In vitro reaction of macrophages to metal ions from dental biomaterials.

OBJECTIVE

This study was conducted to 1) measure the sensitivity of human and mouse macrophages to metal ions which are released from dental biomaterials, 2) compare these sensitivities with those of other cell types in the oral cavity, and 3) determine if metal ions alter the metabolism and synthetic processes of these cells at lower concentrations than are required to lyse the cells. This information will help define the biological risks associated with the release of metal ions into the oral cavity.

METHODS

Macrophages were exposed to a range of concentrations of Ag1+, Au3+, Cu2+, Hg2+, Ni2+, Pd2+, Pt4+, and Zn2+ for 24 h in cell culture. The concentrations which caused a 50% decrease in succinic dehydrogenase (SDH) activity, protein production, and lactate dehydrogenase (LDH) release were measured and compared with these values for fibroblasts and osteoblasts.

RESULTS

Most metal ions caused alteration in SDH activity and protein production at lower concentrations than were required to induce LDH release. There were exceptions to this trend, and the differences were not always statistically significant. Furthermore, although the macrophages sometimes had statistically different sensitivities to metal ions than fibroblasts or osteoblasts, these differences were less than one order of magnitude. Macrophage response to the metal ions was highly dependent on the metal ion and the species of macrophage.

CONCLUSIONS

Macrophages react adversely to metal ions at similar concentrations as other cell types found in the oral cavity. Furthermore, the concentrations which affect cell metabolism and protein production are generally lower than those which lyse the cells. Thus, non-lethal concentrations of metal ions may alter the secretion of protein inflammatory mediators such as cytokines which direct the inflammatory response in tissues.