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

Abstract

Background/Aim 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. Materials and Methods 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. Results 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. Conclusion 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.

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

“…9,[15][16]22,29,[33][34][35][36][37][38][39] The method of controlling the thickness by moving the model position just before formation is particularly useful. 9,15,33 This method suppresses the decrease in thickness of the sheet by reducing the elongation of the sheet during formation. That is, if the length of the original sheet is insufficient for the amount of sheet deformation (ie the sum of the model height and the distance from the model edge to the sheet frame), the sheet is elongated further and its thickness is decreased.…”

Thermoforming Technique for Suppressing Reduction in Mouthguard Thickness

“…We furthermore examined the effect of changing the distance the model moved and found that moving the model a distance of more than 20 mm was most effective at preserving thickness [17]. And, the pressure molding machine achieved the same thickness as the vacuum forming machine [17]. From these, it was inferred that this thermoforming method could be obtained with a sufficient thickness with a single layer.…”

“…In contrast, the palate side, which affects the feeling of wearing mouthguards, became thinner [17]. We furthermore examined the effect of changing the distance the model moved and found that moving the model a distance of more than 20 mm was most effective at preserving thickness [17]. And, the pressure molding machine achieved the same thickness as the vacuum forming machine [17].…”

“…In the MP technique, the thickness of the labial surface and the buccal surface were maintained by suppressing the stretching of the sheet during model formation [15] [17] [18]. In contrast, the palate side, which affects the feeling of wearing mouthguards, became thinner [17]. We furthermore examined the effect of changing the distance the model moved and found that moving the model a distance of more than 20 mm was most effective at preserving thickness [17].…”

“…Several methods have been investigated for suppressing the reduction in thickness of mouthguards [9]- [18], including heating [9] [10] [13], adjusting the model angle [14], using a V-shaped grooved sheet [11] or notched sheet [16], and moving the model position just before forming [15] [17] [18]. The results showed that moving the model position just before vacuum forming yielded the required thickness more effectively than the heating method or adjusting the model angle, and was easier than using a V-shaped grooved sheet or a notched sheet [17] [18].…”