Anodization: A Promising Nano-Modification Technique

As one of the valve metals (including Ti, Al, Ta, Nb, V, Hf, W), titanium is protected by a thin titanium oxide layer which spontaneously forms on its surface when exposed to air or other oxygen containing environments. This oxide passive layer is typically 2 to 5 nm thick and is responsible for the well-documented corrosion resistance property of titanium and its alloys. Because of this and their excellent mechanical properties, titanium and its alloys are widely used in orthopedic and dental applications. However, the native TiO2 layer is not bioactive enough to form a direct bonding with bone, which means the lack of osseointegration to juxtaposed bone might lead to long term failure after implantation. Specifically, the 10 to 15 year lifetime of current titanium-based orthopedic implants is not as long as expected by many patients. 3 As a result, many attempts have been made to improve the surface properties of titanium-based implants (e.g., topography, chemistry and surface energy), which directly determine the implant-environment interactions after implantation. These surface modification techniques include mechanical methods (e.g., sand-blasting), chemical methods (e.g., acid etching), coatings (e.g., plasma spraying), etc. Through these conventional approaches, a better bonding ability with bone has been achieved due to the creation of a optimum micro-scale surface roughness, a more favorable surface chemistry, and/or a new morphology preferred by bone-forming cells (or osteoblasts). However, neither these mechanical nor chemical methods have the ability to produce controlled surface topographies. Moreover, these methods have the of Titanium-based Implants for Orthopedic Applications