Biomedical Engineering Reference
In-Depth Information
calcium orthophosphates. Small amounts of bone-like apatite might
be easily prepared by crystallization from SBF and rSBF but what can
be said about larger quantities? A standard way of the concentration
increasing causes chemical changes in the precipitates [927]. After a
necessary technology is developed, one will have to think on scaffold
preparation from this material, keeping in mind that any thermal
treatment would destroy this material. A spark plasma sintering
approach based on the use of pulsed current and enabling very fast
heating and cooling rates seemed to be a first hint to achieve this
goal [964]. However, a rapid development of the self-setting calcium
orthophosphate formulations (Chapter 5), which can be easily
doped by the necessary chemical elements, seems to be a better
solution of this problem. Furthermore, the existence of OA remains
to be questionable, as well as the bioactivity mechanism of calcium
orthophosphates requires better understanding.
To date, although calcium orthophosphate biomaterials and
bioceramics have been extensively studied for over 50 years, their
ability to trigger bone formation is still incomparable with other
biomaterials. Naturally, the biomaterials' field is shifting towards
biologically active systems in order to improve their performance
and to expand their use [965]. Due to this case, tissue engineering
is the strongest direction of current research, which, in the case of
calcium orthophosphates, means fabrication of proper substrates
and/or scaffolds to carry cells, hormones and biochemical factors to
be further used in surgery and medicine. Presumably, a synthesis of
various types of calcium orthophosphate-based biocomposites and
hybrid biomaterials (Chapter 6) occupies the second important place.
For example, even composites with carbon nanotubes already exist
[966-968]! The third important place is occupied by investigations
devoted to the synthesis and characterization of various nano-sized
particles and nanodimensional crystals of calcium orthophosphates
(Chapter 3), as well as by synthesis of calcium orthophosphates
with controlled particle geometry [537]. In general, the geometry
of crystal phases can be varied by controlling the precipitation
conditions, such as temperature, solution pH, concentration of
the reagents, hydrodynamics, presence of various admixtures,
inhibitors or promoters, ultrasonication, etc. All these approaches
might be useful in preparation of calcium orthophosphate fibers,
whiskers, hollow microspheres, etc. In addition, a great attention is
paid to manufacturing of the self-setting calcium orthophosphate
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