Biomedical Engineering Reference
In-Depth Information
quantity and promotion of the uniform mineral distribution in
that study was suggested to attribute to the perfusion effect [496].
Additionally, other investigators indicated to mechanical properties
increasing for other calcium orthophosphate scaffolds after induced
osteogenesis [495, 498].
Furthermore, the dimensions, extent and interconnectivity of
pores in bioceramics are known to influence bone ingrowth, blood
vessels formation and canaliculi networks [452, 453, 504]. Initial
reports have estimated a minimum pore size of ~50 μm for blood
vessel formation and a minimum pore size of ~200 μm for osteonal
ingrowth [504]. Pore dimensions of ~100 μm and even ~50 μm
[654] were reported in later studies to support bone ingrowth.
Additionally, vascularization, cell migration and nutrient diffusion
required for sustained cell viability and tissue function are possible
if pores within the scaffolds are well interconnected. For example, an
essential mean pore interconnection size of ~10 μm was found to be
necessary to allow cell migration between the pores [655]. As such,
both porosity and general architecture are critical in determining
the rate of fluid transport through porous bioceramics, which, in
turn, determines the rate and degree of bone ingrowth
in vivo
[115,
455, 456, 656].
4.7
Calcium Orthophosphate Bioceramics in
Tissue Engineering
4.7.1
Tissue Engineering
All modern orthopedic implants lack three of the most critical
abilities of living tissues: (i) self-repairing; (ii) maintaining of blood
supply; (iii) self-modifying their structure and properties in response
to external aspects such as a mechanical load [473]. Needless to
mention, that bones not only possess all of these properties but,
in addition, they are self-generating, hierarchical, multifunctional,
nonlinear, composite and biodegradable; therefore, the ideal artificial
bone grafts must possess similar properties [110].
The last decades have seen a surge in creative ideas and
technologies developed to tackle the problem of repairing or replacing
diseased and damaged tissues, leading to the emergence of a new
field in healthcare technology now referred to as
tissue engineering
.
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