Biomedical Engineering Reference
In-Depth Information
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Figure 9.2 A selection of PCL-based scaffolds fabricated using AM techniques. (a) A
customised PCL scaffold used for mandibular defect reconstructions.
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(b) An Osteoplug
t
implant designed to cover burr-hole skull defects.
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(c) A bobbin-shaped scaffold to maximise empty space and increase
vascularisation.
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(d) A scaffolds with incorporated vascular channels
(indicated in red) in an arborising pattern following an open channel
design.
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(e) A customised scaffold used to repair a segmental defect in a
long bone.
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.
In 2002, Zein et al.
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explored the effects of different fabrication par-
ameters for FDM PCL porous scaffolds and how these affect porosity and, in
turn, mechanical strength. Different raster angles (0/901 and 0/60/1201) and
FG lengths (0.508, 0.610 or 0.711 mm) were explored along with two different
nozzle tip sizes (254 or 406 mm).
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All fabricated scaffolds exhibited a regular
honeycomb-like pattern and fully interconnected pore channels. As would be
expected, smaller tip sizes produced scaffolds with larger channel diameters
[as long as the FG (Figure 9.1c) was kept constant]. This decrease in tip size
increased porosity from 48-61% to 71-77%.
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It was observed, however, that
with smaller tip sizes, de-lamination was more likely to occur between layers.
The fabricated scaffolds were mechanically tested and it was observed that
increased porosity led to decreased compressive strength, yield strength and
yield strain, regardless of lay-down pattern, FG and RW. This inverse rela-
tionship between porosity and scaffold mechanical strength means that
there will likely be a compromise when fabricating a scaffold for bone tissue
engineering applications. This is because the scaffold obviously needs to be
strong but it also requires suitable porosity for tissue in growth and inte-
gration. The porosity allows the movement of cells through the scaffold as
well as the diffusion of nutrients/waste. Ideally, this porous structure will
support and assist vascular
integration into the scaffold. A similar
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