Biomedical Engineering Reference
In-Depth Information
Figure 4.14.
MBCP Gel after four weeks of implantation in rabbit femoral epiphyses, SEM
using BSE showing the BCP particles (white) closely associated with bone trabeculae.
bone defects very easily, eliminating the need to shape the material to adjust it
to the implantation site. MBCP gel does not have the mechanical properties of
hydraulic bone cements. However, bone cells are able to invade the spaces cre-
ated by the disappearance of the polymer carrier (Figure 4.14). Bone ingrowth
takes place all around the granules at the expense of the resorption of the BCP
granules. In time, the mechanical properties are increased due to the presence of
the newly-formed bone [95-98]. Numerous reports both
in
vitro
and
in
vivo
have
confi rmed the effi cacy and performance of this concept for an injectable bone
substitute used in bone reconstruction [99 - 103].
4.4.8.2 Self-Hardening Injectable-Mouldable Composite.
IBS 2 [104,
105] is a self-hardening composite. The BCP granules are associated with si-
lanised hydrogel HPMC-Si. The guiding principle of silanised hydrogel HPMC-
Si is its hydrophilic and liquid property (it is viscous before being mixed with the
calcium phosphate load and injection) and its pH-controlled reticulation process.
The silanized hydrogel/calcium phosphate composite presented self reticulation
obtained by the change in pH as a catalyst and with an exothermic effect. Once
in the implantation site, in contact with the biological buffer liquids, a chemical
reaction without additive and without any catalyst allows bridging and reticula-
tion between the various macromolecular chains. This reaction is triggered by the
change in pH.
The advantage of ready-to-use mixtures is their easiness of use and the repro-
ducibility of the fi nal material. Their kinetics for osseous reconstruction can be
fast because of the many inter-granular paths. These materials have relatively few
intrinsic primary mechanical properties, even if the vehicles used harden by re-
ticulation. Achieving mechanical properties is secondary as it is obtained, thanks
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