The types and applications of medical titanium alloys

Titanium and titanium alloys are metallic materials that began to develop gradually in the middle of the 20th century. It has the characteristics of low density, high specific strength, good corrosion resistance, good biocompatibility and so on, and is widely used in aerospace, petrochemical and medical and health fields. As for the application of titanium in medical implants, as early as 1940, some scholars reported the inert performance between titanium implants and mouse femurs. In 1951, it was further demonstrated that pure titanium had better biocompatibility than other traditional implant materials. However, due to the high production cost of titanium alloy at that time and the maturity of stainless steel in implant market, the application development of titanium alloy in the medical field has been relatively slow.

Since the 1960s, pure titanium has been used in clinical oral research as a human implant. With the development of Ti-6Al-4V alloy with better performance, titanium alloy has been widely used in the medical implant market. Although the elastic modulus of Ti-6Al-4V is only about 114 GPa, lower than other biological materials such as stainless steel and cobalt-chromium alloy, it is still an order of magnitude higher than cortical bone (15~25GPa) and cancellous bone (0.05~3 GPa) in human body. Such a large difference can lead to a so-called stress-shielding effect, which in the long run can lead to bone resorption around the implant and even slide down the implant, reducing the success rate of bone implantation. At the same time, Al, V and other elements contained in its components are of certain biotoxicity. Long-term use in human body will cause lesions in the surrounding tissues of the implant and induce symptoms such as encephalopathy and anemia, which are not suitable for long-term use in human body. In recent years, for biological titanium alloys, researchers have developed such alloys as Gum alloy containing Ti-Nb-Ta-Zr, TLM alloy containing Ti-Nb-Zr-Mo-Sn and Ti2448 alloy containing Ti-Nb-Zr-Sn centering on non-toxic and low elastic modulus properties, etc. All these alloys adopted Nb, Zr, Mo and other elements with good biocompatibility. The experimental results showed that the biological performance of the Ti-6Al-4V and Ti-6Al-7Nb of such titanium alloys were superior to those of the traditional implants, such as bone promotion and sensitization.