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Materials Science in Additive Manufacturing 3D-Printed hip joints performance

In addition to nanoparticle distribution, SEM images can results based on the ISO 7206-6 standard of the fabricated
also reveal the morphological characteristics of the TiO prosthesis are shown in Table 3. Three variations of
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nanoparticles. The nanoparticles may exhibit various composites were utilized to fabricate the prosthesis in the
shapes, such as spherical, rod-like, or irregular structures, study, namely polyurethane, polyurethane with 16 strands
depending on their synthesis method and properties. of glass fiber reinforcement, and a mixture of polyurethane
Observing the morphology of the nanoparticles provides and calcium carbonate with 16 strands of glass fiber
insights into their behavior and interaction within the reinforcement (PUCa16G). Of the three variations, the
resin matrix. PUCa16G variation results in the highest maximum load
of 1,739.73 N. In addition, the PUCa16G variation has a
The presence of lumps in SEM images of SLA resin 11
reinforced with TiO nanoparticles can be attributed modulus of elasticity similar to the human femur.
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to several factors, including the resin composition, Figure 15 shows the comparison of compression test
nanoparticle dispersion, processing conditions, and sample results between the study by Da Costa et al. and the
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preparation. One of the primary causes of lump formation present study. It can be seen that the strength of the artificial
is the agglomeration of nanoparticles. During the hip joint fabricated with TiO nanoparticle composite
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fabrication process, TiO nanoparticles may agglomerate is significantly lower than PUCa16G composite. This is
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due to interparticle forces such as van der Waals forces mainly due to the difference in the reinforcing materials
or electrostatic interactions, resulting in the formation used, where two reinforcing materials, calcium carbonate
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of larger clusters or lumps. Additionally, inadequate and glass fiber, were utilized by Da Costa et al. In addition,
dispersion of nanoparticles within the resin matrix can the maximum load of the artificial hip joint fabricated
also contribute to the formation of lumps. Therefore, a with TiO nanoparticle composite is also remarkably low
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homogeneous distribution of nanoparticles is crucial. compared to the one fabricated using PUCa16G composite,
Factors such as insufficient mixing, improper choice of as the strength of the dental photopolymer resin matrix is
dispersants, or high viscosity of the resin can restrict the weaker than the polyurethane matrix. The results of the
effective dispersion of nanoparticles. Moreover, the curing
or drying process of the SLA resin can also contribute to Table 3. Result from the study by Da Costa et al., based on
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the formation of lumps. As SLA resins undergo a curing ISO 7206‑6
or drying process to solidify the material, the resin may Materials Maximum load (N) Displacement (mm)
not solidify uniformly if the curing conditions, such as
temperature or curing time, are not properly controlled. PU 911.90±82.01 4.67±0.71
This non-uniform solidification can result in the formation PU16G 1043.84±132.57 8.34±1.56
of lumps or irregularities on the resin’s surface. Sample PUCa16G 1739.73±79.68 5.07±1.12
preparation for SEM analysis is another critical aspect Nanoparticle TiO 2 717.2 3.56
to consider. Improper sample preparation can introduce Abbreviations: PU: Polyurethane; PU16G: Polyurethane with
artifacts or contaminants that appear as lumps in the SEM 16 strands of glass fiber reinforcement; PUCa16G: A mixture of
images. For example, incomplete cleaning or inadequate polyurethane and calcium carbonate with 16 strands of glass fiber
drying of the sample can leave residues or moisture that reinforcement.
form irregularities or lumps in the images. To address the
issue of lump formation, several strategies can be employed.
Optimizing the dispersion process during resin formulation
or fabrication can help prevent agglomeration and ensure
a uniform distribution of nanoparticles. Controlling the
curing or drying conditions is also important in achieving
consistent solidification of the resin. Finally, proper sample
cleaning and drying techniques should be employed to
minimize the introduction of artifacts during the SEM
sample preparation.
3.4. Benchmarking

Da Costa et al. conducted a study on the fabrication of
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artificial hip joints using polyurethane reinforced with Figure 15. Comparison of the maximum load of the artificial hip joints
between Da Costa et al. and the present study
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glass fiber. The fabricated prosthesis has a modulus of Abbreviation: PUCa16G: A mixture of polyurethane and calcium
elasticity comparable to the human femur. The strength test carbonate with 16 strands of glass fiber reinforcement
Volume 4 Issue 3 (2025) 8 doi: 10.36922/MSAM025200032