| The apatite-forming ability of titanium oxide film with different structures has been investigated in a simulated body fluid (SBF). Titanium metals with different surface oxide structures were prepared. Firstly, a dense rutile film on tiianium was prepared with commercial titanium plates after is was heat-treated in air at 700℃ for half an. hour . Then, a layer of amorphous titania gel on the Ti surface was prepared with commercial pure titanium after it was treated with a solution consisting of 98%H2SO4, 34% HC1 and demonized water with 1:1:2 volume rate at 70℃ for half an hour, then treated with 6mol/L NaOH solution at 70℃ for five hours. Thirdly, a micro porous titanium oxide (rutile) film, which was coalesced by many small particles (the size about lOOnm) into large particles and pore (about l-5um), was prepared after the amorphous titania gel was heated in air at 700℃ for half an hour. The dense rutile and amorphous titania gel did not induce apatite formation on their surfaces in SBF solution in 48 hours, whereas the micro porous rutile structure induced apatite formation on their surfaces. This indicates that a nano porous structure of titania is also an effective factor to inducing apatite formation.The histological results showed that titanium metal covered by micro porousrutile prepared by two-step chemical and heat-treatment was the most bioactive material in bony tissue among the pure Ti, titanium covered by amorphous titania gel, and titanium covered by micro porous rutile.From the push-out testing results, an increased bone-bonding ability of titanium treated by the two-step chemical and heat-treatment, which was higher than that of pure Ti and comparable to that of two-step chemical treated Ti, was observed.Our results indicated that a spatially nano-scale porous structure of titanium oxide film was an important factor to facilitate the Ca-P nucleation. Both two-step chemical and heat-treated Ti are essential for bioactivity and bone-bonding ability in practical use.
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