Characterization of thin hydroxyapatite layers formed on anodic titanium oxide films containing Ca and P by hydrothermal treatment

Abstract

An anodic titanium oxide film containing Ca and P (AOFCP) was formed on commercially pure titanium which was anodized in an electrolytic solution of dissolved beta-glycerophosphate (beta-GP) and calcium acetate (CA). Hydroxyapatite (HA) crystals were precipitated by hydrothermally heating the AOFCP at 300 degrees C. After hydrothermal treatment, the film was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray microanalysis (EDX), and tensile tests. The morphology, composition, and amount of HA crystals precipitated were significantly affected by the composition of the electrolytes. Near-stoichiometric HA crystals with high crystallinity were precipitated completely covering the AOFCP surface at specific electrolyte concentrations. The HA layers were thin at 1-2 microns in thickness. The adhesive strength of the film increased with decreasing electrolyte concentration and the maximum value was about 40 MPa. In vitro tests for 300 days suggested that the stability of the film was high. The high adhesive strength may result from the AOFCP existing as an intermediate layer between the HA layer and a titanium substrate. The intervention of the AOFCP may have prevented abrupt changes in Ca and P content at an HA coating-titanium interface as seen in a plasma-sprayed one. The porous TiO2 matrix of the AOFCP may be suitable for nucleation sites of HA crystals, as well as SiO2 matrix of silicate bioactive glasses or glass ceramics.

Bioactive Microarc Oxidized TiO2-based Coatings for Biomedical Implication

“…HA crystals were precipitated by hydrothermally treating the MAO coating at 300°C. The morphology, composition, and amount of HA crystals were significantly dependent on the electrolytes composition (Ishizawa et al, 1995). In the previous research , surface modification of titanium implant is processed by microarc oxidation and hydrothermal treatment.…”

“…And the apatite-forming ability of the MAO coatings is not very good. Thus, the subsequent modifications have been developed such as sol-gel, ultraviolet (UV) irradiation and hydrothermal treatment (Li et al, 2005;Han et al, 2008;Ishizawa et al, 1995). Authors have developed a simple method of chemical-treatment to modify the surfaces of the MAO coatings for improving the inducation ability for the formation of biomimetic apatite Wei et al, 2008).…”

Surface Modification Techniques for Biomedical Grade of Titanium Alloys: Oxidation, Carburization and Ion Implantation Processes

“…Anodic oxidation can be used for producing different types of protective oxide layer on different metals. (Ishizawa and Ogino, 1995). They further proceeded exploring and able to transform it into hydroxyapatite by applying hydrothermal treatment.…”

“…Due to superior corrosion resistance, thermal stability, photocatalytic activity, wear resistance and CO sensing properties makes MAO coatings as a popular research area (Shin et al, 2006, Jin et al, 2008. MAO has been popular in the biomedical community since Ishizawa et al pioneered the technique to biomedical titanium implants (Ishizawa and Ogino, 1995). Biomimetic deposition of apatite is possible on Ca and P-containing MAO coatings (Song et al, 2004).…”

Enhanced Performance of Osteoblasts by Silicon Incorporated Porous TiO2 Coating

“…To improve the osseointegration ability of Ti and its alloys, various techniques including sand-blasting, acid-etching, coating with bioactive materials, or micro-arc oxidation (MAO) were developed over the last decades [4][5][6][7] . Among these techniques, MAO treatment of Ti has attracted a great deal of attention because MAO can produce a porous, relatively rough, and firmly adherent titanium oxide (TiO 2 ) film on Ti plate and coat implants with complex three-dimensional geometries [8][9][10] .…”