Thermoforming method to effectively maintain mouthguard thickness: Effect of moving the model position just before vacuum formation.

<bold>Background/aims: </bold>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 effect of the thermoforming technique that moves the model position just before vacuum formation.<bold>Materials and Methods: </bold>Ethylene vinyl acetate sheets of 4.0-mm thickness and a vacuum forming machine were used. The working model was placed with its anterior rim positioned 40 mm from the front of the forming table. Three forming conditions were compared: (a) The sheet was formed when it sagged 15 mm at the top of the post under normal conditions (control); (b) the sheet frame was lowered to and heated at 50 mm from the level of ordinary use, and the sheet was formed when it sagged 15 mm (LH); and (c) the sheet frame at the top of the post was lowered and covered on the model when it sagged 15 mm. Subsequently, the rear side of the model was pushed to move it forward 20 mm, and it was then formed (MP). Sheet thickness after fabrication was determined for the incisal edge, labial surface, and buccal surface using a specialized caliper accurate to 0.1 mm. Thickness differences among forming conditions were analyzed by one-way ANOVA and Bonferroni's multiple comparison tests.<bold>Results: </bold>A significant difference was observed for all measurement points, and the thickness after formation increased in the order of control, LH, and MP. Particularly on the labial surface, MP was able to yield about 1.7 times the thickness (about 3.1 mm) of the control.<bold>Conclusion: </bold>The forming method of moving the model forward just before vacuum formation was effective for suppressing the mouthguard thickness reduction, which is capable of securing the labial thickness at 3 mm or more with a single layer. [ABSTRACT FROM AUTHOR]