Abstract
Statement of problem
Although palladium-silver alloys have been marketed for over 3 decades for metal-ceramic
restorations, understanding of the corrosion behavior of current alloys is incomplete;
this understanding is critical for evaluating biocompatibility and clinical performance.
Purpose
The purpose of this in vitro study was to characterize the corrosion behavior of 3
representative Pd-Ag alloys in simulated body fluid and oral environments and to compare
them with a high-noble Au-Pd alloy. The study obtained values of important electrochemical
corrosion parameters, with clinical relevance, for the rational selection of casting
alloys.
Material and methods
The room temperature in vitro corrosion characteristics of the 3 Pd-Ag alloys and
the high-noble Au-Pd alloy were evaluated in 0.9% NaCl, 0.09% NaCl, and Fusayama solutions.
After simulated porcelain firing heat treatment, 5 specimens of each alloy were immersed
in the electrolytes for 24 hours. For each specimen, the open-circuit potential (OCP)
was first recorded, and linear polarization was then performed from –20 mV to +20
mV (versus OCP) at a rate of 0.125 mV/s. Cyclic polarization was subsequently performed
on 3 specimens of each alloy from –300 mV to +1000 mV and back to –300 mV (versus
OCP) at a scanning rate of 1 mV/s. The differences in OCP and corrosion resistance
parameters (zero-current potential and polarization resistance) among alloys and electrolyte
combinations were compared with the 2-factor ANOVA (maximum-likelihood method) with
post hoc Tukey adjustments (α=.05).
Results
The 24-hour OCPs and polarization resistance values of the 3 Pd-Ag alloys and the
Au-Pd alloy were not significantly different (P=.233 and P=.211, respectively) for the same electrolyte, but significant differences were found
for corrosion test results in different electrolytes (P<.001 and P=.032, respectively). No significant interaction was found between the factors of
alloy and electrolyte (P=.249 and P=.713, respectively). The 3 Pd-Ag silver alloys appeared to be resistant to chloride
ion corrosion, and passivation and de-alloying were identified for these alloys.
Conclusions
The Pd-Ag alloys test results showed excellent in vitro corrosion resistance and were
equivalent to those of the high-noble Au-Pd alloy in simulated body fluid and oral
environments. Passivation, de-alloying, and formation of a AgCl layer were identified
as possible corrosion mechanisms for Pd-Ag alloys.
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Article info
Publication history
Published online: September 28, 2017
Footnotes
Supported by National Institute of Dental and Craniofacial Research (grant DE10147).
This study was based on a portion of a dissertation submitted by D.S., in partial fulfillment of the PhD degree, Graduate School of The Ohio State University.
Identification
Copyright
© 2017 by the Editorial Council for The Journal of Prosthetic Dentistry.
