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Materials Science in Additive Manufacturing Mouthguards: Disinfection versus properties changes

practices and appropriate disinfection agents are still supported the inclusion of the three polymers evaluated in
lacking. 22,23 Furthermore, few studies have investigated how this study. Additionally, 4 mm-thick bulk EVA specimens
disinfection strategies affect the mechanical performance were acquired from Dentaflux (Spain) to compare the
of mouthguards. Existing disinfection and sterilization mechanical properties of conventional mouthguard
methods include ultrasonic cleaning and the use of materials with those fabricated via 3D printing.
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commercially available cleaning tablets, such as Corega, Thermoplastic polyurethanes are good shock absorbers
Fittydent, and Polident. 22,23 and easy to process, making them promising candidates
Therefore, the present work aimed to develop multi- for mouthguard manufacturing and potential substitutes
material mouthguards using FFF technology, incorporating for EVA. However, the issue of excessive mouthguard
thermoplastic polyurethane (TPU) as the soft material thickness remains unsolved, as both TPU and EVA are
and high-impact polystyrene (HIPS) and poly(methyl elastomeric polymers with relatively low impact strength.
methacrylate) (PMMA) as rigid materials. Two material To address this limitation, a multi-material strategy was
configurations were assessed, namely a sandwich-like employed, combining impact-resistant materials such as
tri-layered configuration and a bi-layered configuration. PMMA or HIPS with TPU to reduce the overall device
The choice of materials was based on previous research. thickness. Both PMMA and HIPS are widely available,
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Mechanical performance was assessed through three- cost-effective, and easily processed through FFF. 25,26
point bending tests and transverse impact tests to evaluate Table 1 summarizes the properties and selected biomedical
flexural and impact resistance, respectively. A novel aspect applications of HIPS, TPU, and PMMA.
of the current work is the investigation of the effects of To simulate an intraoral environment, all specimens
artificial saliva aging and disinfection procedures – both were soaked in artificial saliva prepared following the
physical (ultraviolet [UV]-C light) and chemical (cleaning Fusayama–Meyer formulation (Table 2), in compliance
tablet solution) – on the mechanical properties of the with ISO 10271. Potassium chloride, sodium chloride,
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multi-material mouthguards. calcium chloride dihydrate, monosodium phosphate, and
urea were obtained from Panreac (Spain), whereas sodium
2. Materials and methods sulfate monohydrate was purchased from Sigma-Aldrich

2.1. Materials (Germany).
The present study examined three commercially available 2.2. Chemical characterization of the filaments
polymeric filaments (Ø = 1.75 ± 0.04 mm), used without Fourier transform infrared (FTIR) spectroscopy was used
further modifications: PMMA, purchased from TreeD to validate the chemical composition of the filaments
Filaments (Italy); TPU, commercially labeled as Traffic and to detect any potential chemical modifications
Black, acquired from BeeVeryCreative (Portugal); and following disinfection procedures. The analysis was
HIPS, supplied by DoWire (Portugal). As previously conducted using a Bruker Alpha II spectrometer
stated, the selection of these materials was based on (mid-infrared: 4000 – 400 cm ; Bruker, United States),
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previous studies conducted by the authors, particularly equipped with an RTDLATGS detector (Bruker, United
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considering their performance in energy absorption and States) and a KBr beam splitter (Bruker, United States).
dissipation during impact testing. These characteristics Spectra were recorded at room temperature with a

Table 1. Properties and biomedical applications of HIPS, TPU, and PMMA
Material Properties and characteristics Biomedical applications References
High-impact Dimensional stability, compatibility with radiation Catheter trays, heart pump trays, epidural trays, 27,28
polystyrene (HIPS) sterilization, high impact strength. More ductile than respiratory care equipment, syringe hubs, suction
polystyrene due to the addition of an elastomer to canisters, and bone replacements.
the polymer backbone, while maintaining equivalent
cytocompatibility.
Thermoplastic Combines flexibility (soft segments) and stiffness (hard Blood bags, heart valves, vascular grafts, long- and 29,30
polyurethane (TPU) segments); chemical stability; good lubricity and abrasion short-term implants, and cardiac pumps.
resistance; elastomeric behavior; high shock absorption
capacity.
Poly (methyl Good optical properties; long-term mechanical stability; Bone cement, intraocular lenses, artificial corneal 31,32
methacrylate) high impact strength; lightweight; shatter-, weather-, and implants (keratoprosthesis), bone substitutes, and
(PMMA) scratch-resistant. mandibular reconstruction.

Volume 4 Issue 2 (2025) 3 doi: 10.36922/MSAM025130018