Crystallization of amorphous titania gel by hot water aging and induction of in vitro apatite formation by crystallized titania

Surface modification of titanium implants by introducing a titania layer on their surface is an effective approach to provide bioinert titanium with bioactivity, i.e., the ability to bond directly and tightly to the surrounding hard tissue through the formation of a thin layer of apatite after implantation in the human body. The crystalline structure and abundance of Ti–OH functional groups have been found to contribute to the ability of titania gel to initiate apatite deposition on titanium in human physiological fluid. In the current investigation, an amorphous titania gel was firstly introduced on titanium surface by oxidizing the titanium substrate with hydrogen peroxide. Well-crystallized anatase films incorporated with abundant Ti–OH groups were then produced simply through a subsequent hot water aging of the amorphous titania gel. Results obtained in this investigation suggested that the low-temperature crystallization of titania proceeded in a dissolution–precipitation process. Titanium treated by the present low-temperature chemical modification technique induced significant apatite deposition within 24 h in a simulated body fluid (SBF).