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Materials Science in Additive Manufacturing MAM for orthopedic bone plates: An overview

two technologies: DED and PBF. Their market presence evolution, especially in terms of their constitutive
is substantial, with DED accounting for 16% and PBF a materials. Conventionally, these materials are grouped
dominant 54% of the 2020 market share . into metals, bioceramics, and polymers . Metals, due to
[31]
[52]
The DED and PBF techniques, as depicted in Table 1, their robust fixation capabilities and their resilience against
have distinct methodologies and parameters. DED stands daily mechanical loads, particularly in long bones, have
out for its adaptability, offering a range of feedstock become the primary choice for bone plates. For a detailed
options, including powders and wires. Moreover, its comparison of these metallic materials in orthopedic
versatility extends to energy sources, encompassing lasers, contexts, refer to Table 2.
electric arcs, and electron beams. This flexibility results Initially, vanadium steel was the preferred material for
in accelerated printing speeds, but often at the expense of orthopedic implants. However, its limitations, particularly
finer layer resolution. its subpar corrosion resistance and inadequate load-
PBF, in contrast, is distinguished by its precision. While bearing capacity, led to a search for better alternatives .
[17]
it primarily utilizes powders and has a more constrained This search culminated in the adoption of stainless steel
set of energy sources, it excels in delivering superior layer (316L SS) and titanium alloy (Ti-6Al-4V). Characterized
resolutions. A noteworthy advantage of PBF is its integral by improved corrosion resistance, mechanical strength,
powder bed. This not only provides the material base but also stiffness, and biocompatibility, these materials have since
serves as an intrinsic support structure. This dual functionality become staples in the orthopedic implant domain .
[53]
facilitates the creation of complex designs, eliminating the Furthermore, their versatility is evident in their
need for supplementary, and sometimes cumbersome, compatibility with modern AM techniques. Both can be
support structures. Such an attribute endows PBF with a processed as powder or wire feedstock, aligning well with
design adaptability that often surpasses that of DED . PBF and DED methodologies .
[51]
[54]
4. The comprehensive journey of AM-based While these materials have revolutionized orthopedic
bone plate production treatments, the biomechanics of bone healing introduces
new challenges. Mechanical stimulation and microinter
4.1. Selecting materials for orthopedic implants fragmentary motion play pivotal roles in optimal bone
Orthopedic implants play a crucial role in addressing bone regeneration. However, materials such as stainless steel
defects. Over the years, they have undergone significant and titanium alloy have a stiffness considerably surpassing

Table 1. Comparative analysis of key parameters for DED and PBF
Techniques General process Subcategory Feedstock Thermal Typical layer Deposition References
form energy type thickness (µm) rate (kg/h)
DED Metal powder or wire is consistently Laser additive Powders Laser 200 – 500 <0.50 [107,108]
introduced into the nozzle and subjected manufacturing
to a heat source (laser, electric arc or DED
electron beam). This results in the material
being melted to create a molten pool, Wire and Wires Electric arc 1000 – 2000 1.0 – 4.00 [107,109]
which conforms to the designated layer arc additive
configuration, and subsequently solidifies manufacturing
onto the substrate. This iterative process Wire and Wires Laser >1000 0.10 – 2.88 [107,109-111]
is reiterated to generate successive molten laser additive
pools layer upon layer until the printing manufacturing
procedure reaches its culmination
Wire and electron Wires Electron <3000 <19.80 [107,112]
beam additive beam
manufacturing
PBF A roller uniformly applies metallic powder Selective laser Powders Laser 25 – 75 0.10 – 0.30 [37,43,47,93,113]
onto a substrate, followed by controlled melting
melting using a laser or electron beam. Selective laser Powders Laser 80 – 500 0.10 – 0.20 [79,114]
Subsequent layers are added using the roller, sintering
leading to the gradual fabrication of the
product. This iterative process continues Electron beam Powders Electron 50 – 100 0.10 – 0.20 [7,35]
until the final desired structure is achieved melting beam
with integrity
DED: Directed energy deposition, PBF: Powder bed fusion

Volume 2 Issue 4 (2023) 5 https://doi.org/10.36922/msam.2113