Corrosion Characteristics of Palladium-Silver Dental Alloys Evaluated by Potentiodynamic Methods

Knowledge of the in vitro corrosion behavior of dental casting alloys is highly important as a first step towards understanding their biocompatibility. Purpose: Use potentiodynamic methods to evaluate in vitro corrosion characteristics of three palladium-silver alloys in simulated body fluid and oral environments. Methods: The following representative alloys were selected: Rx 91 (53.5Pd–37.5Ag–8.5Sn–In–Ru), Jeneric/Pentron; Super Star (59.8Pd–28.1Ag–6In–5Sn–Ga–Ru/Re) Heraeus Kulzer Jelenko; and W-1 (53.3Pd–37.7Ag–8.5Sn–In–Ru/Re, Ivoclar Vivadent. A high-noble gold-palladium alloy [Olympia (51.5Au-38.5Pd-8.5In-1.5Ga-Ru), Heraeus Kulzer Jelenko] was used as a control. Disk-shaped specimens of 1.25 cm diameter and 0.13 cm thickness were cast and oxidized. Simulated porcelain-firing heat treatment was then performed for all alloys. All specimens were ground and polished through 0.05 µm alumina slurries. Corrosion tests were performed in 0.09% and 0.9% NaCl solutions and Fusayama solution. The open circuit potential (OCP) after 24 hours immersion, linear polarization from –20 mV to 20 mV around the OCP, and cyclic polarization from –300 mV to 1000 mV and back to –300 mV (vs. OCP) were determined. Mean values of corrosion parameters for all four alloys in each electrolyte were compared by ANOVA, and the REGW multiple-range test was used to identify the specific comparisons yielding significant differences for the given parameter. Dunnett's method was used to simultaneously compare the differences for a given corrosion parameter between each of the three palladium-silver alloys and the control alloy Olympia. Results: The 24-hour OCP and polarization resistance of the tested palladium-silver alloys were equivalent to the high-noble gold-palladium alloy, and the palladium-silver alloys were resistant to chloride ion corrosion. Passivation and dealloying were identified during the anodic polarization of the palladium-silver alloys. Conclusion: Palladium-silver alloys have excellent corrosion resistance in simulated body fluid and oral environments. Supported by NIDCR Grant DE10147.