Anodization of titanium alloys for orthopedic applications

Abstract

, 90 pages In recent years, nanostructured oxide films on titanium alloy surfaces have gained significant interest due to their electrical, catalytic and biological properties, leading to an extensive effort to engineer nanostructured oxide films on titanium and titanium alloy surfaces. In literature, there is a variety of different approaches to fabricate nanostructured oxide films, including hydrothermal treatment, sol-gel synthesis, physical vapor deposition, electrodeposition, and etc. Among these methods, electrochemical fabrication processes have widely been explored due to their flexibility to control surface morphology at the micronscale and nanoscale. Anodization technique, which allows fine-tuning of oxide film thickness, feature size, topography and chemistry, is the most popular electrochemical approach to fabricate nanostructured oxide films on titanium alloys, and has been investigated for orthopedic and biomedical applications by multiple research groups. Briefly, anodization is the growth of a controlled oxide film on the surface of a metallic component attached to the anode of an electrochemical cell. This thesis explores the use of anodization of titanium alloys for orthopedic applications. vii In this thesis, micropit structures were grown on Ti6Al4V surfaces via anodization using fluoride free electrolytes consisting of NH4Cl in distilled water. Furthermore, nanotubular structures were fabricated via anodization of Ti6Al7Nb surfaces in fluoride electrolyte. Fabricated surface structures were characterized for their physical and chemical properties and the bioactivity of the surfaces were determined by soaking samples in simulated body fluid up to 30 days. The thesis concludes with areas requiring further research to successfully translate anodized titanium alloys to clinics for orthopedic applications.

Treatments for enhancing the biocompatibility of titanium implants

“…Nanotubular films are bound to the titanium surface by the chemical-thermal method of anodization. There are changes in the microstructure of the titanium oxide crystals 81 . The resulting morphology of the tubular oxide layer can be achieved by adjusting appropriate parameters, i.e.…”

“…A variable nanostructure of the titanium coating can be achieved by applying various currents, but the optimum topography has not yet been determined 85 . In vitro and in vivo tests point to enhanced bone cell functions and good osseointegration, leading to a reduced risk of implant failure 81 .…”

Controlling morphological parameters of a nanotubular TiO2 coating layer prepared by anodic oxidation

“…Common surface modifications can be made through coatings with materials with osteoinductive characteristics such as hydroxyapatite or other calcium phosphate compounds, or with morphological modifications such as blasting (which will produce a micrometer roughness) or anodic oxidation [1,5]. Anodic oxidation or anodizing is a promising modification used to produce a nanostructured titanium oxide (TiO 2 ) coating layer in the form of self-ordered vertically aligned nanotubes (or nanotubular TiO 2 ) on titanium implant devices [6].…”

“…Zwilling et al, in a pioneering study, has produced nanotubular TiO 2 arrays on metallic titanium via anodic oxidation in a chromic acid electrolyte containing hydrofluoric acid [7]. Thereafter, anodizing has become a well-known method for the production of nanotubular TiO 2 [6,8]. This is an attractive procedure due to its ease of implementation and low cost.…”

“…There are many works reporting an increase in cell adhesion and proliferation in the presence of nanostructured surface compared to smooth titanium surface. However, there is no consensus about which nanotube diameter is more effective for cell response [6,[13][14][15][16].…”