Page 135 - MSAM-4-2

Materials Science in Additive Manufacturing Mouthguards: Disinfection versus properties changes

Table 4. Roughness parameters of the printed samples
Material Configuration Treatment r factor (µm) Sa (µm) Sq (µm)
HIPS Bi-layered configuration Dry 6.0±0.7 27.7±2.7 35.5±2.9
Pre-disinfected 4.5±2.3 27.5±5.9 35.0±6.5
Post-UVC 4.8±1.2 28.5±9.5 35.4±10.4
Post-Polident 5.0±1.2 31.8±6.1 37.7±6.2
Tri-layered configuration Dry 3.7±0.8 26.4±6.9 32.3±9.0
Pre-disinfected 2.7±0.3 20.4±2.6 25.0±3.0
Post-UVC 2.0±0.4 14.6±6.6 18.6±8.0
Post-Polident 2.9±0.8 24.0±2.2 29.3±2.7
PMMA Bi-layered configuration Dry 4.1±0.4 22.8±4.9 28.8±5.4
Pre-disinfected 3.9±0.6 27.5±2.6 33.2±3.3
Post-UVC 3.3±1.4 19.7±5.0 25.8±5.6
Post-Polident 3.9±0.8 24.5±3.4 30.1±3.1
Tri-layered configuration Dry 1.8±0.4 19.5±7.3 26.0±10.0
Pre-disinfected 2.0±0.6 21.4±6.7 27.3±7.8
Post-UVC 2.9±0.8 19.9±4.4 24.5±5.5
Post-Polident 2.6±0.5 26.7±3.2 31.3±3.9
Abbreviations: HIPS: High-impact polystyrene; PMMA: Poly (methyl methacrylate).

All tested configurations exhibited hydrophobic behavior, 4. Conclusion
consistent with prior findings. The wettability of the
11
materials is an important parameter, as saliva accumulation on The main goal of this study was to investigate the
the mouthguard surface can promote bacterial proliferation mechanical properties of two multi-material configurations
within the device. For applications involving contact with for the fabrication of customized mouthguards using
17
tissues or cells, a material is considered hydrophilic when the additive manufacturing, particularly via FFF technology.
contact angle with a water droplet is <65°. 55 More specifically, the study evaluated the effects of two
disinfection methodologies – physical (UVC) and chemical
A comparison between the tested materials revealed (Polident solution) – on mechanical properties.
that HIPS surfaces exhibited a slightly more hydrophobic
character than PMMA, although the differences were not The results demonstrated that the disinfection process
statistically significant. significantly influenced the mechanical properties of the
printed components, as evidenced by three-point bending
As expected, specimens in the dry state demonstrated and microhardness tests.
a more pronounced hydrophobic character – indicated by
higher θ values – for both materials and configurations. Characterization demonstrated that HIPS exhibited
r
This may be attributed to the sorption of ionic compounds higher values of flexural modulus, absorbed energy,
following immersion in artificial saliva, which increases and impact strength, whereas PMMA displayed greater
surface cohesion and improves wettability, thereby flexural strength. Among the configurations tested, the
reducing resistance to wetting. 17,55 tri-layered structure emerged as the optimal option for
protective mouthguard fabrication, owing to its reduced
Overall, specimens disinfected with UVC exhibited a susceptibility to damage and superior mechanical
lower degree of hydrophobicity compared to those treated properties, including higher values of ,, absorbed energy,
with Polident. UV radiation likely induces chemical bond and impact strength.
disruption and surface degradation, 52,56 which in turn alters
surface roughness parameters and facilitates the spreading Notably, the findings also indicate that the thickness of
of water droplets. Nevertheless, despite this reduction in the mouthguard can be reduced while still improving its
hydrophobicity, the corrected contact angle remains above mechanical properties compared to 4 mm-thick bulk EVA.
65°, indicating that the UVC disinfection method does This reduction in thickness can diminish the discomfort
not significantly contribute to saliva accumulation on the experienced by athletes during use, while still ensuring
mouthguard surface. 11,55 effective impact protection.

Volume 4 Issue 2 (2025) 12 doi: 10.36922/MSAM025130018