survey conducted in 1988
indicates that more than 11 million people in the United States have biomaterial implants [Moss et al., 19911. A biomaterial is defined here as any material used in the body to achieve a therapeutic or diagnostic purpose. Biomaterial-containing implants range from artificial heart valves, arteries and veins to artificial joints, drug delivery systems, and silicone implants. The survey did not include dental restorative procedures and devices that may apply to nearly the entire U.S. population. The numbers and variety of these products speak to the importance of biomaterials and biomaterialcontaining medical devices for our national health.
Although many functionally sufficient materials are in use, chronic problems have been recognized with different types of materials and their applications. Materials may be limited in their use for a number of reasons, including poor biocompatibility, infection susceptibility, immune responses, thrombus formation, limited biodurability, and elicitation of cellular degradatory responses. There is, therefore, a critical need for biomaterials that provide longer-term clinical benefit and fewer complications for patients requiring acute or chronic biomaterialcontaining implants. A reduction in implantrelated complications of 2% would enhance the quality of life and reduce costs for an estimated 100,000 to 200,000 new patients each year.