Affiliations: [a] Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu, Japan | [b] Department of Applied Chemistry, Kyushu Institute of Technology, Kitakyushu, Japan | [c] Department of Materials Science and Engineering, Kyushu Institute of Technology, Kitakyushu, Japan | [d] Graduate School of Biomedical Engineering, Tohoku University, Sendai, Japan
Correspondence:
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Corresponding author: Toshiki Miyazaki, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, 2-4, Hibikino, Wakamatsu-ku, Kitakyushu 808-0196, Japan. Tel.: +81-93-695-6025; Fax: +81-93-695-6025; E-mail: tmiya@life.kyutech.ac.jp.
Abstract: Although titanium (Ti) is clinically used for hard tissue reconstruction, it has low bone-bonding ability, i.e. bioactivity. Materials able to deposit apatite on their surfaces within the body is considered to exhibit bioactivity. Effects of the metallographic structure and machining process of Ti on its apatite-forming ability remains unclear. In this study, Ti substrates subjected to various preheating and machining processes were then subjected to NaOH and heat treatments. The apatite-forming abilities of resulting Ti were examined in simulated body fluid (SBF). Preheating of the Ti decreased its reactivity with NaOH solution. When quenched or annealed Ti was subjected to NaOH and heat treatments, the induction period for apatite formation in SBF slightly increased. This was attributed to a decrease in sodium titanate and increase in rutile on the Ti surface after the treatments. Substrates subjected to wire-electrical-discharge machining did not form apatite. This was attributed to the inhibition of PO43− adsorption on their surfaces following Ca2+ adsorption, which is an essential process for apatite nucleation. Contamination of Ti surface by components of the brass wire used in the machining contributed to the inhibition. The bioactivity of surface-modified Ti was therefore significantly affected by its thermal treatment and machining process.
