Dependence of Thermoformed Mouthguard Thickness on Model Height in Single-Layer and Laminated Mouthguards

Abstract

The height of the working model affects the mouthguard thickness. The aim of this study was to clarify the difference in the effect of model height on the thickness between single- and double-layered mouthguards. Mouthguards were thermoformed using ethylene-vinyl-acetate sheets and a pressure molding machine. Working models were three hard gypsum models with the height of the anterior part trimmed to 25 mm (model A), 30 mm (model B), and 35 mm (model C). Three molding conditions were compared: a single-layered mouthguard using a 4.0-mm thick-sheet (S4); a double-layered mouthguard using a 3.0-mm-thick sheet on the first-layer and a 2.0-mm-thick sheet on the second-layer (L32); and a double-layered mouthguard using 3.0-mm-thick sheets on first- and second-layers (L33). Analysis was performed by two-way ANOVA and a simple main effect test for the differences in the mouthguard thickness depending on the model height and the molding condition. Under all molding conditions, the labial and buccal thicknesses tended to become thinner as the model height increased, and models B and C were thinner by about 6% - 7% and about 14% - 16% than model A, respectively. The cusp thickness was not affected by the model height in L32 and L33, but in S4, models B and C were thinner about 14% or more than model A. Significant differences were observed among molding conditions, and S4 < L32 < L33 in all models ( P < 0.01). This study suggested that the degree of the decrease in mouthguard thickness due to the increase the model height was similar for the single- and double-layered mouthguards on the labial and buccal sides, and increasing the model height by 5 mm and 10 mm decreased the thickness by about 6% - 7% and about 14% - 16%, respectively. At the cusp, only the single-layered mouthguard was affected by the model height.