Chp 13 - Chapter 13 Biomaterials 13.1 Introduction...

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13.1 Introduction Biomaterials are materials used in medicine and den- tistry that are intended to come in contact with liv- ing tissue. The familiar tooth rilling is where most humans first encounter biomaterials but increasingly many people now rely on more critical implants such as joint replacements, particularly hips, and cardiovas- cular repairs. Undoubtedly, these biomaterial implants improve the quality of life for an increasing number of people each year, not just for an ageing population with greater life expectancy, but for younger people with heart problems, injuries or inherited diseases. Biomaterials have now been successfully developed and used for more than a generation. First-generation biomaterials largely depended on being inert, or rel- atively inert, with minimal tissue response. For these materials a minimal fibrous layer forms between the biomaterials and the body when the material is not totally accepted by the body. The success of this type of implant depends largely on the selection of materi- als for their manufacture. Thus the now standard hip replacement (almost a million worldwide each year) initially used a multi-component assembly made with austenitic stainless steel for the stem, PMMA for fix- ation and polyethylene for the acetabular cup (see Figure 13.1). All the materials proved relatively bio- inert and gave an average life time of 10 years or more. Nowadays, while continuing with improved bio- inert materials, development has focused on bioactive materials which influence the biological response in a positive way, e.g. encourage bonding to surround- ing tissue with stimulation of new bone growth. With this bio-active approach the interface between the body cells and the implant is critical and the materials sci- ence of the biomaterials surface extremely important. In this chapter, various applications of biomaterials will be examined, from dental materials to drug deliv- ery systems. All types of materials are used in these applications and the criteria governing their selection Figure 13.1 Schematic diagram of a replacement hip joint. will be considered together with future development in the biomaterials field. 13.2 Requirements for biomaterials The requirements for a biomaterial are extremely demanding. Replacement or repair of a body feature, tissue, organ or function often necessitates the mate- rial used to have specialised mechanical, physical and chemical properties. However, the very first require- ment is biocompatibility with the human body, i.e. the ability of the material to perform with an appropriate host response. Unfortunately, no material is universally biocompatible, since a material may be biocompatible in one application but not with another. Biocompati- bility is therefore application specific. For the successful use of the biomaterial, consider-
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This note was uploaded on 12/05/2011 for the course MSE 4100 taught by Professor Hennig during the Fall '11 term at Cornell University (Engineering School).

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Chp 13 - Chapter 13 Biomaterials 13.1 Introduction...

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