Effective thermoforming method for maintaining mouthguard thickness with a circular sheet using a circular frame

Mouthguard thickness is important to prevent oral and facial trauma during sports. The aim of this study was to establish an effective thermoforming method for maintaining mouthguard thickness with a circular sheet using a circular frame.

Mouthguards were thermoformed using 4.0-mm-thick ethylene vinyl acetate sheets and a vacuum forming machine. Each sheet was pinched at the top and bottom and stabilized by a circular frame. Two heating conditions were compared: (1) condition N, where the sheet was formed when it sagged 10 mm below the level of the sheet frame at the top of the post, and (2) condition L, where the sheet frame was lowered 50 mm below the ordinary level and heated, and the sheet was formed when it sagged 10 mm. In each heating method, two forming conditions were compared: (1) when the sheet softened, the sheet frame was lowered and formed (condition C; N-C, L-C), and (2) after the sheet frame was lowered, the model was moved forward 20 mm and then formed (condition MP; N-MP, L-MP). Six mouthguards were fabricated for each condition. Thickness differences due to heating conditions and forming conditions were analyzed by the two-way ANOVA and Bonferroni's multiple comparison test.

At the incisal edge and at the labial and buccal surfaces, significant differences were observed among all conditions, and the thicknesses were in the order N-C < L-C < N-MP

The thermoforming method with a circular sheet using a circular frame did not maintain a sufficient thickness only by the method of moving the model position just before formation. However, the results suggest that a single-layer mouthguard with a labial thickness of 3 mm or more could be fabricated by applying the method of lowering the sheet frame and heating the sheet.