Effect of the anteroposterior position of the model on fabricated mouthguard thickness: Part 2 Influence of sheet thickness and material.

Abstract

Mouthguards can reduce the risk of sports-related injuries, but the sheet material and thickness have a large effect on their efficacy and safety. The aim of this study was to investigate the thickness of molded mouthguards when the model position on the forming table was changed stepwise in the anteroposterior direction for different sheet thicknesses and materials. Ethylene vinyl acetate sheets and olefin copolymer sheets with 4.0 or 2.0mm thick were used for thermoforming by a pressure-forming machine. The working model was trimmed to the height of 25mm at the maxillary central incisor and 20mm at first molar. The model was placed with its anterior rim positioned 40, 30, 25, 20, or 10mm from the front of the sheet frame. Sheet thickness after fabrication was determined for the incisal edge, labial surface, and buccal surface using a specialized caliper. The differences of the model position on the thickness reduction were analyzed by two-way analysis of variance and Bonferroni's multiple comparison tests. Thickness reductions at the incisal edge, labial surface, and buccal surface were about -60%, -50%, and -40%, respectively; for a distance of 25mm up to the height of the anterior part of the model and the frame from the model rim, the 4.0 and 2.0mm sheets showed similar thickness reduction. When the model was moved forward, the anterior thickness reduction of the 2.0-mm-thick sheet increased to larger than that of the 4.0-mm-thick sheet. The thickness reduction of the mouthguard was not affected by the sheet material and thickness when the distance from the model to the frame was the same. However, when the distance between the model and the frame decreased, the thickness reduction of the adjacent portion of the model increased, such that the influence was larger in thin sheets.