Thermoforming technique for maintaining the thickness of single-layer mouthguard during pressure formation

Using mouthguards can reduce the risk of injury when playing sports, 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 moving the model position just before formation in the pressure forming technique to maintain the thickness of a single-layer mouthguard.

A 4.0-mm-thick ethylene vinyl acetate (EVA) mouthguard sheet (diameter: 125 mm) and a pressure forming machine were used. The working model was placed with its anterior rim positioned 40 mm from the front of the forming table. The sheets were placed in the forming table with the sheet extrusion direction either vertical (V) or parallel (P) to the model's centerline. Two molding methods were compared: (a) The sheet was formed when it sagged 15 mm (control) and (b) the sheet was covered on the model when it sagged 15 mm, next the model was pushed forward 20 mm, and the sheet was then formed (MP). Mouthguard thickness was measured for the labial surface, palatal surface, cusp, and buccal surface using a specialized caliper. Thickness differences according to molding methods and sheet extrusion directions were analyzed by two-way ANOVA.

The thicknesses of the labial surface, cusp, and buccal surface were significantly larger in MP than in the control (P < 0.01). In particular, the thickness differences caused by the molding method were large on the labial and buccal surfaces: For the control, the thicknesses were 1.9 ± 0.03 and 2.1 ± 0.02 mm, whereas for MP, they were 3.2 ± 0.03 and 2.9 ± 0.03 mm, respectively.

The molding method of moving the model forward just before formation was useful as a thermoforming technique for maintaining the thickness of single-layer mouthguards during pressure forming with 4.0-mm-thick EVA sheet. This method produced labial and buccal thicknesses of 3.2 ± 0.03 and 2.9 ± 0.03 mm.