Influence of a Nanoporous Zirconia Implant Surface of on Cell Viability of Human Osteoblasts

Purpose: The dense nonretentive surface of zirconia implants was modified into a nanoporous surface using selective infiltration etching surface treatment. The aim of this study was to investigate the influence of such a nanoporous modified zirconia surface on the attachment of human osteoblasts. Materials and Methods: Human osteoblasts were cultured for 21 days on (i) selective infiltration etched zirconia (nanoporous surface), (ii) polished zirconia, (iii) polished titanium, or (iv) airborne particle abraded acid etched (SLA) titanium disks. After the culture period the following parameters were assessed: number of cells, the morphology of the cells, the attachment of the cells, alkaline phosphatase activity, and the level of total protein (= 0.05). Results: Statistical analysis revealed a significantly higher cell count on the third (F = 17.4, p < 0.001) and eighth day (F = 163, p < 0.001) for nanoporous zirconia and SLA titanium surfaces compared to polished specimens. The number of cells (nanoporous zirconia 160 +/- 20/mm2, SLA titanium 133 +/- 15/mm2) and cell size (nanoporous zirconia 50.7 +/- 3 m, SLA titanium 42.5 +/- 4 m) were significantly higher than polished specimens. Nanoporous zirconia specimens demonstrated comparable alkaline phosphatase activity (0.0036 +/- 0.0035 ng/l) and intracellular protein content (72.7 +/- 0.9 ng/l) compared to other tested groups. Scanning electron microscopy revealed that cells attached on the polished surface using finger-like processes, whereas on the nanoporous surface, finger-like processes were not observed, as the cell membrane appeared to be in close proximity to the underlying surface. Conclusion: The findings of this study suggest that a nanoporous zirconia surface favors cell growth and attachment compared to a polished surface. It was proposed that a nanoporous zirconia surface may improve clinical performance of zirconia implants.