:Cobalt; D010165:Palladium; D009532:Nickel