Biomedical Engineering Reference
In-Depth Information
resorption rate has to coincide as much as possible with the rate
of bone formation (i.e., between a few months and about 2 years)
[686]. This means that while cells are fabricating their own natural
matrix structure around themselves, the scaffold is able to provide a
structural integrity within the body and eventually it will break down
leaving the newly formed tissue that will take over the mechanical
load. Besides, scaffolds should be easily fabricated into a variety of
shapes and sizes [687] and be malleable to fit irregularly shaped
defects. In many cases, ease of processability, such as an easiness
of conformation, and injectability, such as self-setting calcium
orthophosphate formulations possess (Chapter 5), can determine the
choice of a certain biomaterial. Finally, sterilization with no loss of
properties is a crucial step in scaffold production at both a laboratory
and an industrial level [665]. In conclusion, since ions of calcium and
orthophosphate are known to regulate bone metabolism, calcium
orthophosphates appear to be among the few bone graft substitute
materials, which can be considered as a drug [2].
Table 4.5
A hierarchical pore size distribution that an ideal scaffold
should exhibit [12]
Pore sizes of a 3D scaffold A biochemical effect or function
Interaction with proteins
< 1 μm
Responsible for bioactivity
Type of cells attracted
Cellular development
1-20 μm
Orientation and directionality of cellular
ingrowth
Cellular growth
Bone ingrowth
100-1000 μm
Predominant function in the mechanical
strength
Implant functionality
>1000 μm
Implant shape
Implant esthetics
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