[Corrosion behavior of Ag-Pd binary alloys under dynamic conditions and its cytotoxicity (in vitro)]

Ag-Pd binary alloys with various palladium contents were extracted in Eagle's minimum essential medium by dynamic extraction at 200 rpm at 37 degrees C. The extracts were filtered through a 0.22 microns cellulose acetate filter, and the silver and palladium amount of the extracts and filtrates as dissolved metallic elements was measured with atomic absorption spectroscopy. Extracts and filtrates were also used in cultivation of L-929 cells to study in vitro cytotoxicity. An increase in the palladium content of the alloy resulted in decreased silver dissolution and increased palladium dissolution. The amount of palladium in the filtrates increased as the extraction period was extended, but the amount of silver was negligible in all filtrates. Extracts which had been extracted for 1 day showed strong cytotoxicity in pure Ag. However, the addition of palladium at a weight percent of more than 40% decreased cytotoxicity almost to the control level. Filtrate which had been extracted for 1 or 3 days was noncytotoxic in all alloys. However, the filtrate which had been extracted for 5 or 7 days showed cytotoxicity, which was especially strong in high-palladium alloys. These results demonstrate that extraction using a dynamic method appears to be useful in the investigation of their corrosion and biocompatibility.