Surface Properties of Ti65Zr Alloy Modified with TiZr Oxide and Hydroxyapatite

Titanium-zirconium dioxide nanostructures loaded by hydroxyapatite were produced on the surface of Ti65Zr alloy. The alloy was treated by anodization with the subsequent immersion in calcium glycerophosphate (CG) solutions. The resulting surfaces present TiO2-ZrO2 nanotubular (TiZr-NT) structures enriched with hydroxyapatite (HAP). The nanotube texture is expected to enhance the surface's corrosion resistance and promote integration with bone tissue in dental implants. The TiZr-NT structure had a diameter of 73 ± 2.2 nm and a length of 10.1 ± 0.5 μm. The most favorable result for the growth of HAP in Hanks' balanced salt solution (Hanks' BSS) was obtained at a CG concentration of 0.5 g/L. Samples soaked in CG at a concentration of 0.5 g/L demonstrated in a decrease of the contact angles to 25.2°; after 3 days of exposure to Hanks' BSS, the contact angles further reduced to 18.5°. The corrosion studies also showed that the TiZr-NT structure soaked in the CG = 0.5 g/L solution exhibited the best corrosion stability.

Synthesis of Titanium Oxide Nanotubes Loaded with Hydroxyapatite

A simple method of synthesis of TiO2 nanotubes (TiNT) loaded with hydroxyapatite (HAP) is described. Such nanotubes find wide applications in various fields, including biomedicine, solar cells, and drug delivery, due to their bioactivity and potential for osseointegration. The Cp-Ti substrate was anodized at a constant voltage of 40 V, with the subsequent heat treatment at 450 °C. The resulting TiNT had a diameter of 100.3 ± 2.8 nm and a length of 3.5 ± 0.04 μm. The best result of the growth rate of HAP in Hanks' balanced salt solution (Hanks' BSS) was obtained in calcium glycerophosphate (CG = 0.1 g/L) when precipitates formed on the bottom and walls of the nanotubes. Structural properties, surface wettability, corrosion resistance, and growth rate of HAP as an indicator of the bioactivity of the coating have been studied. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), potentiodynamic polarization test (PPC), electrochemical impedance spectroscopy (EIS), and contact angle (CA) measurements were used to characterize HAP-loaded nanotubes (HAP-TiNT). The CA, also serving as an indirect indicator of bioactivity, was 30.4 ± 1.1° for the TiNT not containing HAP. The contact angle value for HAP-TiNT produced in 0.1 g/L CG was 18.2 ± 1.2°, and for HAP-TiNT exposed to Hanks' BSS for 7 days, the CA was 7.2 ± 0.5°. The corrosion studies and measurement of HAP growth rates after a 7-day exposure to Hanks' BSS confirmed the result that TiNT processed in 0.1 g/L of CG exhibited the most significant capacity for HAP formation compared to the other tested samples.