The effect of recasting on corrosion of a silver-palladium alloy.
OBJECTIVE
Noble and semi-noble dental casting alloys are often reused by recasting. The aim of this study was to determine if repeated casting has a detrimental effect on the corrosion behavior of a silver-based dental alloy.


METHODS
A commercial Ag-Pd-Cu-Au alloy was cast and four times recast. Electrochemical tests were performed to determine the effects of recasting on the polarization parameters and the corrosion current density in artificial saliva. Changes in hardness, chemical composition and microstructure were determined.


RESULTS
Recasting had little effect on the shape of the polarization curves, but the corrosion current density dramatically increased after the fifth cast. Hardness increased with recasting and the microstructure showed grain growth. Increased subgrain formation was found for the fifth cast. The elemental map showed decreased surface concentration of Au for the fifth cast. The bulk concentrations of Au, Ag and Pd remained constant, but the copper and zinc contents slightly decreased and the content of impurities increased.


CONCLUSIONS
Recasting of an Ag-Pd-Cu-Au alloy initially had little effect on the corrosion susceptibility in artificial saliva, but a severe degradation of properties was observed after the fifth cast. The results indicate that a dental alloy of this type can be safely recast only a small number of times.
Horasawa
Noriko
N
Department of Dental Technology, School of Dentistry, Matsumoto Dental University, 1780 Hiro-oka Gobara, Shiojiri, Nagano Pref 399-0781, Japan. horasawa@po.mdu.ac.jp
Marek
Miroslave
M
D000704:Analysis of Variance; D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry*; D003735:Dental Casting Technique; D004563:Electrochemistry; D004577:Electron Probe Microanalysis; D017743:Equipment Reuse; D012464:Saliva, Artificial
C120982:Ag-Pd-Cu-Au alloy; D003722:Dental Alloys; D012464:Saliva, Artificial