The effect of fluoride treatment on titanium treated with anodic spark oxidation

This study examined the effect of fluoride on the surface characteristics of an anodized titanium implant. Commercial pure titanium plate 20mm × 10mm × 2 mm in size, and discs 1.5 mm thick and 1.5 mm in diameter, were used. The prepared samples were polished with #200 to # 1,000 SiC papers and were then washed sequentially with distilled water, alcohol and acetone. Anodic oxidation was performed using a regulated DC power supply in an electrolyte containing a mixture of 0.015 M DL-α-glycerophosphate disodium salt hydrate (DL-α-GP) and 0.2 M calcium acetate hydrate (CA) with an electric current density of 30 mA/cm² and voltage ranging from 0 to 290 V. The specimens were divided into four groups and a fluoride treatment was carried out Group 1 was thermally treated in a 0.05 M TiF₃ solution at 90°C, Group 2 was electrochemically treated at 150 V in a 0.05 M TiF ₃ solution, Group 3 was electrochemically treated at 150 V in a 0.05 M NaF solution, and Group 4 was electrochemically treated at 150 V in a 0.05 M HF solution. A porous oxide layer containing pores 1-4 μm in size was observed on the surface treated with anodic oxidation. The diameter of the pores was higher in the protrusion areas than in the sunken areas. A significant amount of fluoride ions was released in the initial period, with small amounts being released continuously thereafter. The viability of MC3T3 cells was high when the fluoride ion concentration was 10 ppm, but decreased with further increases in the fluoride concentration. A six-week immersion test in simulated body fluid (SBF) showed dense HA crystals in the group immersed in 0.05 M TiF₃ at 90°C, which indicated good biocompatibility.