NEW HIGH-PALLADIUM CASTING ALLOYS - STUDIES OF THE INTERFACE WITH PORCELAIN

This investigation studied the metal ceramic interface for two represe ntative high-palladium alloys each of the Pd-Cu-Ga and Pd-Ga systems, using scanning electron microscopy and x-ray energy dispersive spectro scopy. The Pd-Cu-Ga alloys produced complex subsurface oxidation regio ns with thicknesses ranging from 15 to 20 mu m for one alloy and 5 to 10 mu m for the other alloy. Ga, In, and Sn accumulated at the interfa ces, and Ga-rich deposits were found in the subsurface scale. One Pd-G a alloy presented a surface oxidation region which dissolved in the ce ramic, producing ''islands'' rich in Pd and Ca with a width that range d from 1 to 2 mu m. These islands were separated from the alloy by a b and rich in Ca and Si which was 1 to 2.5 mu m thick. While the other P d-Ga alloy presented similar interfacial microstructures, the ''island s'' formed for this alloy were relatively sparse. The Pd-Cu-Ca alloys had a more favorable interface for metal ceramic bonding, which agrees with previous characterization of bond failures between these alloys and dental porcelain.