Biomedical Engineering Reference
In-Depth Information
6
Metals as bone repair materials
J. L. GonzáLez-CarrasCo, Centro nacional
de Investigaciones Metalúrgicas (CenIM-CsIC) and
CIBer-BBn, spain
Abstract
:
Metals are the materials of choice for many structural implantable
device applications and there is no reason to expect a change in the short
or medium term. Processing-structure relations
are described with special
emphasis on Ti and Ti-base alloys, austenitic stainless steel and Co-based
alloys, but other metallic materials in use are also presented. Mechanical
properties and their relationship with the microstructure are summarized
for static and dynamic loads. Chemical properties focus on corrosion
behaviour, the nature of the passive films and the closely related ion release.
surface energy and surface charges, which are relevant for understanding
the biological response, are also discussed. a detailed overview of the new
family of Ti-base alloys with a lower Young's modulus, ni-free Fe-based
alloys, nanostructured alloys, biodegradable alloys and porous metals for the
fabrication of scaffolds, is presented.
Key words
:
biodegradable alloys, Co-based alloys, corrosion behaviour,
magnetic metallic materials, mechanical properties, metallic scaffolds, ni-
free alloys, shape memory alloys, stainless steels, Ti-base alloys, trends in
metallic biomaterials.
6.1 Introduction
Materials in use within the body cover a wide spectrum, with examples
of metals, ceramics, glasses, polymers and composites. Physical, chemical
and mechanical characteristics make some materials more desirable than
others.
The low Young's modulus and the viscoelastic nature of synthetic polymers
often caused them to be excluded from load-bearing applications. Furthermore,
it is very difficult to obtain medical grade polymers free of additives. The
release of these additives under physiological constraints may lead to toxic
or allergic processes.
Ceramics have been recognized as biomaterials particularly because of
their good biocompatibility. Monolithic ceramics, however, are inherently
brittle and fabrication is constricted, especially when considering recent
improvements in prosthesis design. The inherent brittleness tends to limit
their applications to devices where the loads are predominantly compressive
in nature or as coatings.
Metals and their alloys are the biomaterials of choice as cyclic load-bearing
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