Cytotoxicity of Au-based dental solders alone and on a substrate alloy

Gold-based dental solders are commonly combined with a substrate alloy in dental prostheses and are in long-term intimate contact with oral tissues, yet the biological properties of dental solders are almost unknown. Previous studies have shown that combinations of dissimilar alloys may increase the risk of elemental release and adverse biological effects. The purpose of the current study was to measure the cytotoxicity of dental solders alone and in combination with a substrate metal. Based on previous reports, which measured the cytotoxicity of combinations of dissimilar alloys, we hypothesized that the cytotoxicity of solder-substrate combinations cannot be predicted based on the cytotoxicity of the solders alone. Specimens of 13 high-noble (Au >/= 40 wt%; Au+Pt+Pd >/= 60%) and 6 noble (Au+Pt+Pd >/= 25 wt%) solders were made either in bulk or in combination with a compatible Au-Pd substrate alloy. The results showed that, most often, solder-substrate combinations were less toxic than the solders alone, but three high-noble solders were more cytotoxic in combination. We concluded that, when screening new Au-based dental solders for cytotoxicity, the solder should be assessed in combination with a clinically relevant substrate alloy.