Materials Challenge: Implants
"I am Titanium"
For centuries, humans have been searching for materials to replace damaged or failed human tissue. These tissue replacements, or implants, have included everything from bits of shell hammered into the jaw to replace missing teeth to the metal hip and knee replacements we see today. There are many unique challenges in selecting materials for implants, as in addition to having properties similar to the failed biological component the implant must repair or replace, any material used must not be toxic to the human body. Titanium is a commonly used material in implants because it is strong, durable, and bonds with bone. It is not perfect, however, the high Young's modulus, or stiffness, of titanium can result in stress shielding -- where the implant bears more of the body's load than the surrounding bone, causing the bone tissue to weaken and fracture.
Our video will provide an introduction to implants by defining the term, giving a brief history of the development of implants, and giving some examples of the types of implants used today. We will then discuss the specific properties required of implants, including strength, durability and biocompatibility. We will then discuss titanium implants specifically -- the properties of titanium, what makes it work well for implants, as well as some of the challenges associated with the use of titanium and its alloys. We will discuss stress shielding in more detail, and demonstrate cold working -- a process by which the yield strength of metals can be increased without affecting the Young's modulus.
1. Arsenjev, A. P.; Arsenjev, P. A.; Evdokimov, A. A.; Makaricheva, E. U.; Sheinin, M. J., "The processing of surgical implants from pure titanium," Biomedical Engineering Conference, 1996., Proceedings of the 1996 Fifteenth Southern , vol., no., pp.384,385, 29-31 Mar 1996 http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=493256&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D493256
2. C.N. Elias, J.H.C. Lima, R. Valiev, and M.A. Meyers. "Biomedical Uses of Titanium and its Alloys". JOM, March 2008. Pgs 46-49. http://www.meyersgroup.ucsd.edu/papers/journals/meyers%20316.pdf
3. M. Niinomi and M. Nakai, "Titanium-Based Biomaterials for Preventing Stress Shielding between Implant Devices and Bone," International Journal of Biomaterials, vol. 2011, Article ID 836587, 10 pages, 2011. http://www.hindawi.com/journals/ijbm/2011/836587/
4. Neailey, K., and Pond, R.C. (1982). Metal implants. Materials & Design, Volume 3, Issue 3, Pages 470-478. http://www.sciencedirect.com/science/article/pii/0261306982901133.
5. Springer Science+Business Media. (2011, July 26). Heavy metal: Titanium implant safety under scrutiny. ScienceDaily. Retrieved May 5, 2014 from www.sciencedaily.com/releases/2011/07/110725101257.htm
6. Slides from a Materials Science/Biomaterials Course; details processes, properties and uses of metallic biomaterials: http://www.bioen.utah.edu/faculty/pat/Courses/biomaterials2006/Metals%20and%20Applications%20in%20Orthopedics.pdf
7. How It's Made (YouTube clip): Titanium Dental Implants https://www.youtube.com/watch?v=S4j_GOYFoG8
All unoriginal images were unlicensed and accessed through Wikipedia.
Titanium by David Guetta ft. Sia