[In vitro study on biocompatibility of zirconium and titanium]

The purpose of this study is to evaluate the biocompatibility of zirconium compared with titanium by the in vitro study using human osteosarcoma cell line (HOS). Various characteristics of the HOS cells cultured on zirconium (99.9%) and titanium (99.9%) discs were investigated. On the colony formation of the HOS cells, there were no differences between the zirconium and titanium in colony size and number. Good proliferation of the HOS cells was observed on the zirconium as well as on the titanium. Morphological observation of the HOS cells by SEM revealed that the cells on the zirconium as well as on the titanium were flat and polygonal in shape with radial pseudopods. Collagen fibers and calcified substances were observed in the matrix of the HOS cells by TEM on the zirconium as well as on the titanium. The calcium of the HOS cell layer was stained well by Dahl's method. Analysis of the HOS cell layer by the Fourier transform infrared spectroscopy indicated that the HOS cells formed the same matrices including the apatite on the zirconium as on the titanium. Measurements of the zirconium and titanium elution into the human saliva indicated that the elution of zirconium was less than that of titanium. These results suggest that zirconium possesses as excellent biocompatibility as titanium.