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3D Printing Technologies in Metallic Implants
producing complex shapes, and difficulty to manufacture
the custom-built designs. Hence, advance procedures are
highly required to meet various demands from patients
and healthcare market.
Three-dimensional printing (3DP) is an evolutionary
technology and a branch of additive manufacturing
(AM) methods that cover a range of applications in
modern industries, including manufacturing of computer
components, electricity, machinery, and digital control
devices . According to the AM principles and the use of
[2]
special 3D bioprinters, human organs can be artificially
produced in the future, and the realization of this goal
[3]
will be accompanied by a revolution in the healthcare
system. These 3DP techniques have great potentials
in producing porous and complex-shaped materials
and components with very intricate internal structures.
Therefore, 3DP technology enables fabrication of
hierarchical materials with porous structure and
mechanical properties (strength and elastic Young’s
modulus) very similar to natural bone and inhibits
stress-shield effect in bone implants [4-6] . Moreover, 3DP
technologies have some other advantages, including
the ability in mass production, economic efficiency,
low cost, repeatability, and shorter time to market .
[2]
In addition, 3D technology together with computer-
aided design (CAD) technique can be used in the
[7]
production of completely patient-specific implants [8,9] .
3DP method developed rapidly and a variety of new
techniques with many advantages were devised to cure
the previous limitations. The first description about 3DP
dates back to 1981 when Dr. Hideo Kodama fabricated
a device that uses ultraviolet (UV) lights to harden
polymers and create solid objects [10] . Although it was not
commercialized, it was the first step to the conception
of stereolithography (SLA) technique in 1983. Later,
Charles Hull invented the first SLA machine . In 1987,
[11]
a selective laser sintering (SLS) process was patented,
and the first commercial rapid prototyping printer
entitled SLA-1 was sold 1 year later. Subsequently,
fused deposition modeling (FDM) and laser AM (LAM)
were introduced. Following the introduction of newly
developed 3D printing techniques, Israeli scientists
made a successful achievement in the fabrication of
an entire heart with human cells in 2019 [12] , Figure 1
schematically represents the 3DP history.
The 3DP process is performed sequentially based on
the following steps: First, using the digital design software
(SolidWorks, AutoCAD, Autodesk, etc.), 3D digital
scanners, or other applications, the digital virtual version of
the desired object is generated. Then, the 3D digital model
is transformed into SLA or standard tessellation language Figure 1. Timeline of 3D printing technologies.
(.STL) file format. The .STL file involves numerous
triangulated facets that demonstrate the exact spatial number of triangles means more data points and higher
coordinates (xyz) information of 3D model surfaces. A large resolutions. Third, by utilizing particular slicer software in

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