FUNDAMENTALS OF BIOMATERIALS AND BIOCOMPATIBILITY - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 3

1.1 OVERVIEW
In last two decades, impressive progress has been recorded in terms of developing
new materials or refi ning existing material composition and microstructure in
order to obtain better performance of designed materials in biomedical appli-
cations. The success of such large efforts clearly demands better understanding
of various concepts such as biocompatibility, host response, and cell-biomaterial
interaction. This chapter reviews the fundamentals for understanding biomateri-
als development.
1.2 INTRODUCTION
One of the most exciting and rewarding research areas of materials science
involves the applications of materials to health care, especially to reconstructive
surgery. The importance of biomaterials can be well realized from an economical
aspect, that is, in terms of an estimate of total health care expenditure around the
world. In the most developed country of the world, the United States, total health
care expenditure in the year 2000 was approximately 14 billion US dollars. It was
also reported that the US market for biomaterials in 2000 was 9 billion US dollars.
It can be further noted that the respective annual expenses in other countries of
the world are typically around two-to-three times that of the US expenses 1 . With
continuous changes in lifestyle as well as in global scenarios in the health sector,
such expenses are defi nitely on a much higher side today in both developed and,
more importantly, developing nations, than at the beginning of this century. To
this end, the development of biomaterials and related devices is important.
The fi eld of biomaterials is multidisciplinary, and the design of biomaterials
requires the synergistic interaction of materials science, biological science, chemi-
cal science, medical science and mechanical science. Such interaction has been
schematically illustrated in Figure 1.1. Also shown in Figure 1.1 is the necessity to
develop cross-disciplinary approaches in designing new biomaterials. Among dif-
ferent kinds of biomaterials 2 , metals and metallic alloys are used in orthopedics,
dentistry and other load-bearing applications; ceramics are used 3 with emphasis
on either their chemically inert 4 nature or their high bioactivity 5 ; polymers are
used for soft tissue replacement and research is also being pursued for application
in hard tissue replacement. To achieve better biological properties and mechani-
cal strength, composite materials of metals, ceramics and polymers are being de-
veloped and clinically assessed to a limited extent. Broadly, all biomaterials are
being developed to maintain a balance between the mechanical properties of the
replaced tissues and the biochemical effects of the material on the tissue. Both
areas are of great importance as far as the clinical success of materials is con-
cerned. However, in most (if not all) biological systems, a range of properties
is required, such as biological activity, mechanical strength, chemical durability,
and so forth. Therefore, a clinical need often can only be fulfi lled by a designed
material that exhibits a complex combination of some of the above mentioned
properties. Figure 1.2 shows the different organs of a living human body that can