Difference in the thickness of mouthguards fabricated from ethylene-vinyl acetate co-polymer sheets with differently arranged v-shaped grooves

PURPOSE: To investigate the form of mouthguard sheets that best retains its thickness. METHODS: Mouthguards were molded using ethylene-vinyl-acetate (EVA) sheets and a suction-type molding device. Five sheet conditions were compared. These were I-N (Incisal part of the cast positioned at the center - Normal sheet), I-H (Incisal part positioned at the center - Horizontal v-shaped groove 30 mm from the anterior end), I-C (Incisal part positioned at the center - Convexing v-shaped groove toward the back 10-40 mm from the anterior end), C-N (Center part positioned at the center - Normal sheet), and C-C (Center part positioned at the center - Convexing v-shaped groove toward the back 10-30 mm from the anterior end). Post-molding thickness was determined for the incisal (incisal edge and labial surface) and molar portion (cusp, central groove, and buccal surface). Sheets were heated until they sagged 15-mm below the clamp. Scheffé multivariate comparison was performed to compare changes in post-molding thickness among sheet conditions. RESULTS: Post-molding thickness of mouthguard material differed significantly between the two portions; rates of thickness reduction were smaller for I-C and C-C compared with other conditions. There were no significant differences between I-C and C-C at any measurement points. CONCLUSION: The present results suggested that thickness reduction of the EVA sheet material after vacuum-forming may be decreased at both incisal and molar portions if the v-shaped groove with a v-shaped cross section was given in the frontal teeth region of the sheet at the apparatus and materials for this study used.