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Materials Science in Additive Manufacturing Hydrogels in mandibular reconstruction

through innovative incorporation of high-concentration extrusion printing (Figure 6B-D). These three printing
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β-tricalcium phosphate (β-TCP). Their research revealed techniques can also effectively print hydrogels of desired
that positive charges on β-TCP particles form dense shapes or structures using other mixed materials,
electrostatic networks with negative charge groups in including cells, growth factors, and more. A variety of
the chitosan/collagen matrix, significantly enhancing hydrogel materials – such as gelatin, collagen, alginate,
interpolymer chain cohesion and delaying hydrogel and PEG diacrylate – are commonly utilized in the
swelling/degradation. development of laser-assisted 3D-printed scaffolds. 69,70

Hydrogel degradation characteristics directly This printing technology allows for the precise production
determine bone regeneration efficiency. Given the of complex 3D structures based on computer-aided design
accelerated remodeling of mandible, hydrogels require and computer-aided manufacturing models, printing the
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faster degradation rates to accommodate osteogenesis desired hydrogel scaffolds with micrometer-level resolution
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needs. Excessive degradation risks premature scaffold while effectively avoiding damage to the cells. Gruene
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collapse and loss of structural support, while insufficient et al. used alginate hydrogel-coated donor strips for the
laser printing of mesenchymal stem cells and confirmed
degradation impedes bone ingrowth and delays healing.
Ideal degradable hydrogels achieve precise degradation that the laser printing technology can effectively reduce
rate control through optimized crosslinking density, cell damage during the printing process, which is crucial
natural/synthetic polymer composites, or responsiveness for cell viability and subsequent tissue regeneration. The
to external stimuli (enzymatic action, pH), thereby printed bone grafts demonstrated good osteogenic and
chondrogenic differentiation in vivo, which proves the
creating spatial accommodation for new bone formation
during degradation. effectiveness of this technology in bone and cartilage tissue
engineering. Inkjet printing technology can precisely
3.3. Three-dimensional bioprinted hydrogels construct customized bone repair implants by layer-by-
layer deposition of biomaterials. This technology is suitable
The optimal scaffold mimics the structural and biochemical for both on-demand and continuous jetting systems, where
properties of natural bone, delivering nutrients to grafted liquid biomaterials are jetted layer by layer onto a substrate
cells, releasing bioactive signaling molecules, and allowing for 3D-printing hydrogel-based scaffolds. Inkjet-based
for vascularized tubular structures. These advantages can printing methods offer excellent precision and resolution
positively impact the success of bone grafts. However, (50 – 500 µm) for manufacturing complex 3D structures.
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constructing a vascularized structure that simulates In thermosensitive inkjet printers, acrylated PEG can
natural tissue remains a major challenge. Thus, advanced be combined with acrylated peptides or GelMA,
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micropatterning methods – such as 3D printing – have enabling the fabrication of hydrogel-based scaffolds
emerged, enabling the design of 3D frameworks that boost through in situ photopolymerization during the printing
blood vessel formation while maintaining optimal porosity procedure. Human mesenchymal stem cells (hMSCs) have
to support cellular integration and growth. 66,67 Through 3D been encapsulated within these hydrogels and directly
bioprinting technology, it is possible to precisely construct printed alongside them, resulting in enhanced capabilities
hydrogel scaffolds that match the anatomical structure of for osteogenic (bone-forming) and chondrogenic
a patient’s mandible. These scaffolds can be loaded with (cartilage-forming) differentiation. Extrusion-driven 3D
osteogenic cells and growth factors, providing an ideal bioprinting is commonly employed in tissue engineering
microenvironment for bone tissue regeneration (Figure 6A). and regenerative medicine due to its adaptability with
When these 3D-bioprinted hydrogel scaffolds are implanted diverse biomaterials and crosslinking approaches. This
into mandibular defect sites, they can promote the technology is particularly suitable for shear-thinning
regeneration and vascularization of bone tissue, effectively materials, such as alginate, PEG-based hybrid hydrogels,
restoring the structure and function of the mandible. The and GelMA hybrids. 75,76 In bone and cartilage tissue
porous structure and high water content of the hydrogel engineering, alginate, polycaprolactone, and GelMA are
facilitate the exchange of nutrients and waste, further the main materials for extrusion bioprinting. Extrusion
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promoting cell growth and differentiation. In addition, bioprinting is regarded as viable for fabricating hydrogels
3D bioprinting technology allows for the personalized that incorporate alginate or Lutrol F127 (a poly(ethylene
customization of hydrogel scaffolds tailored to the specific oxide)-poly(propylene oxide) copolymer) alongside
mandibular defect of each patient, based on their facial BMSCs, maintaining compatibility and functionality in
anatomical data, thereby achieving personalized treatment.
bioprinting applications. Cells printed through extrusion
3D printing technologies used for various hydrogel bioprinting not only remain viable throughout the process
applications include laser printing, inkjet printing, and but also express osteogenic markers such as alkaline

Volume 4 Issue 2 (2025) 11 doi: 10.36922/MSAM025070006