Implant applications of highly corrosion-resistant Ti-15Zr-4Nb-4Ta alloy

The release of metal ions from the Ti-15Zr-4Nb-4Ta alloy in pseudo body fluids was compared with those from Ti-6Al-4V and vanadium-free Ti-6Al-7Nb alloys widely used as implantable titanium alloys throughout the world, in order to choose an optimum acceleration solution for immersion testing. Bone plates, artificial hip joints of the cementless type and artificial tooth implants were experimentally fabricated using the Ti-15Zr-4Nb-4Ta alloy. The quantities of titanium ions released from the titanium alloys into phosphate-buffered saline, alpha-medium and fetal bovine serum were very small, and much lower than those released into 1.2 mass% L-cysteine, 0.05 mass%HCl and 1 mass% lactic acid solutions with lower pH values than the phosphate-buffered saline and a-medium. It was suggested that I mass% lactic acid solution was promising as an acceleration solution for immersion test. The quantities of titanium ions released from the Ti-15Zr-4Nb-4Ta alloy into fetal bovine serum, 1.2 mass% L-cysteine, 0.05 mass%HCl and 1 mass% lactic acid solutions were approximately 30% of those of titanium ions released from the Ti-6Al-4V alloy. The total quantity of zirconium, niobium and tantalum ions released from the Ti-15Zr-4Nb-4Ta alloy was much smaller than that of elements released from the Ti-6Al-4V and Ti-6Al-7Nb alloys. Bone plates, artificial hip joints and artificial tooth implants were successfully fabricated with the Ti-15Zr-4Nb-4Ta alloy using conventional manufacturing processes. The Ti-15Zr-4Nb-4Ta alloy with its excellent corrosion resistance is expected to become the preferential titanium alloy for implant applications in the future.