3Dプリント製および熱成形EVAカスタムメイドマウスガードの生体力学的解析：実験および有限要素解析

3D printed materials have been evaluated for fabricating mouthguards; however, little is known about their biomechanical performance in preventing dental trauma. This study aimed to compare two 3D printed polymers and three ethylene vinyl acetate (EVA) sheets used for mouthguard fabrication regarding their mechanical properties and stress-strain behavior during impact, analyzed through finite element analysis (FEA).

Two 3D printed polymers, KeyGuard (Keystone) and DimaPrint (Kulzer), and three EVA sheets, Bio-art, Essence Dental, and Proform, were used to create the specimens following ISO 37-II (n = 10). Shore A hardness was measured on the surface. The breaking force (F, N), elongation (EL, %), ultimate tensile strength (UTS, MPa), and elastic modulus (E, MPa) were measured using a universal testing machine (EMIC). Density (ρ, g/cm³) was determined using the test method following ASTM D792. Poisson's ratio was calculated by using axial tensile tests following ASTM D638. Scanning electron microscopy was used to examine the surfaces of EVAs and 3D printed polymers. A two-dimensional finite element model of the maxillary structure and upper incisor was evaluated with and without a 4.0 mm mouthguard made from each material. An impact simulation was performed by striking the upper incisor with a rigid surface at 1 m/s (3.6 km/h). Strain and modified von Mises stress distributions were evaluated, and mouthguard displacement relative to the tooth was calculated.

One-way ANOVA revealed significant differences among the tested mouthguards for all evaluated parameters (p < 0.01). Essence Dental showed the highest and DimaPrint the lowest values of F and UTS values (p < 0.01). Proform was the highest, and DimaPrint had the lowest EL values (p < 0.01). DimaPrint and KeyGuard had the highest, and Proform had the lowest E values (p < 0.01). KeyGuard, Essence Dental, and Bio-art had higher Shore A values than Proform and DimaPrint (p < 0.01). The 3D printed polymer group had significantly higher Poisson's ratio values than EVAs. The density values were similar for all tested materials (p = 0.055). The absence of a mouthguard led to greater stress and strain on the impacted tooth. All mouthguards significantly reduced these values, showing comparable shock-absorbing capacity. Displacement was generally lower in the buccal region and increased toward the palatal side.

Although the 3D-printed polymers exhibited mechanical properties different from EVA materials, all mouthguards demonstrated similar effectiveness for reducing stress and strain on the impacted tooth, indicating comparable protection against dental trauma.