Metallurgical structures, in vitro corrosion resistance and biocompatibility of high-palladium dental casting alloys

A transmission electron microscopic (TEM) investigation was performed on four representative commercial high-palladium dental alloys in both as-cast and simulated porcelain-firing heat-treated conditions. The results indicated that a tweed ultrastructure (space between striations ;In vitro corrosion resistance of five representative commercial high-palladium dental alloys in the as-cast and simulated porcelain-firing heat-treated conditions was evaluated by potentiostatic/potentiodynamic polarization, using two deaerated stagnant electrolytes: 0.09% NaCl and the Fusayama solutions. The deaerated Fusayama solution was considered to be a more corrosive environment, compared to the 0.09% NaCl solution, based on the results of this study. The Pd-Cu-Ga and Pd-Ga alloys showed similar electrochemical properties. The somewhat active electrochemical behavior for the two heat-treated Pd-Cu-Ga alloys, Liberty and Spartan Plus was attributed to casting defects and microstructural phases on the test specimen surface. The results from this in vitro study indicated that the high-palladium alloys in both the as-cast and heat-treated conditions show either an active-passive transition or retain passivity under electrochemical conditions similar to the oral environment. Heat-treated Freedom Plus had an unstable oxide film form on the surface during anodic polarization and appeared to have a tendency for crevice corrosion in the Fusayama solution.;With the widespread use of high-palladium alloys for metal-ceramic and all-metal restorations in many countries, many adverse effects related to these alloys have been publicized lately. This study provided a systematic summary of published information about the biocompatibility of palladium and some palladium compounds. The current literature on the biocompatibility of high-palladium dental alloys is discussed with particular attention to certain metallurgical and microstructural factors which may have important roles in vivo. Based on the currently available information, high-palladium dental alloys appear to be biocompatible materials, except for the hypersensitivity problem associated with these alloys in certain populations. Until a reliable method to test the hysensitivity of a subject to high-palladium alloys is developed, it is still the responsibility of a dentist to choose the appropriate dental alloy for his or her patient.