Abstract
Apatite depositions from simulated body fluid (SBF) have been widely used for the in vitro assessment of the bioactivity of bone- and dental-implant materials. In previous work, we reported that titanium-based implant materials can be coated with an anodic TiO2 nanotube layer which can significantly stimulate apatite formation. In the present work, we demonstrate that the tubular nature of such coatings makes them highly suitable for the application of a treatment called "alternative immersion method (AIM)", which preloads the coatings with synthetic hydroxyapatite. This treatment is indeed found to additionally promote natural apatite formation significantly. To study the AIM effect, layers of nanotubes with various diameters and crystal structures (amorphous, anatase/rutile) were produced, AIM-treated, and the formation of apatite in SBF10 (10 mmol l(-1) HCO3-) was evaluated. The results show a drastic enhancement of apatite deposition rates (in some cases >20-fold acceleration) for AIM-treated TiO2 nanotube layers in comparison with non-treated TiO2 surfaces. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.