RESPONSE OF L-929 FIBROBLASTS, HUMAN GINGIVAL FIBROBLASTS, AND HUMAN TISSUE MAST-CELLS TO VARIOUS METAL-CATIONS

Recent data suggest that under certain conditions, various metal catio ns are released from dental alloys. These ions may produce adverse eff ects in various cell types in vivo. In this study, the cytopathogenic effects of 13 metal cations on murine L-929 fibroblasts, human gingiva l fibroblasts, and human tissue mast cells were analyzed in vitro. Sev eral metal cations (dose range, from 0.0033 to 1.0 mmol/L) were found to induce dose-dependent inhibition of H-3-thymidine incorporation int o cultured fibroblasts. The rank order of potency (lowest observed eff ect level, LOEL) for L-929 fibroblasts was: Ag+ > Pt4+ > Co2+ > In3+ > Ga3+ > Au3+ > Cu2+ < Ni2+, Zn2+ > Pd2+ > Mo5+ > Sn2+ > Cr2+. A simila r rank order of potency was obtained for primary human gingival fibrob lasts: Pt4+ > Ag+ > Au3+, In3+ > Ga3+ > Ni2+ > Co2+ > Zn2+ > Cu2+ < Cr 2+, Pd2+ > Mo5+ > Sn2+. In primary human mast cells, Ag+ and Au3+ caus ed dose-dependent toxic histamine release, whereas the other metal cat ions were ineffective over the dose range tested. To investigate the m echanism of metal cation-induced effects, we performed DNA as well as electron microscopic analyses on cultured fibroblasts. Both the DNA pa ttern and the ultrastructure of L-929 cells and gingival fibroblasts a fter exposure to cytopathogenic metal cations revealed signs of necros is but no signs of apoptosis. Together, our data provide evidence that various metal cations produce dose-dependent cytopathogenic effects i n distinct cell types, including human gingival fibroblasts and human tissue mast cells. Further studies are required to assess whether thes e effects play a role in adverse reactions to dental alloys which rele ase metal cations in vivo.