Influence of different ethylene‐vinyl acetate brands used for custom‐fitted mouthguard fabrication on the stress and strain during an impact

Abstract

Background/Aim The use of custom‐fitted mouthguards can effectively prevent dentoalveolar trauma during sports practice. The aims of this study were to (1) Evaluate the elastic modulus of different EVA commercial brands used for custom‐fitted mouthguards, and (2) Evaluate whether the different EVA brands can influence the stress and strain generated during an impact simulated by three‐dimensional finite element analysis. Methods The elastic modulus of five EVA commercial brands (Essence®, Bio‐Art®, Proform®, PolyShok®, and Erkodent®) were calculated through uniaxial tensile tests. The obtained values were evaluated statistically by Kruskal–Wallis and Dunn's test. A three‐dimensional model of the anterior maxilla was created using the Rhinoceros 5.0. A 3 mm custom‐fitted mouthguard was simulated. The three‐dimensional volumetric mesh was generated using the Patran software (MSC.Software) with isoparametrics, 4‐noded tetrahedral elements, and exported to Marc/Mentat (MSC.Software) as element number 134. A non‐linear dynamic impact analysis was performed in which a rigid object struck the central incisor at a speed of 5 m/s. The stresses were evaluated by the modified von Mises criteria, and the strains were also recorded. Results Statistically significant differences were observed for elastic modulus values (p < .001). Median values and the results of the Dunn's test were Essence® (38.1 A), Bio‐Art® (34.9 AB), Proform® (20.8 BC), PolyShok® (17.4 CD), and Erkodent® (15.0 D) (different capital letters mean statistical differences among the groups). Stresses and strains generated in the model with mouthguards were significantly lower than the model without a mouthguard regardless of the commercial brand. There was no significant difference in the stress and strain on the enamel and dentin with the different EVA brands. The shock absorption ability was high for all the brands (more than 80%). Conclusion The custom‐fitted mouthguards, independently of the commercial brand, reduced stresses and strains during the impact.

Sports mouthguard overview: Materials, fabrication techniques, existing standards, and future research needs

“…55 A further important consideration is that commercial SM brands may contain different proprietary EVA copolymer percentage content that may affect performance. [59][60][61] EVA material variations have included silver nanoparticles to add antibacterial properties, 62 and additions to enhance shock absorbance have included porous rubber, silicone interlayers, 63 silicon nylon mesh, 64,65 and urethane modifications. 66 Additional performance-enhancing adaptations have included internal air cells either alone, 67,68 or combined with hard material inserts, 69 closed cell foam, 67 A-silicone interlayers, 70 and "honeycomb" internal EVA mesh.…”

“…85 While largely underutilized, finite element analysis (FEA) of SM function has been described that allows the in silico computational, non-destructive virtual analysis of complex structures that would be difficult to derive using in vitro methods. 9,10,18,59,68,75,86 Both 2D FEA that can perform planar stress and strain analysis has been reported, 9 as well as 3D FEA that can evaluate biomechanical responses and stress dissipation over wider areas. 10,59,68,75,86 Furthermore, SM materials have also been characterized using thermal analysis techniques to investigate material properties at intraoral temperatures.…”

“…9,10,18,59,68,75,86 Both 2D FEA that can perform planar stress and strain analysis has been reported, 9 as well as 3D FEA that can evaluate biomechanical responses and stress dissipation over wider areas. 10,59,68,75,86 Furthermore, SM materials have also been characterized using thermal analysis techniques to investigate material properties at intraoral temperatures. 22,60…”

“…Materials for SM fabrication have traditionally been ethylene vinyl acetate (EVA), 53–56 a thermoplastic polymer material reported as possessing properties of shock absorbance and distribution of absorbed energy, 57,58 but also containing some mechanical and thermal property limitations 55 . A further important consideration is that commercial SM brands may contain different proprietary EVA copolymer percentage content that may affect performance 59–61 . EVA material variations have included silver nanoparticles to add antibacterial properties, 62 and additions to enhance shock absorbance have included porous rubber, silicone interlayers, 63 silicon nylon mesh, 64,65 and urethane modifications 66 .…”

“…Stress absorption assessments have included strain gauge sensors, 18 Fiber Bragg grating strain sensors, 18 film sensors, 83 laser triangulation sensors, 65 laser Doppler vibrometers, 84 solid‐state NMR pulse measurements, 53 and 3D image correlation strain analysis 85 . While largely underutilized, finite element analysis (FEA) of SM function has been described that allows the in silico computational, non‐destructive virtual analysis of complex structures that would be difficult to derive using in vitro methods 9,10,18,59,68,75,86 . Both 2D FEA that can perform planar stress and strain analysis has been reported, 9 as well as 3D FEA that can evaluate biomechanical responses and stress dissipation over wider areas 10,59,68,75,86 .…”