In vitro BIOACTIVITY OF TITANIA GEL LAYERS FORMED BY REACTION BETWEEN TITANIUM SUBSTRATE AND AN H₂O₂/TaC1₅ SOLUTION

Commercially pure titanium was treated with an H₂O₂/TaC1₅ solution. Thus formed titania gel layer remained amorphous when heated below 200°C and transformed to anatase after heated between 300-600°C. The anatase layers were substantially bioactive to deposit carbonate ion-incorporated apatite after soaked for 1 d in a simulated body fluid (Kokubo’s recipe), while the amorphous layers did not deposit up to 7 d. The apatite particles were preferably nucleated inside the cracks which prevailed in the titania gel layers. After soaking only for 2 d, the specimens were almost completely covered by the apatite. The H₂O₂-treated Ti specimens deposited apatite on both the contact and open surfaces, whereas the NaOH treated Ti specimens only deposited on the contact surfaces. The elimination of peroxide radicals out of titania gel and formation of anatase during heating are considered to be responsible for the improvement of apatite deposition ability.