ADHESTOP - EU funded project - Six european partners involved - ADHESTOP deals with the problem of catheter infections

Biomaterial

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Titanium as a biomaterial

Titanium was a laboratory curiosity until 1946, when Kroll developed a process for commercial production of titanium by reducing titaniumtetrachloride. Since that time the availability of titanium has prompted much work on the development of new and improved alloys as well as extensive evaluations of the properties of these materials. Rapid progress has been made in the development of medical instrumentation and surgical implants. The clinical success of titanium and its alloys (particularly the alloy with 6 wt% aluminium and 4 wt% vanadium) is due to some outstanding properties:

bulletTitanium is a reactive metal: in air, water, or arbitrary electrolytes a tenacious oxide layer is formed on the surface of the material. This oxide belongs to one of the most resistant compounds in the mineral world. As a dense film it protects the metal to chemical attack, also in the agressive biological environment.
bulletIn biological tissue titanium is inert: the oxide layer, that is in contact with the tissue, is hardly soluble and in particular no ions are released that could react with other molecules.
bulletThe mechanical properties of titanium compare favorably with those of other implantable metals and alloys. The yield strength is approximately the same as that of surgical quality 316L stainless steel and almost twice that of the familiar cast Co-Cr-Mo alloy used in orthopedic implants. The elastic modulus is approximately half that of the other common metal alloys used in surgery. This low modulus results in a material that is less rigid and deforms elastically under applied loads. This is important in the development of orthopedic products where a close match is desired between the elastic properties of long bone and the surgical implant. The fatique strength is about twice that of stainless steel.

The outstanding biocompatibility of titanium was already recognized by early researchers. Titanium has an extreme low toxicity and is well tolerated by both bone and soft tissue. Animal experiments have revealed that the material may be implanted for an extensive length of time; fibrous encapsulation of the implants is minimal to nonexistant. Histopathological examinations have failed to reveal any cellular changes adjacent to titanium implants. Careful examination of tissues adjacent to titanium have revealed neither giant cells nor macrophages, nor any other signs of inflammation. The material has been found to be safe in intravascular applications, owing to its high electronegativity and passive surface. For the same reason titanium does not cause hypersensitivity, which makes it the metal of choice in patients suspected of being sensitive to metals. For several decades, special titanium implants have been used with outstanding success in patients with histories of severe allergic reactions. Titanium implants are extensively used in cardiovascular, spinal surgery, orthopedic and dental surgery as well as in reconstructive and plastic surgery.

In view of the above mentioned, titanium fibre structures offer very promising possibilities for the development of a new peritoneal catheter.

 

 

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Last updated (dd/mm/yy) 09.12.2004.