Biomedical Engineering Reference
In-Depth Information
of modern types of calcium orthophosphate bioceramics. For
some clinical applications, such as cranioplasty, a relatively slow
resorption and replacement by bone is quite acceptable, whereas
in other applications, such as periodontal bone defects repair, sinus
lift, etc., the ability of the hardened cement to be replaced quickly
by bone is crucial. Experimental results suggest that a number of
parameters of the self-setting calcium orthophosphate formulations,
such as the Ca/P ionic ratio, carbonate content, ionic substitution,
crystallinity, etc. might affect the dissolution characteristics of the
cements in slightly acidic solutions. This gives an opportunity to
formulate compositions, possessing different resorption rates,
which is suited for different biomedical applications [143, 144].
The discovery of self-setting calcium orthophosphate
formulations has already opened up new perspectives in synthesis
of bioceramic scaffolds, possessing sufficient mechanical properties
[298, 302, 303, 412]. In the past, such scaffolds could only be
manufactured by the sintering route at elevated temperatures
[601]. Therefore, until recently it was impossible to produce
resorbable preset low-temperature hydrated 3D bioceramics
for various applications, e.g.,
scaffolds and granules, from low-
temperature calcium orthophosphate phases, such as ACP, DCPA,
DCPD, OCP and CDHA. Now, using the appropriate techniques,
open macroporous 3D scaffolds consisting of the aforementioned
low-temperature phases (currently, excluding ACP and OCP) can
be produced via a cementitious reaction [297, 327, 333, 334, 412,
602-604], thus dramatically widening the application of these
calcium orthophosphates as biomaterials and bioceramics. This
type of biomaterials could be very promising for tissue engineering
applications. Among them, CDHA is of a special interest due to its
chemical similarity to bone material and a large specific surface
area.
To conclude this part, one should stress, that the most
promising direction of the future developments of self-setting
calcium orthophosphate formulations is obviously seen in their
functionalization by incorporation or impregnation of various
hormones, growth factors, drugs, other bioorganic compounds, as
well as incorporation of living cells and/or other tiny biological
objects [605-616]. For example, silk fibroin can regular the
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