# Ergonomic Sports Mouthguards: A Narrative Literature Review and Future Perspectives
## 3 Discussion
Given the biomechanical behavior of the different types of mouthguards available, the use of ergonomic custom-made devices is recommended for sports that involve high speeds, heights, and physical contact, as well as other sports that can cause orofacial trauma during practice, for both amateur and high-performance athletes, since the stock (pre-fabricated) and mouth-formed (boil and bite) devices do not meet the requirements to guarantee adequate retention [26]. The suggested thickness for creating EVA mouthguards to ensure effective impact absorption capability ranges between three to four millimeters [14]. [PERSON] and colleagues (2002) found that increasing the thickness beyond 4 mm resulted in only a minor enhancement in impact absorption. However, this slight improvement would not offer significant benefits and could potentially compromise user comfort, thereby potentially discouraging the usage of the device [2]. The incorporation of reinforcements into EVA mouthguards reveals significant improvements in the mechanical performance of these devices, such as enhanced impact absorption compared to conventional mouthguards. Various forms of reinforcements have been studied, and their effectiveness has been proven through in vitro studies. These forms include the inclusion of an air cavity in 4 mm of EVA [12; 48], the addition of an intermediate layer of Sorbothane as reinforcement, reducing the transmission of impact to adjacent structures by approximately 30% [36], the insertion of a sponge between two layers of EVA [12], and the utilization of a silicone intermediate layer [38]. While these studies present favorable outcomes for reinforcement incorporation, it is important to note that the methodologies employed in these studies have limitations in terms of applied load, with lower impact magnitude compared to real-life situations faced by athletes. It is essential to acknowledge the difficulty in standardizing load application in vitro studies, but it is worth developing methodologies that involve more realistic tests and analyses aimed at understanding the behavior of adjacent structures when subjected to impacts using different types of mouthguards [48]. Additionally, a combination of two methodologies, such as in vitro and in silico, could provide validation for the studied methodologies [49; 50]. Athletes consider two factors when choosing intraoral protection devices: the cost and the time required for acquisition. Stock mouthguards are the most cost-effective, followed by 'boil-and-bite' mouthguards, which are readily available in sports stores and pharmacies, allowing athletes to make their own choices based on what they believe is suitable. Despite the issues associated with these types, such as lower protection rates compared to custom-made mouthguards, they offer quick acquisition without the need for multiple appointments. In contrast, custom-made mouthguards require several appointments that include impression taking, device adjustment appointments, and follow-ups. While this individualized approach is advantageous in terms of protection, some patients view its drawbacks of higher time and cost as not worth the trade-off. However, addressing this concern through educational efforts, emphasizing differences in protection levels and potential trauma-related issues can encourage athletes to choose custom-made mouthguards. Regarding the potential for the use of additive manufacturing in mouthguard fabrications, mouthguards using Agilus30 resin did not show superior performance when compared to conventional EVA mouthguards under free-fall weight impact tests. However, conventional mouthguards exhibited surface imperfections such as the presence of microbubbles and variations in thickness [42]. In contrast, the 3D-printed mouthguards displayed surface uniformity as well as consistent thickness, suggesting the need for further research analyzing different polymer types to establish a comprehensive recommendation for the adoption of printed materials as a substitute for conventional EVA mouthguards.