Effects of alloying elements and surface treatments on the bioactivity of titanium-based alloys

Titanium (Ti) alloys are one of the most favored alloys in dental and orthopedic applications due to their superior properties such as low density, high specific strength, good corrosion resistance, and compatibility with the elastic modulus of cortical bone, preventing elastic mismatch issues. With the addition of different alloying elements, alloys such as Ti-6Al-4V, Ti-6Al-7Nb, and new generation high entropy alloys (HEAs) like TiTaHfNbZr have been developed. While these alloying elements enhance the mechanical properties of titanium, they play a decisive role in bioactivity of the alloy, specifically in the adsorption of calcium phosphate-based (CaP) structures on its surface. The other important parameter that influences the bioactivity of titanium is application of surface treatments such as alkali treatment, alkali+heat treatment which impact surface chemistry as well as surface topography tailoring methods such as laser surface processing. These surface treatments affect the surface properties of the alloy, particularly surface roughness, contact angle, and surface free energy. In this study, the effects of alloying elements and various surface treatments on the bioactivity of pure Ti, Ti-6Al-4V, Ti-6Al-7Nb, and high entropy TiTaHfNbZr alloys will be investigated.