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Noroozi, et al.:
are mainly stemmed from the difficulty of repeating the the traditional implant . To mimic the topology of natural
[44]
structure and function of the hosting bone . Researches tissues, three main grading can be considered, namely,
[10]
have strikingly progressed in the field of bone tissue variations in density, cell size, and the lattice type .
[46]
engineering during the last decades due to some advances Accordingly, several surface formulae, each of which
in the manufacturing process. defines a unique structure for the TPMS lattice, have
AM has introduced a novel way of production been introduced. Schoen-Gyroid, Schwarz-Diamond, and
from different perspectives. It has facilitated the Primitive are among the most famous TPMS structures.
manufacturing of complex geometries with the minimum Based on the scaffold’s specific mechanical behavior
waste material . The first efforts toward implementing and biological applications, a combination of these
[11]
AM-based production return back to the 1980s when structures, consisting of one or more lattice types, can
researchers used this method to create prototypes . be efficient in biomechanical terms [47,48] . Restrepo et al.
[12]
With the advent of other technologies, the true potential used three different 3D-printed ceramic patterns and
of this method got revealed [13-15] . Combining AM with evaluated their mechanical properties for bone tissue
computational methods, researchers can optimize the engineering . Liao et al. printed radial gradient TPMS
[49]
time, cost, and energy of production [16-20] . A compelling structures for bone tissue engineering and evaluated their
area of using three-dimensional (3D) printing is mechanical behavior under compressive test. In another
generating biomimicking organs or artificial tissues. For study, using the SLM printing method, multi-morphology
instance, the AM scaffold tissues can bear considerable scaffolds were printed, and their mechanical response
loads while they are efficiently lightweight [21-24] . was investigated by compression tests . In this vein, a
[50]
Mimicking the hosting cell heterogeneity is the main sound comprehension of the role played by transitional
advantage of creating artificial tissues using AM . zone (TZ) in multi-morphological scaffolds in terms of
[25]
Bone is a stiff tissue having heterogeneous morphology mechanical behavior is crucial for the development of
that can be replicated by printed lattice structures with suitable structures.
complex geometry. Therefore, fabricating novel porous Mimicking the hosting cell heterogeneity of bone
structures for bone tissue engineering, allowing patient- using lattice structures is the main advantage of creating
specific design, have been taken into consideration by artificial tissues using AM. A promising group of novel
researchers [26-28] . For example, Farina et al. 3D printed and lattice structures used in bone scaffolds is the so-called
evaluated a glass scaffold and provided a micro-computed TPMS structures which are function-based structures.
tomography (µCT)-based finite element modeling (FEM) TPMS structures can be readily produced using AM since
to investigate the mechanical properties of scaffolds . they are easily defined using mathematical equations, and
[29]
In another study, Askari et al. fabricated 3D zirconia a combination of different TPMS structures can satisfy
scaffolds for bone tissue engineering applications and mechanical and biological requirements . Therefore,
[51]
provided a µCT-based FEM for simulation . they are good candidates to design and manufacture
[30]
Designing bone scaffolds based on a mathematical scaffolds that can mimic bone’s heterogeneous nature.
algorithm, one of the latest design methods, has led However, different patterns joined together by a transition
researchers to use triply periodic minimal surface zone cell structure, cannot be arranged alongside one
(TPMS) structures [31-35] . The first TPMS surfaces were another without effects on the arising mechanical response;
initially described and introduced by Hermann Schwarz the adopted transition zone is particularly important in
in 1865 . TPMS-based bone scaffolds have some terms of mechanical properties. In this perspective, in
[36]
advantages, such as excellent nutrient transportation, this study, various multi-morphology scaffolds have been
oxygen diffusion, and ion exchange, making them a good printed by employing fused deposition modeling (FDM)
option for tissue engineering [37-39] . TPMS structures are printing method and using different cell types, including
geometrically complex so that it is somehow impossible gyroid, diamond, and I-graph and wrapped package graph
to produce such precise geometries with standard (I-WP).
manufacturing processes. However, using AM, these Literature review shows that researchers have
fascinating structures can be effortlessly produced. TPMS not adequately considered the comprehensive study of
structures are novel mathematical geometries that can multi-morphology scaffolds. Furthermore, in this study,
be utilized in several areas, including heat exchangers, the mechanical properties of printed multi-morphology
body implants, and lightweight structures [40-45] . Their scaffolds with different TZ under compression tests have
applications in bioengineering have provided researchers been evaluated, and FEM analyses have been used to
with novel solutions to prevailing problems in creating validate experimental results. Since the elastic response
biomimicking tissues and organs. For example, Song of scaffolds under mechanical loads is the fundamental
et al. designed and analyzed the route analog dental aspect to be considered in biomechanical applications,
implant based on TPMS structures and compared it with the behavior of printed scaffolds within the linear

International Journal of Bioprinting (2022)–Volume 8, Issue 3 41