Disinfection and Isotonic Drinks’ Influence on Hardness and Color Stability of Ethylene-Vinyl-Acetate Copolymer Mouthguards Used in Martial Arts: An In Vitro Study

Abstract

This in vitro study aimed to evaluate the hardness and color change of an ethylene-vinyl-acetate copolymer (EVA) material for mouthguards after exposition to different cleaning agent solutions and isotonic drinks. Four hundred samples were prepared and divided into four equinumerous groups (n = 100), in which there were 25 samples from each color of EVA (red, green, blue and white). The hardness, using the digital durometer, and the color coordinates (CIE L*a*b*), using the digital colorimeter, were measured before the first exposition and after 3 months of exposition to spray disinfection and incubation in the oral cavity temperature, or immersion in isotonic drinks. The values of Shore A hardness (HA) and color change (ΔE—calculated by Euclidean distance) were statistically analyzed using the Kolmogorov–Smirnov test, multiple comparison ANOVA/Kruskal–Wallis and appropriate post-hoc tests. Statistically significant changes in color and hardness between the tested groups were demonstrated after the use of agents predestined for disinfecting the surface of mouthguards on the tested samples. There were no statistically significant differences in color and hardness between the groups immersed in isotonic sport drinks potentially consumed by competitors practicing combat sports using mouthguards. Despite the changes in color and hardness after the use of disinfectants, the deviations were minor and limited to specific colors of the EVA plates. The intake of isotonic drinks practically did not change either the color or the hardness of the samples, regardless of the tested color of the EVA plates.