Comparison of energy absorption and thermal characteristics of three different mouthguard materials

Mouthguards are used for protecting head-neck region against impact. Energy absorption and structural changes as a function of temperature are important.The aims of this study were; evaluating energy absorption of mouthguard-materials, investigating the structural transformations as a function of temperature, evaluating the effect of aqueous environment on energy absorption and structural characteristics of mouthguard-materials.The impact test performance of mouthguard-materials was evaluated using the procedure in ASTM Standard D3763. Different mouthguard-materials (EVA, ProForm? and PolyShok?) were included in the study. Specimens prepared following the manufacturer recommendations were conditioned for 1 hr in 37ºC deionized water and loaded at 32.20 km/h. Large-diameter and small-diameter support rings were used. Two dry specimens of each material were also tested. Energy absorption was determined from the area under the force-time curve and results were compared using ANOVA and Tukey-Kramer HSD test. Small samples taken from areas close to the impact zone were obtained to perform TMDSC test from ?20° to 150°C at a heating rate of 1°C/minute.For the large-diameter support ring, energy absorption (mean±SD, cm?kg/cm): EVA, 599.8±263.5; Pro form?, 598.8±61.5; PolyShok?, 575.4±89.8. For the small-diameter support ring, energy absorption was: EVA, 764.8±75.7; ProForm?, 593.3±141.5; PolyShok?, 677.1±154.6. Four endothermic peaks were observed on TMDSC curves for conventional EVA while three peaks were observed for PolyShok and ProForm, TMDSC curves showed similarities for all three materials. The lowest-temperature endothermic transformation was near body temperature.There was no significant difference in energy absorption for the three mouthguard-materials and the two support ring sizes. The energy absorption was greater for dry specimens. The small difference in thermal behavior for PolyShok is attributed to disruption of EVA crystal formation.