Enhancement of apatite formation on Ti-50Zr alloy in simulated body environment

Abstract

Ti-50Zr alloy is 2.5 times as strong as pure Ti and has a lower Young's modulus, making it a useful material for repairing bone and teeth. However, Ti-50Zr alloy has a limited ability to bond with bone in vivo. Under biological conditions, apatite formation at the surface of a Ti or alloy implant is necessary for its bonding with bone. Various approaches to surface modification have been proposed to impart bone-bonding ability to Ti-50Zr alloy; however, there remains a need for further improvements to the alloy's apatiteforming ability. Hence, in this study, we compared apatite formation at the surface of alloy substrates in simulated body fluid, after various surface treatments. Treatment with 5 M NaOH followed by 1 M CaCl2 was the most effective procedure, whereas a sample subjected to a hot water post-treatment formed less apatite. Notably, no apatite formed on samples treated with 10 M NaOH.

Development of Rapid Bioactivity-Expressed Zr-50Ti Alloys by Surface Treatment with Modified Simulated Body Fluid

“…On the other hand, despite the bioactivity imparted to the substrate material, the apatite formed in SBF bonds with the metallic substrate with weak strength, leading to a risk of the apatite coating peeling off. Miyazaki et al reported that although apatite can successfully precipitate on the Zr-50Ti alloys, the adhesive strength between apatite and the surface of Zr-50Ti alloys is insufficient [ 15 ]. According to the F1147-05 regulation of the American Society for Testing and Materials (ASTM) for calcium phosphate and metallic coatings, a minimum adhesion strength of 22 MPa is suitable for orthopedic applications.…”