Biomedical Engineering Reference
In-Depth Information
5
Properties and characterisation of
bone repair materials
A. A. White and S. M. B e S t,
University of Cambridge, UK
Abstract
: this chapter discusses material properties and characterisation,
focusing on how to manipulate a material's properties through changes
in chemistry, microstructure and processing; the relevant techniques to
characterise the material thoroughly; and the interrelationship between
different levels and types of material properties. the four main sections
discuss (1) mechanical properties, (2) molecular and microstructural
properties, (3) physiological effects and (4) the strengths and weakness of
different material classes and their applications.
Key words
: material characterisation, material properties, mechanical
properties, microstructure, physiological effects.
5.1 Introduction
to perform successfully
in vivo
, an implant material must possess particular
and well-controlled properties suited to each individual application. in major
load-bearing situations, such as joint replacement, emphasis may be placed
on the strength of the material and its ability to withstand repeated cycles
of loading and unloading. the focus in repairing small bone defects, on the
other hand, may lie on the chemical composition of the material and whether
it is able to bond with surrounding bone tissue or trigger new growth.
While emphasis may be placed on one area, say strength, the situation
is not so simple as to be able choose the strongest available material and
implant it. We must first have an understanding of what microstructural
properties influence that strength, and how to control them, and we must
consider how susceptible that material's chemistry is to alterations in the
body's environment. What, at first glance, may seem like the ideal material,
could fail catastrophically when placed in the body. the better choice may
be a weaker material that is inherently less susceptible to degradation
in
vivo
, but whose microstructure can be altered to make it stronger and thus
the more successful implant material for that application.
the important things to understand are (1) how to manipulate a material's
characteristics through changes in chemistry, microstructure and processing;
(2) the relevant techniques to characterise the material's properties thoroughly
and (3) the interrelationship between different levels and types of material
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