Characterization of the interface of two dental palladium alloys cast on a prefabricated implant gold cylinder

The interface between two dental alloys (Pd-Cu-Ga, Pd-Ga) cast-to a prefabricated gold cylinder in two thicknesses (1, 2 mm) was investigated. Specimens were observed in optical and scanning electron microscopes. Line scan microanalysis by EDS was performed and polarization curves were taken. Gold cylinders shape was preserved. Characteristic elongated grains were detected at the gold cylinder alloy. The boundaries between the cylinder and the cast-to alloys were distinct. The 2 mm thick Pd-Ga alloy cast to the gold cylinder revealed high porosity at the interface, while the rest of the subgroups showed no or negligible porosity. Line scan analysis revealed the gradual diffusion of the main elements of each alloy in the structure of the gold cylinder and vice-versa in a 3-5 μm zone. Corrosion behaviour was estimated by cyclic polarization tests in 1 M lactic acid. The polarization curves showed negative hysteresis. In the reverse anodic scan the current density was less than that for the forward scan. This fact confirms that all the tested materials are not susceptible to corrosion in 1 M lactic acid.