Page 35 - IJB-7-1

Attarilar, et al.
Table 1. (Continued)
Technique Pros Cons References
Direct ink writing • Easy to use with hydrogels • It is not a good choice for complex [76,77]
(DIW) • Simple nature parts and processes
• Possibility to use multiple inks • Crucial to carefully control the
• Cost-effectiveness thickening and thinning agents in
• Environmental friendliness bio-ink
• Hard to attain the desired
microstructure
• Hard to extrude liquids
Fused deposition • Lower toxicity compared to 3D printing • Need to use additional support [78]
modeling (FDM) with photopolymers structure
• Cheap procedure • Need to do post-processing
• Low resolution
Bioplotting • Possibility to print viable cells • Limited size ranges for nozzle [74]
• Suitable for soft tissue • Need to use additional support
structure
Laser-assisted • Excellent precision printing • Expensive [74,77]
bioprinting (LAB) • Single-cell patterns • Scaffolds have limited heights
• It can use various bioactive materials
• It can print different solutions at a time
• Easy automation
• High throughput

with materials without any pores. This parameter can ends due to isolated pore structures impede the growth
be influenced by pore size, strut thickness, and pore of the cells and cause poor cellular interactions, such as
shape. It is believed that higher porosities lead to better differentiation, osteogenesis, and angiogenesis. Higher
growth of osteon cells, increase the surface area which values of the influencing factors, such as detour indexes
causes more cellular interactions, and provide proper and pore throats, can sometimes lead to suppression of
interface-locking in laser-processed porous titanium . the proper bone ingrowth and tissue formation .
[89]
[94]
Moreover, it has been shown that pore shape can affect It is difficult to obtain the desired pore size and
osteogenic differentiation . The improved osteogenic shape, porosity, and interconnection at the microscale
[90]
differentiation was observed on scaffolds with high level with traditional ways and evaluate their possible
porosities compared to low-density ones . In fact, the biological effects. However, it is rather simple to obtain
[91]
porosity of human trabecular bone is within in the range well-designed and regular pore structures through AM
of 70 – 90%, so this range seems to be suitable for a 3D technology. The CAD-based models can be utilized to
printed implant. In a previous study by Cheng et al., predesign and produce any kind of porous structure using
different porosities (70%, 37.9%, and 15%) were designed 3DP technologies. Two porous structures can be used: The
in EBM-produced Ti6Al4V samples, and the sample with honeycomb-like structure is a CAD-based structure with
the highest porosity has a higher potential for stimulating a diamond lattice, in which each atom is enveloped by
osteoblast differentiation than the other samples . Other four neighboring atoms [95,96] , while the cubic structure is
[92]
studies also confirmed this observation and asserted that formed by scanning powder layers with the use of electron
implants with porosities similar to human bone’s (70 – beams in constant intervals and parallel manner, and in
90%) had the best bone ingrowth and greatly improved every eighth layer, the scanning direction is rotated 90° .
[97]
cell viability, but there would be some differences about
the results of other biological responses toward porosity, (4) Lattice structure topologies
like cell proliferation and differentiation [87,93] . Many studies have focused on improving the lattice
designs, especially on from the aspects of weight
(3) Interconnectivity of pores
reduction and customizability, and various lattice
The interconnectivity of pores determines whether the structure topologies have therefore been proposed. In
pores are connected or isolated. Formation of tissues in the this regard, truss lattices with interconnecting struts in a
interconnective structures can be progressively continued 3D space are among the well-known class of lightweight
from the openings up to the central regions while dead parts. They have superior strength, stiffness, and energy

International Journal of Bioprinting (2021)–Volume 7, Issue 7 31