Using Citric-Acid-Based Anodization to Form Magnesium-Doped Carbonated Apatite-Containing Oxides on Solid and 3D-Printed Titanium Substrates

With increasing life expectancy and an aging global population, the demand for orthopedic and dental implants is increasing. Recently developed, citric-acid-based anodization processes facilitate the production of more bioactive oxide layers by incorporating important bone minerals such as Ca, P, and Mg and forming bone-like crystalline compounds such as carbonated apatite on titanium implant materials. The primary goal of the present study was to evaluate the applicability of these anodization processes to solid and 3D-printed titanium alloy substrates. The anodized oxides produced on each solid or 3D-printed lattice substrate revealed multi-scaled surface roughness profiles as evidenced by scanning electron microscopy, optical microscopy, and surface roughness analyses. Additionally, each oxide group was shown to incorporate substantial amounts of Ca, P, and Mg bone-mineral dopants and form AB-type carbonated apatite, as shown using a combination of energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and attenuated total reflectance–Fourier transform infrared spectroscopy analyses. Finally, each oxide group showed sustained Ca, P, and Mg ion release during an inductively coupled plasma spectroscopy dissolution assessment, and demonstrated early apatite-forming ability during simulated body fluid bioactivity testing. The findings of this study show much promise for the applicability of these novel oxide coatings to a wide variety of future titanium implant applications.