A comparative study of in vitro apatite deposition on heat-, H2O2-, and NaOH-treated titanium surfaces

Commercially pure titanium specimens are subjected to three different treat ments, and their bioactivity are evaluated by immersing the specimens in a simulated body fluid (SBF, Kokubo's recipe) for various periods up to 7 day s, with particular attention being paid to the differences in apatite depos ition between surfaces open to SBF and surfaces in contact with the contain er's bottom. The treatment with a H2O2/HCl solution at 80 degreesC for 30 m in followed by heating at 400 degreesC for 1 h produces an anatase titania gel layer on the specimen surface. This gel layer deposits apatite both on the contact and on open surfaces, and apatite deposition ability does not c hange with pre-staking in distilled water. The treatment with a NaOH soluti on at 60 degreesC for 3 days produces a sodium titanate gel layer. This gel layer can deposit apatite only on the contact surface, and the apatite dep osition ability is completely lost after 1 day of pre-staking in distilled water. It is concluded, therefore, that the bioactivity of the titania gel originates from the favorable structure of the gel itself while the bioacti vity of the sodium titanate gel depends heavily on ion release from the gel . The third treatment, a simple heat treatment at 400 degreesC for 1 h, pro duces a dense (not porous) oxide layer on the specimen surface. The specime ns can deposit apatite on the contact surface after only 3 days of staking in SBF, but they cannot deposit apatite on the open surface for up to 2 mon ths of staking. The implications of such apatite deposition behavior have b een discussed in relation to the environments of titanium implants in bone as well as to the methodology of the SBF staking experiment. (C) 2000 John Wiley & Sons, Inc.