Thermoforming technique for suppressing reduction in mouthguard thickness: Part 2 Effect of model height and model moving distance.

Abstract

BACKGROUND/AIM Wearing a mouthguard reduces the risk of sports-related injuries, but the material and thickness of the mouthguard has a substantial impact on its effectiveness and safety. The aim of this study was to establish a thermoforming technique in which the model position is moved just before formation to suppress the reduction in thickness. For that end, the effects of model height and model moving distance to the mouthguard thickness were investigated. MATERIALS AND METHODS Ethylene-vinyl-acetate sheets of 4.0-mm-thick and a vacuum forming machine were used. Three hard plaster models were trimmed so that the height of the anterior teeth was 25 mm, 30 mm, and 35 mm. Model position (MP) was 40 mm from the front of the forming unit. The sheet was softened until it sagged 15 mm, after which the sheet frame was lowered to cover the model. The model was then pushed from behind to move it forward and the vacuum was switched on. The model was moved distances of 20 mm, 25 mm, or 30 mm whereas a control model was not moved. Thickness after formation was measured with a specialized caliper. Differences in mouthguard thickness due to model height and moving distance were analyzed by two-way ANOVA and Bonferroni's multiple comparison tests. RESULTS Sheet thickness decreased as the model height increased. Each MP condition was significantly thicker than the control in each model. There was no significant difference among MP conditions except for the buccal surface. CONCLUSIONS Moving the model forward by 20 mm or more just before formation is useful to secure the labial thickness of the mouthguard. This thermoforming technique increases the thickness by 1.5 times or more compared with the normal forming method, regardless of model height.