Cytotoxic effects of cobalt-chromium alloys on fibroblasts derived from human gingiva.

The in vitro toxicity of 15 different cobalt-chromium alloys used in removable partial dentures and dental implants was studied. The composition of the alloys was determined by X-ray spectrometry. Alloys were tested on human oral fibroblasts in low density, semiconfluent or confluent cultures. The cultures were observed in a phase contrast microscope over a period of 3 wk. The alloys could be divided into three groups depending upon the degree of cell injury evoked. Group I alloys caused no cell injury. Group II alloys caused slight to moderate cell injury seen first after 3-7 days of exposure. Group III alloys caused severe cell injury with signs of cell damage detected after 12 h and total cell death after 3-14 days. The alloys' composition varied considerably with regard to cobalt, chromium and nickel as well as other components. Nevertheless, group II and III alloys had a higher nickel content than group I alloys in general.