Influence of Heating Conditions for Formation of a Thin Apatite Film on Zirconia Using a Molecular Precursor Method

Abstract

The influence of heating conditions, heating temperature, and heating time on the formation of a thin carbonate-containing hydroxyapatite (CA) film onto partially stabilized zirconia using a molecular precursor method was evaluated. The molecular precursor solution was prepared from a mixture of calcium-ethylenediaminetetraacetic acid complex and phosphate compounds at Ca/P ratio of 1.67. After the application of molecular precursor solution onto zirconia, four different heating conditions—namely, 600 °C-2 h, 800 °C-2 h, 1000 °C-2 h, and 600 °C-4 h—were applied. No distinct difference of surface appearance of CA coating was observed between 600 and 800 °C-2 h. Fusion of apatite crystals was observed at 1000 °C-2 h. Surface roughness of CA film at 1000 °C-2 h was significantly higher than those under other heating conditions. Heating at 800 °C produced a significantly more hydrophilic surface and higher degree of crystallization. No significant differences were recognized in the critical load at the first crack in the coating among the four samples by scratch tests. After 30 days’ immersion in phosphate buffered saline, the four different CA coating films were still present. Simulated body fluid immersion experiments were performed as in vitro biocompatibility tests. After 48 h immersion, the CA film at 800 °C-2 h showed a greater amount of spherical crystal precipitation. It was suggested that properties of CA coating on partially stabilized zirconia using a molecular precursor method were influenced by the heating temperature and time.