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Kolan, et al.
glass and consequently, it degrades at a faster rate repair diverse regions of the skeletal system with
which allows quick release of calcium, boron, and different structural and biological requirements.
other ionic dissolution products and provides rapid The effect of scaffold architecture on
HA formation . Hence, in this study, biomimetic mechanical properties, cell proliferation, and bone
[7]
borate glass scaffolds for bone regeneration in rat regeneration has been investigated using polymer
calvarial defects were fabricated and characterized and metallic scaffolds [23-26] . There are inconclusive
in terms of material composition, porosity, reports on the influence of pore size on bone
architecture, and mechanical properties. regeneration. While some reports suggested pore
Among different additive manufacturing sizes in the range of 100 – 300 µm are beneficial
(AM) techniques, the powder bed fusion and for bone growth, other studies demonstrated
vat photopolymerization techniques enable increase bone tissue growth with pores >300 µm
the fabrication of complex lattice structures and up to 800 µm [27,28] . Some of these studies were
mimicking natural bone architectures, which performed using bioceramic scaffolds and others
is much more difficult to achieve with material were performed on biopolymer and metallic
extrusion techniques [8-10] . Thus, laser powder bed (titanium-based) scaffolds that do not degrade
fusion processes like selective laser sintering like bioactive glass. Bone repair using scaffolds
(SLS) can be used to create scaffolds with made from resorbable materials such as bioactive
different architectures to study the effects of pore glasses is likely to have distinct characteristics as
shape on the mechanical properties of scaffolds the scaffold properties change post-implantation
and their associated bone regenerative capacity. in the dynamic in vivo environment. For example,
Several methods were proposed to create scaffold silicate-based glasses degrade slowly even in
CAD models that possess a gradient of porosity, vivo because of the chemical stability of the SiO
conformity, and architectures that closely mimic network. A recent in vivo evaluation of silicate- 2
human trabecular bone [11-16] . Several challenges based glass scaffolds showed that about half of the
exist in the powder bed fusion-based 3D printing scaffold (unconverted glass) still remained in the
of ceramic/glass scaffolds with complex pores of defect region after 6 months . However, borate
[29]
size ranging from 100 to 600 µm because of the glass fibers used to treat a calvarial defect were
ceramic/glass material properties and sintering reported to degrade more quickly, with most of the
requirements . In the recent past, there has been glass converted to HA and resulting in better bone
[17]
interested in the fabrication of ceramic and glass regeneration in comparison to silicate glasses .
[30]
structures using the selective laser melting process The scaffold architecture could also play
with the help of high-temperature preheating of an important role in in vitro cell proliferation,
substrate [18-20] . Nevertheless, an indirect method differentiation, and bone regeneration, with
that involves additional post-processing after green some studies suggesting pore curvature driven
part fabrication allows for controlled structural tissue growth [24,31-33] . Although these in vitro
densification avoiding glass crystallization [21,22] . observations were, in general, in agreement with
Unlike metallic scaffolds, bioactive glass scaffolds theoretical predictions, the influence of curvature
degrade upon implantation in vivo or after soaking on tissue regeneration has not been demonstrated
in simulated body fluids (SBF), thereby affecting in vivo. Pore geometry, pore size, and porosity are
their structural integrity. Factors that influence interrelated. Importantly, the resorbable nature
this outcome include, but are not limited to, of borate glass could further complicate the
bioactive glass composition, scaffold porosity, mechanism of the bone regeneration process in
and pore geometry (which affects surface area for vivo, relative to more predictable bone formation
reaction). Therefore, investigating the effect of in metallic, or biopolymer scaffolds.
porosity and pore geometry on the degradation of In the present study, we hypothesized that a
scaffolds made with bioresorbable materials, such borate glass scaffold with biomimetic architecture
as bioactive glasses, could help design implants to would have sufficient strength and stiffness for

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