Biomedical Engineering Reference
In-Depth Information
Inert
Resorbable
Rigid:
large Young's
modulus
Bioactive
Large
compression
strength and
lower tensile
strength
Tolerated by
the organism
Brittle:
failure without
plastic
deformation
Ceramics
High wetting
degree
Their surfaces
can be treated
to very high
polish limits
Favour cell
and tissue
adhesion
High surface
tension
7.2
General properties of ceramics as dense monoliths that make
them suitable as implants.
and very much lower tensile strength. in addition, they are stiff materials,
with a high Young's modulus, and are brittle because failure takes place
without plastic deformation. in relation to their surface properties, ceramics
show high degrees of wetting and surface tension which favour the adhesion
of proteins, cells and other biological moieties. Furthermore, the ceramic
surface can be treated to reach very high polish limits. However, as will
be explained latter, nowadays many research efforts are devoted towards
ceramics with interconnected porosity and in these cases the mechanical
properties will drastically change.
Concerning their reactivity inside the living body, bioceramics are
classified as almost bioinert, bioactive and resorbable. Figure 7.3 includes
the most important ceramics of each type as well as the clinical applications
of bioceramics. Bioactive ceramics are those where a sequence of reactions,
restricted only to the material surface, take place yielding a mechanically
strong bond between the bioceramic and the living tissues. almost bioinert
ceramics are considered to be first generation bioceramics whereas bioactive
and resorbable ceramics are known as second generation bioceramics.
6
the reactivity is a better criterion for classifying bioceramics than their
chemical composition or crystallinity. For instance, in the field of amorphous
ceramics, it is possible to obtain glasses that behave as bioinert, bioactive
or resorbable in the same chemical system depending on their different
compositions.
7
In addition, it is possible to find glasses with identical
composition behaving as bioinert when obtained by melting, or bioactive
