Effect of ZrO2 content on ageing resistance and osteogenic cell differentiation of ZrO2-Al2O3 composite

Abstract

Two commercial 3 mol% yttria-partially stabilized zirconia powders, with 0.3 wt% Al2O3 (YZA) and without Al2O3 (YZ), were used to produce alumina (Al2O3)-zirconia (ZrO2) slip cast composites. The influence of the ZrO2 content and the ZrO2 grain size on the ageing behavior of the different Al2O3-ZrO2 composites was investigated. In addition, the in vitro biocompatibility and osteogenic cell differentiation of Al2O3-ZrO2 surfaces were evaluated before ageing (ba) and after ageing (aa) using the rat bone marrow-derived osteoblast cell culture model; the osteogenic potential of preosteoblast MC3T3-E1 cells on the same surfaces was also assessed. The ageing susceptibility of the composites significantly increased with increasing the ZrO2 content over 22 vol%. For ZrO2 contents ≤22 vol%, the grain size did not influence the transformability of tetragonal ZrO2 under ageing conditions; however, in the composites with 50 vol%, the greater grain size of 50 vol% YZ with respect to 50 vol% YZA enhanced the ageing degradation. Overall, the cell culture experiments revealed no significant differences among the composites before ageing in terms of osteogenic cell differentiation, except for the higher mineralization of bone marrow-derived osteoblast cells grown on 50 vol% YZ ba compared with the ones grown on 50 vol% YZA ba. The ageing process tended to rescue the osteogenic potential of these cells grown on 50 vol% YZA while inhibiting the one on 50 vol% YZ. In conclusion, the low ageing sensitive of the composites with ZrO2 contents ≤22 vol% did not change the osteoblast biocompatibility, whereas the greater ageing degradation of the composites with 50 vol% ZrO2 seemed to alter the osteogenic potential of bone marrow-derived osteoblast cells.