Effect of metallographic structure and machining process on the apatite-forming ability of sodium hydroxide- and heat-treated titanium

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.

(Retracted) Image restoration and quantitative metallographic tissue based on machine vision

“…The improved Mahalanobis distance can eliminate the influence of noise to a certain extent, making the clustering results of noisy image blocks more accurate. (2) The calculation method of gray entropy further considers the gray uniformity in the target and background area of the metallographic image. (3) It avoids the binarization of the metallographic image caused by a single algorithm due to different image gray levels.…”

“…However, the research process has not been made public. Miyazaki et al 2 undertook various preheating and machining processes on Ti substrates, followed by NaOH and heat treatment. However, this study is largely impractical.…”

Compositional dependence of the apatite formation ability of Ti–Zr alloys designed for hard tissue reconstruction

“…Rate of corrosion corresponding to surface oxide formation was evaluated by polarization test. It was performed in 1 M NaOH aqueous solution using a potentiostat (HA-151A, Hokuto Denko Co., Tokyo, Japan) equipped with a saturated calomel electrode as the reference electrode and a Pt electrode as the counter electrode [17]. The specimens were embedded in acrylic resin and the cross-section was abraded with #120, #240, and #500 SiC paper.…”