Cytotoxicity of Metal Cations used in Dental Cast Alloys
Gottfried Schmalz, Dorthe Arenholt-Bindslev, Silke Pfüller and Helmut Schweikl
The toxicity of dental alloys depends upon the quantity and chemical state of metal elements released from the alloy into the affected tissue. The purpose of the present study was to investigate the effects of various cell lines, various cell numbers, and various serum concentrations on the cytotoxicity of metal cations which are components of dental alloys. Aqueous salt solutions were tested on two continuous cell lines (L-929 mouse fibroblast-like cells and HaK hamster epithelial-like kidney cells) and on primary human gingival fibroblasts. The cell culture medium was routinely supplemented with 5% fetal calf serum. The influence of the serum concentration on the cytotoxic potencies of metal cations was investigated by increasing the concentration to 20% in one series of experiments with L-929 cells. Cell reactions were recorded with the MTT test after exposure for 24 hours. The rank order of the cytotoxicity of cations in L-929 cells (10,000 cells/well, 5% serum) from the most to the least toxic was: Ag+, Zn2+, Cd2+, Hg2+, Au3+, Pt4+, Co2+, Cu2+, Ni2+, Pd2+, Mn2+, Nb5+, Mo5+, Ga3+, Cr3+, In3+, Sn2+. A variation in cell number between 5000 and 10,000 cells/well did not influence the results. Furthermore, no differences were observed in the cytotoxic responses of the two continuous cell lines. Variation in the serum content of L-929 cell culture medium had no significant influence on the cytotoxicity of most metal cations, except for Nb5+, Ni2+ and Sn2+. Primary human gingival fibroblasts showed the same rank order of toxicity as the continuous cell lines, but at higher concentrations of the test materials.