A ready made metal crown and a crown distal shoe have been widely used in clinical pedodontics. These alloys are composed of nickel, cobalt and chromium. We have studied the cytotoxity in vitro which bring about these metallic ions.
The cell line, which was derived from the human gingival fibroblast, has been used and these cells were grown in Eagle's MEM with 10% calf serum in a humidified atmosphere of air with 95% of CO₂ gas fusion at 37°C. The effect of these metalic ions was tested and the results were as follows: Ni: 12.5μg/ml-50.0μg/ml, Co: 6.25μg/ml-25.0μg/ml, Cr: 0.1μg/ml-1.0μg/ml. Fibroblasts were cultivated at a density of 8×10⁴ cells/ml in the culture media without metallic ions, and were incubated for 24 hours. Then, the culture media was replaced by a fresh media, containing either one of Ni, Co and Cr ions. The number of viable cells were calculated every 24 hours for the following six days, and the morphological changes of the cultivating cells were studied with a light microscope. This study showed that each metalic ion had induced similar morphological changes of the cells, and inhibited the cell growth rate. The concentrations of each metallic ion which inhibited cell growth were estimated between 12.5μg/ml and 25.0μg/ml for Ni, about 6.25μg/ml for Co, and between 0.1μg/ml and 0.5μg/ml for Cr. These results suggested that the level of cytotoxic effects were on the order of Cr, Co and Ni.