Several techniques have been described to modify the surface of titanium to make it more bioactive. Heat treatment (HT) and sodium hydroxide treatment (NaOH) have been used and can change the crystallinity and surface chemistry of titanium implants. However, no studies have systemically focused on comparing these different methods and their effect on the bioactivity of Ti. Therefore, in this study, Ti substrates were systematically treated using HT, NaOH, and a combination of HT and NaOH. The Ti plates were heat treated at various temperatures, and the plates were subjected to HT followed by soaking in NaOH or first soaked in NaOH and then heat treated. The morphology, crystallinity, hardness, water contact angle, and surface energy of the samples were analyzed as well as the bioactivity after immersion in PBS. Morphology and crystallinity changed with increasing temperature. The difference was most pronounced for the 800°C treated samples. The water contact angle decreased, and the surface energy increased with increasing temperature and was highest for 800°C. The rutile surface showed faster hydroxyapatite formation. NaOH treatment of the HT Ti samples increased the surface energy and improved its bioactivity further. Also, HT of NaOH samples improved the bioactivity compared to only HT. 1. Introduction Titanium has become a well-established material in orthopedic and dental applications because of its biocompatibility, strength, and corrosion resistance [1–3]. One of the key reasons for Ti’s ability to be tolerated and integrated into bone tissue is its surface properties, which is mainly correlated to the thin titanium oxide surface layer that forms spontaneously in air [4]. But there is room for continued improvement of Ti’s stability in host tissue, for example, via surface treatments to enhance the positive effect of the surface oxide. Several techniques have been used to modify the surface of titanium to increase its bone integration or even produce a bioactive surface (to promote bone bonding) [5–8]. Examples of such methods include acid etching of the Ti surface to enhance the surface roughness and coating the titanium substrate with a hydroxyapatite to form a surface that is similar to bone tissue [6, 7, 9]. One coating technique used for both bioactivity testing and HA coating method is the biomimetic process developed by Uchida et al. [8]. Bioactivity of a material is defined as the ability to form a chemical bond to bone in vivo [10]. In Kokubo’s method, an implant material is soaked in a simulated body fluid (SBF) at 37°C for up to four
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