Wollastonite spin coating on zirconia substrate by sol-gel method

A wollastonite coating layer was fabricated on a zirconia substrate via a sol-gel method to improve the bioactivity of 3Y-TZPa bioinert material. Initially, the coated wollastonite surface possessed a porous microstructure; however, the coated area and film thickness increased proportionally with the increasing number of coating cycles. Furthermore, it was observed that dense and thin coating layers were formed on the zirconia substrate after one or two coating cycles; however, after three or four coating cycles, it was observed that porous and thick coating layers were formed on the zirconia substrate. The surface roughness depended on the thickness of the wollastonite coating layer, which increased with the increasing number of coating cycles. An in vitro test was conducted, wherein a wollastonite-coated specimen was immersed in a simulated body fluid solution for 14 days. The test results revealed that new hydroxyapatite particles precipitated and covered the surface of the wollastonite coating layer, thus confirming that the wollastonite coating layer significantly improved the bioactivity of zirconia, compared to the pure zirconia surface.