High-palladium alloys contain more than 75% Pd and are used for metal-ceramic restorations and implant-supported prostheses. The purpose of a series of investigations on these alloys included in this dissertation was to study the oxidation, porcelain adherence, and the mechanical properties and microstructures in the as-cast and heat-treated conditions, and the ability to fabricate dental restorations that maintain acceptable fit after casting and being subjected to simulated porcelain firings. An additional goal was to evaluate the porcelain adherence screening test. The high-palladium alloys selected for study were from both the Pd-Cu-Ga and Pd-Ga alloys of representative commercially available compositions.; Using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), it was observed that only Pd-Cu-Ga alloys produced complex subsurface oxidation regions (internal oxidation). Combined use of standard x-ray diffraction (XRD), angle-resolved XRD and x-ray photoelectron spectroscopy (XPS) revealed the mechanism of oxide formation and identified the oxide species formed.; Results from the porcelain adherence test were compared to the three-point bend test. Surprisingly, it was found that there was no correlation between the two static in vitro screening tests. It was concluded that the porcelain adherence may not be a good method for evaluation of the metal-ceramic bond.; The several Pd-Cu-Ga alloys evaluated exhibited similar mechanical properties; however, the single Pd-Ga alloy selected was softer and had higher percentage elongation. Heat treatment simulating the porcelain firing cycles eliminated the dendritic microstructure, decreased strength and increased ductility for three Pd-Cu-Ga alloys that had as-cast dendritic microstructures. Both the Pd-Cu-Ga and Pd-Ga studied alloys have the same modulus of elasticity. The amount of overall casting porosity was relatively minimal and not significantly different among the high-palladium alloys studied. Use of the tensile test revealed differences among the mechanical properties of the three alloys that were not observed previously by Vickers hardness testing.; Most of the selected high-palladium alloys had high-temperature distortion that was not significantly different in comparison to the control Au-Pd alloy. Most of this distortion occurred for the oxidation heating cycle. Apparently, high-temperature distortion should not be a problem for cast single crowns fabricated from high-palladium alloys.
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