Evaluation of adhesion of hydroxyapatite films fabricated on biomedical Β-Type titanium alloy after immersion in ringer's solution

The adhesive strengths between sol-gel fabricated hydroxyapatite (HAp) films and Ti29Nb13Ta4.6Zr alloy (TNTZ) were evaluated before and after immersion in Ringer's solution at 310K for 7 d. The effect of the surface morphology of TNTZ on the adhesion of HAp films was also investigated. The fracture surfaces after adhesion tests were observed and fracture areas at the interface between HAp films and TNTZ were also evaluated before and after immersion in Ringer's solution. No significant differences in the adhesive strengths between HAp films and TNTZ disks with mirror-polished and mechanically polished surfaces were found. The fracture area at the interface between HAp film and mirror-polished TNTZ disk increases after immersion in Ringer's solution, whereas no fracture occurs at the interface between HAp film and mechanically polished TNTZ disk before and after immersion in Ringer's solution. It is supposed that Ringer's solution penetrates along the cracks that are formed in the HAp films during calcination and the regions with weak adhesion between HAp and TNTZ are connected during immersion in Ringer's solution in the case of HAp films fabricated on mirror-polished TNTZ. From these results, it is found that a relatively rougher surface is effective in improving the adhesion of HAp films fabricated on TNTZ before and after immersion in Ringer's solution.