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Materials Science in Additive Manufacturing Mouthguards: Disinfection versus properties changes

particularly associated with severe dental fractures and These manufacturing strategies typically use 4 mm-thick
soft tissue traumas, which may lead to more serious sheets of the copolymer poly(ethylene-vinyl acetate) (EVA),
1
complications, such as mandibular fractures and facial which are heated and molded over a cast of the athlete’s
bone fractures, even irreversible brain damage. 2,3 dentition. EVA is favored for its impact resistance and
6,14
Since 1960, the American Dental Association (ADA) favorable mechanical and physical properties. However,
has recommended the use of mouthguards across a range of its relatively low rigidity and hardness limit its energy
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sports to reduce the incidence of such injuries. According dissipation capacity. Moreover, EVA is prone to swelling,
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to the American Society for Testing and Materials (ASTM), which can lead to dimensional and geometrical instability,
a mouthguard is defined as a “sturdy device or appliance including increased thickness. In addition, issues related to
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placed inside the mouth to reduce oral injuries, particularly microbial adhesion have been reported.
to the teeth and surrounding structures.” An effective Conventional manufacturing techniques also involve
5
mouthguard should fit the athlete’s dental arch precisely, multiple production stages and generate considerable
cause minimal discomfort, and provide protection against material waste, raising concerns about the environmental
impact-related injuries to the teeth and surrounding tissues sustainability of mouthguard fabrication. To address these
during contact sports. 6,7 limitations, additive manufacturing has been investigated
as an alternative production method. 6,11,17 In particular,
Following ADA guidelines, mouthguards are classified
into three categories: Extraoral, intraoral, and combined fused filament fabrication (FFF) is considered a more
sustainable approach, as it eliminates the need for molds
types. Intraoral mouthguards are further subclassified 6
8
based on their manufacturing method into three categories: and minimizes material waste. As such, FFF presents a
Stock, “boil and bite,” and custom-made mouthguards. 8 viable strategy for producing protective mouthguards that
are more closely tailored to the athlete’s dental arch.
Stock protective devices (type I) are commercially
Nonetheless, several challenges hinder the application
available in standardized sizes at affordable prices. of FFF in dentistry, including fiber orientation, weak
However, their inability to conform to the athlete’s oral interfacial bonding between the fiber and matrix, and
anatomy compromises their functionality, reducing their void formation. Multi-material 3D printing, however,
ability to absorb and dissipate impact energy effectively. offers a promising solution by integrating materials
These devices may also create a false sense of security and with distinct mechanical and physical properties. This
are often associated with discomfort, including nausea and approach enhances the overall mechanical performance
respiratory difficulty. 6,9
of printed components and enables the introduction of
“Boil and bite” mouthguards (type II) are an improved novel functionalities. In the context of mouthguard
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version of type I mouthguards. Made from thermoplastic development, it soon became evident that the standard
polymers, they can be softened in hot water and molded 4 mm thickness of commercially available devices posed
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to the user’s teeth and oral tissues. While they offer better a major obstacle for athletes. Reducing the thickness of
6
adaptation than stock mouthguards, they do not provide these devices emerged as a critical design goal. However,
a fully customized fit and may still cause discomfort, this seemingly straightforward objective could not be
11
as well as difficulty breathing or speaking during use. achieved using monolithic materials such as EVA, which
With repeated use, there is a significant risk of dental is currently the material of choice for conventional
damage, particularly to the most prominent teeth, due mouthguards. This limitation underpins the rationale for
to the progressive reduction in thickness from wear. This adopting a multi-material approach. By combining rigid
degradation compromises the device’s ability to provide and soft materials – offering mechanical strength and
effective orofacial protection. 6,9,12 impact energy absorption, respectively – this strategy
Custom-made mouthguards (type III) are fabricated has been shown to improve protective performance, as
to offer superior fit and alignment with the athlete’s dental demonstrated in previous studies. 18,19
arch, thereby enhancing intraoral stability and minimizing In addition to mechanical performance, the correct
the risk of dislodgment and mechanical failure. However, disinfection of mouthguards is crucial for safeguarding
9
these devices must be custom-manufactured and require athletes’ health. Due to the high microbial load of the oral
at least one dental consultation, resulting in a significantly cavity, it is essential to disinfect these devices after each
higher cost compared to types I and II. 6,9,12 use to minimize contamination risk and prevent illness,
Currently, most custom-made mouthguards are similar to hygiene protocols in clinical settings. 20,21
produced using thermoforming technologies, encompassing Despite the favorable results related to mouthguard
both pressure and vacuum thermoforming methods. hygiene, standardized guidelines for optimal disinfection
6,13

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