Bioactivation of Yttria-Stabilized Tetragonal Zirconia Surface via a Chemical Treatment Processing Using a Calcium Phosphate Slurry

The present study demonstrates that the bioactivation of bioinert yttria-stabilized tetragonal zirconia (YSZ) substrates is achieved through a chemical treatment process using a calcium phosphate shiny. The slurry processing is simple: a YSZ, substrate was buried in a slurry agent prepared by mixing calcium phosphate powder and distilled water, and thereafter, the slurry including the substrate was heated in air. Treating by the processing, tiny hydroxyapatite (HAp) particles were deposited on the YSZ surface. The amount of the particles increased with an increase in the heating temperature up to 1223 K, while setting the temperature beyond 1373 K induced thermal decomposition into tricalciurn phosphate (TCP) and calcium oxide (CaO). When immersing in Hanks' balanced saline solution to evaluate bioactivation, HAp precipitation was only observed on the slurry-treated surface, and the mass thickness of the precipitation was enhanced with increasing heating temperatures up to 1223 K. Slurry-treated YSZ at 1223 K did not adversely affect the adhesion and proliferation of osteoblast-like cells. On the other hand, calcification of the cells was significantly promoted, indicating the activation of bone formation. In conclusion, slurry processing is a valuable technique that enhances the bioactivity of YSZ substrates with a simple one-step process.