Disinfection efficiency and its impact on the mechanical properties of multi-material mouthguards fabricated via fused filament fabrication

Mouthguards are orthodontic devices designed to prevent orofacial injuries during sports activities. To ensure comfort and correct positioning, they must fit the athlete’s dental arch precisely. Customization through additive manufacturing offers a practical solution for producing well-fitted mouthguards. The present study aimed to investigate the use of 3D-printed multi-material parts in the fabrication of protective mouthguards. Three polymeric materials were employed: High-impact polystyrene (HIPS), thermoplastic polyurethane, and poly(methyl methacrylate) (PMMA). Two configurations – bi-layered and tri-layered – were analyzed to assess the influence of material arrangement on mechanical performance. The impact of disinfection methods on mechanical properties was also evaluated, comparing physical (ultraviolet [UV]-C light exposure) and chemical (Polident cleaning tablet solution) disinfection strategies. In addition, the effects of artificial saliva aging on all material types and configurations were examined. Mechanical testing revealed that multi-material configurations containing HIPS exhibited superior mechanical performance, with flexural stiffness values 8 – 40% higher than PMMA-based samples, Vickers microhardness 40 – 128% greater, and absorbed energy and impact strength improved by 11 – 105%. Moreover, the tri-layered configuration demonstrated enhanced mechanical behavior, showing approximately 40% higher transverse impact resistance and increases of ~35% and ~77% in flexural strength and modulus, respectively, relative to the bi-layered configuration. Disinfection studies confirmed the efficacy of both approaches, reducing Staphylococcus aureus colony-forming units by 95% (Polident) and 97% (UVC light). These findings are promising for the development of protective mouthguards, where changes in mechanical properties over time – particularly due to saliva exposure and disinfection – are of critical importance.