Why is titanium used for body implants??

Question

Why is titanium used for body implants??

Answer 1

it's strong durable and less likely to be rejected

Answer 2

In 1952 Professor Per-Ingvar Branemark, M.D. made a discovery by accident. A physician and researcher interested in wound healing.  Dr. Branemark was using live rabbits to study bone biology.  He inserted tiny metal tubes into the rabbits' bones so that he culd place a microscope to study bone tissue. He chose titanium because of of it being a light, strong, non-corrosive metal.  After several months he attempted to remove the titanium sleeves from the rabbits bones and was surprised to discover that he was unable to extract them.The titanium had formed an irreversible bond with living bone.  

His curiosity aroused, Dr. Branemark demonstrated that under carefully controlled conditions, titanium bonded to the bones with a very high degree of predictability.  Titanium did not appear to cause inflammation in surrounding soft tissue, nor was it rejected by living bone.  Branemark named this process of bone bonding to the titanium osseointegration.  The first applications for titanium was in dental implants in 1965 but it wasn't until 1982 that the food and drug administration gave approval for use for titanium in dental implants in the United States. From then on other applications have been developed for joints, metal pins in broken bones and so forth.

Answer 3

-It doesn't get attacked/rejected by human body as much as some other materials...part of this is 'cause it tends to make a rather thin oxide (~TiO2) film. The wordy people like calling this kinda thing biocompatibility.

-strength to mass ratio...

-also stiff (stiff/mass). While this is good for being able to use less material, it can also kind of shield the natural bone from stresses that it would otherwise be put under. This can mess up the growing & remodeling that goes on.

-You can actually make stuff with it (you can sinter it, anneal/heat treat it, work it, alloy it, etc...)

Answer 4

The high strength, low weight, outstanding corrosion resistance possessed by titanium and titanium alloys have led to a wide and diversified range of successful applications which demand high levels of reliable performance in surgery and medicine as well as in aerospace, automotive, chemical plant, power generation, oil and gas extraction, sports, and other major industries.

Suitability of Titanium for Implant Purposes

More than 1000 tonnes (2.2 million pounds) of titanium devices of every description and function are implanted in patients worldwide every year. Requirements for joint replacement continue to grow as people live longer or damage themselves more through hard sports play or jogging, or are seriously injured in road traffic and other accidents. Light, strong and totally biocompatible, titanium is one of few materials that naturally match the requirements for implantation in the human body

Medical grade titanium alloys have a significantly higher strength to weight ratio than competing stainless steels. The range of available titanium alloys enables medical specialists designers to select materials and forms closely tailored to the needs of the application. The full range of alloys reaches from high ductility commercially pure titanium used where extreme formability is essential, to fully heat treatable alloys with strength above 1300 MPa, (190ksi). Shape-memory alloys based on titanium, further extend the range of useful properties and applications. A combination of forging or casting, machining and fabrication are the process routes used for medical products. Surface engineering frequently plays a significant role, extending the performance of titanium several times beyond its natural capability.

Titanium Performance in Medical Applications

‘Fit and forget’, is an essential requirement where equipment in critical applications, once installed, cannot readily be maintained or replaced. There is no more challenging use in this respect than implants in the human body. Here, the effectiveness and reliability of implants, and medical and surgical instruments and devices is an essential factor in saving lives and in the long term relief of suffering and pain. Implantation represents a potential assault on the chemical, physiological and mechanical structure of the human body. There is nothing comparable to a metallic implant in living tissue. Most metals in body fluids and tissue are found in stable organic complexes. Corrosion of implanted metal by body fluids, results in the release of unwanted metallic ions, with likely interference in the processes of life. Corrosion resistance is not sufficient of itself to suppress the body’s reaction to cell toxic metals or allergenic elements such as nickel, and even in very small concentrations from a minimum level of corrosion, these may initiate rejection reactions. Titanium is judged to be completely inert and immune to corrosion by all body fluids and tissue, and is thus wholly bio-compatible.

The natural selection of titanium for implantation is determined by a combination of most favourable characteristics including immunity to corrosion, bio-compatibility, strength, low modulus and density and the capacity for joining with bone and other tissue - osseointegration. The mechanical and physical properties of titanium alloys combine to provide implants which are highly damage tolerant. The human anatomy naturally limits the shape and allowable volume of implants. The lower modulus of titanium alloys compared to steel is a positive factor in reducing bone resorbtion. Two further parameters define the usefulness of the implantable alloy, the notch sensitivity, - the ratio of tensile strength in the notched vs un-notched condition, and the resistance to crack propagation, or fracture toughness. Titanium scores well in both cases. Typical NS/TS ratios for titanium and its alloys are 1.4 - 1.7 (1.1 is a minimum for an acceptable implant material). Fracture toughness of all high strength implantable alloys is above 50MPa.m-½ with critical crack lengths well above the minimum for detection by standard methods of non-destructive testing.