Effects of anodizing conditions on surface features and bioactivities of titanium oxide nanotubes

Titanium has excellent biocompatibility with cells and tissues and is widely used for dental implants. Among the many methods for titanium surface modification, electrochemical techniques are simple and cheap. One example is anodic oxidation. Lower concentrations of ammonium fluoride in ethylene glycol electrolyte solution reduce costs and environmental impact. Titanium dioxide nanotubes (TNTs) were prepared by anodic oxidation under changing electrolytic conditions, such as different working voltages (10V to 40V) and working times (10 min to 40 min). The effects of surface morphology on the bioactivities of TNTs were assessed. From observations of SEM images, the working voltage was proportional to the diameter of TNTs. Moreover, working voltage/time significantly affected the surface morphology of TNTs. The surface morphology of TNTs under anodic oxidation at 30 V and 40 min was even and flat. TNT structure led to large increases in surface hydrophilicity. Further, anatase phase was achieved by annealing at 350°C for 2 hr. This significantly increased apatite deposition on TNT surface for better bioactivity.