Titanium Implantation in the Human Body

Titanium Implantation in the Human Body

Titanium metal is an excellent material for the production of orthodontic, prosthetic, and cardiovascular implants due to its biocompatibility, low toxicity, high mechanical strength, and low density. All of these devices have to last an entire lifetime immersed in human body fluids without the possibility of inspection and maintenance, and therefore their corrosion resistance is a priority.

Titanium biocompatibility is strongly related to its corrosion resistance; in fact, lower corrosion means lower amounts of ions released into the human body, which may lead to prosthesis rejection. Moreover, it is possible to treat titanium surfaces by anodic oxidation, promoting the growth of its oxide, which, if properly tuned, can stimulate the growth of hydroxyapatite, one of the principal components of bone, thus further promoting biocompatibility.

The highly desired bone-like apatite formation on titanium is also reported to isolate the metal from the environment, enhancing corrosion resistance. Despite the fact that the growth of apatite requires a high degree of surface roughness, which may be detrimental to corrosion resistance, other requirements such as the presence of Ca and P ions and the growth of a thicker oxide can be beneficial. Thus ion implantation is a common and well-investigated technique to enhance the corrosion resistance of titanium.

Although very resistant, even titanium and its alloys can suffer corrosion in the human body: The presence of bacterial colonies such as those of Streptococcus in the oral environment are known to reduce titanium resistance, and fluoride ions present in toothpaste may be very dangerous for titanium.