Abstract
Three-dimensional (3D) scaffolds with tailored pores ranging from
the nanometer to millimeter scale can support the reconstruction
of centimeter-sized osseous defects. Three-dimensional-printing processes
permit the voxel-wise fabrication of scaffolds. The present study
rests upon 3D-printing with nano-porous hydroxyapatite granulates.
The cylindrical design refers to a hollow bone with higher density
at the periphery. The millimeter-wide central channel follows the
symmetry axis and connects the perpendicularly arranged micro-pores.
Synchrotron radiation-based micro computed tomography has served
for the non-destructive characterization of the scaffolds. The 3D
data treatment is essential, since, for example, the two-dimensional
distance maps overestimate the mean distances to the material by
33-50\% with respect to the 3D analysis. The scaffolds contain 70\%
micrometer-wide pores that are interconnected. Using virtual spheres,
which might be related to the cells migrating along the pores, the
central channel remains accessible through the micro-pores for spheres
with a diameter of up to (350+/-35)mum. Registering the tomograms
with their 3D-printing matrices has yielded the almost isotropic
shrinking of (27+/-2)\% owing to the sintering process. This registration
also allows comparing the design and tomographic data in a quantitative
manner to extract the quality of the fabricated scaffolds. Histological
analysis of the scaffolds seeded with osteogenic-stimulated progenitor
cells has confirmed the suitability of the 3D-printed scaffolds for
potential clinical applications.
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