Biomedical Engineering Reference
In-Depth Information
twentieth century. Moreover, calcium orthophosphate cements can
be injected directly into the fractures and bone defects, where they
intimately adapt to the bone cavity regardless its shape. More to the
point, they were found to promote development of osteoconductive
pathways, possess sufficient compressive strengths, be non-cytotoxic,
create chemical bonds to the host bones, restore contour, and have
both the chemical composition and X-ray diffraction patterns
similar to those of bone [28]. Finally but yet importantly, they are
osteotransductive, i.e., after implantation, calcium orthophosphate
cements are replaced by a new bone tissue [29-31].
The aim of biomimetic bone cements is to disturb bone
functions and properties as little as possible and, until a new bone
has been grown, to behave temporary in a manner similar to that
of bone. From a biological point of view, this term defines cements
that can reproduce the composition, structure, morphology, and
crystallinity of bone crystals [32, 33]. Therefore, the discovery of
self-setting calcium orthophosphate formulations was a significant
step forward in the field of bioceramics for bone regeneration,
since it established good prospects for minimally invasive surgical
techniques that were less aggressive than the classical surgical
methods [34]. Such formulations provide surgeons with a unique
ability of manufacturing, shaping, and implanting the bioactive bone-
substitute materials on a patient-specific base in real time in the
surgery room. Implanted bone tissues also take benefits from initial
setting characteristics of the cements that give, in an acceptable
clinical time, a suitable mechanical strength for a shorter tissue
functional recovery. The major advantages of the self-setting calcium
orthophosphate formulations include a fast setting time, excellent
moldability, outstanding biocompatibility, and easy manipulation;
therefore, they are more versatile in handling characteristics than
prefabricated calcium orthophosphate granules or blocks. Besides,
like any other type of calcium orthophosphate bioceramics, the self-
setting formulations provide with the opportunity for bone grafting
using alloplastic materials, which are unlimited in quantity and
provide no risk of infectious diseases [35-37].
Since self-setting calcium orthophosphate formulations are
intended for using as implanted biomaterials for parenteral
application, for their chemical composition one might employ all
ionic compounds of oligoelements occurring naturally in a human
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