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Polymer-based biomaterials have been used in a variety of medical applications, including artificial surgical implants. Their use has been made possible by the emergence of new synthetic materials, new engineering processes, and medical improvement in approaches to medical intervention with regard to infection and rejection of foreign substances by the human host. This article describes the development of these materials since the 1920s.
INTRODUCTION
Biomaterials are biologically inert or compatible materials placed inside a patient on a long-term or permanent basis. Until early this century, plants, ore, and animal sources were the only materials used in the practice of wound closure and dental repair.l-5 Since then, science and medicine have made considerable progress. For more than 50 years, tremendous advances have taken place in medical devices that function on contact with living tissues. Advances in engineering and a greater availability of synthetic materials triggered the development of engineered polymers for use in biomaterials medical devices.6 A number of milestones have been possible because antibiotics and other drugs have lessened the risk of infection and rejection, and research on the structure and function of biomaterials has taken an engineering focus. Today, new materials last longer and perform better.
Among all biomaterials, polymerbased materials offer the greatest versatility in properties and processing. They have addressed dental, neurological, cardiovascular, ophthalmic, and reconstructive pathologies with implantable devices designed to sustain or enhance life. They have also been found useful in temporary therapies such as hemodialysis, coronary angioplasty, blood oxygenation, electrosurgery, and wound treatment.l-3
POLYMERS
The main feature that sets polymers apart from other materials is that polymers are made of long molecules. They contain a chain of atoms held together by covalent bonds, with carbon normally being in a high proportion. The carbon atoms are connected to form long chains and extensive networks, which form a backbone for the structure. Attached to this backbone are hydrogen atoms in organic and inorganic groups. Geometrically, the long polymer molecules can be linear, branched, or a three-dimensional network. The molecular architecture of a polymer determines the properties of the material.
Polymers are typically classified in three groups: thermoplastics, rubbers, and thermosets. Thermoplastics, which are often referred to as "plastics," are linear or branched polymers that can be melted upon the application of...