Evaluation of biocompatibility of various ceramic powders with human fibroblasts in vitro

Cell reaction to powders of ceramics was studied in vitro. Cultured human fibroblasts were exposed to different types of ceramic powders: zirconia (ZP), alumina (A), tricalcium phosphate (TCP) and hydroxyapatite (HA), at various concentrations. The cell viability at the different exposure times was measured by the colony formation (expressed as colony forming efficiency, CFE), neutral red uptake (NR) and colorimetric tetrazolium (MTT) reduction. Alumina and hydroxyapatite showed no cytotoxic effects at studied doses (1-500 mug/ml) while zirconia and tricalcium phosphate inhibited cell viability, with 50% of CFE reduction at the concentration of about 50 mug/ml. In order to study the cytotoxic mechanism of zirconia powder, two further experiments were included, viz. the cellular response to the sintered zirconia ceramic powders (CZP) which were obtained by crushing the sintered ceramic material; and the measurement of the degradation of zirconia ceramic plate in the different solutions, i.e., either in saline or in 0.02 M lactic acid (pH 2.72). Similar cell reactions were obtained for the CZP and ZP by using MTT and NR assays. Slow releases of ions from zirconia ceramic plate, yttrium in both solutions and zirconium and yttrium in lactic acid, were detected.