Performance of Bioactive Hydroxyapatite Coating after Soaking in Simulated Body Fluid

In this study, in vitro acellular bioactivity and tensile bonding strength of hydroxyapatite (HA) coating synthesized by sol-gel technique after long-term storage in simulated body fluid (SBF) for up to 32 days were studied. After soaking in SBF, it was observed that new bone-like apatite layer was formed on the coating indicating the bioactive nature. Bonding strength of sol-gel coated rods was found to decrease with soaking times, from 55 to 30 MPa. In comparison to adhesive bonded titanium rods which were used as control specimens, the values were found to be equal or even greater in certain soaking periods. Debonding at adhesive-titanium interface was the failure mode indicating that the coating is still intact. Therefore, it could be concluded that this sol-gel coating is bioactive and the coating adhesion to substrate is sufficiently strong.