Biomedical Engineering Reference
In-Depth Information
Al 2 O 3 - K 2 O - B 2 O 3 -F glass ceramics and stabilized ZrO 2 based bioinert ceramics
are summarized. The physical as well as tribological properties of polyethylene
(PE) based hybrid biocomposites are discussed to illustrate the concept of how
physical/wear properties can be enhanced along with biocompatibility due to
combined addition of bioinert and bioactive ceramic to a bioinert polymeric
matrix. The tribological and corrosion properties of some important orthopedic
metallic alloys based on Ti or Co-Cr-Mo are also illustrated. Finally, a summary
presents the future perspective on orthopedic biomaterials development and
some unresolved issues.
3.2 INTRODUCTION
The recent development in scientifi c understanding, particularly in the area of
material science and biological science, has enabled an impressive progress in
developing new biomaterials. In the last few decades, materials for biomedical
applications have received greater attention in the scientifi c community, primar-
ily due to the fact that suitably designed biomaterials are capable of replacing,
reconstructing and regenerating human and animal body tissues for long term
use, without much toxic or infl ammation effects. In specifi c applications, such as
hard tissue replacements, materials 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 concerned. However, in most (if not all) bio-
logical systems, a range of properties is required, such as biological activity,
mechanical strength, chemical durability, and so on. Therefore, often a clinical
need can only be fulfi lled by a designed material, which exhibits a complex com-
bination of properties.
Various examples of current usage of orthopedic biomaterials include joints
(knee, hip, ankle, and so on), bone fi lling materials or bone spacers. The develop-
ment of new biomaterials not only extends toward monolithic bulk materials but
also composites of different classes of materials along with coating. The major
issues in the development of biocompatible coatings are the coating/bio interface
adhesion as well as lifetime of coatings, being limited by factors like non-uniform
coating thickness, delamination due to mismatching of co-effi cient of thermal
expansion (CTE) and weak interface bonding between metal substrate and
phosphate coatings 1 . Among different kinds of biomaterials, ceramics are used
as bone - fi lling material and load-bearing components in various orthopedic joint
replacements. To achieve better chemical resistance and mechanical strength,
various composites, such as metal-ceramic, ceramic-polymer and ceramic-
ceramic, are being developed. In designing composites, it is important to optimize
composite composition as well as microstructure/phase assemblage for a specifi c
tissue replacement application. Among various bioceramic materials, HAp,
having similar mineral composition to bone and teeth, is widely studied for vari-
ous applications requiring good bioactive property 2 . Although HAp is a highly
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