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

Abstract

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

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

“…[ared with the vacuum forming machine . However, the current results were the same as those for condition MP in vacuum forming, indicating that condition MP suppresses the decrease in the mouthguard thickness at the labial and buccal surfaces. That is, when a 4.0‐mm‐thick EVA sheet was molded under condition MP, the thicknesses of the mouthguards on the labial and buccal surfaces were 3.1‐3.2 and 2.8‐2.9 mm, respectively, regardless of whether vacuum or pressure forming was used.…”

“…Several other methods have been developed to ensure sufficient mouthguard thickness (eg, temperature, notching of the EVA sheets, and angulation of the model), including a method that controls thickness by moving the model just before sheet forming to compensate for insufficient thickness in the mouthguard anterior portion. This was previously investigated by using a vacuum forming machine and the labial thickness of the mouthguard was 1.7 times thicker (3.1 ± 0.02 mm) than that obtained with the normal forming method when a 4.0‐mm‐thick EVA sheet was used.…”

“…Previously, a thermoforming technique that moves the model position just before vacuum forming has been investigated and that technique was found to be more effective in reducing the mouthguard thickness than the conventional molding method . This method produced a labial thickness of the mouthguard of 3.1 ± 0.02 mm when using 4.0‐mm‐thick ethylene vinyl acetate (EVA) sheet.…”

Movement of model position just before vacuum forming to ensure mouthguard thickness: Part 2 Effect of model moving distance

“…Mouthguards were fabricated from a sheet of ethylene‐vinyl acetate resin (Sports Mouthguard, 127 × 127 × 4 mm, clear; Keystone Dental Inc.). The working model was a maxillary dental model made of dental gypsum that was trimmed to a height of 25 mm and to 20 mm at the central incisor and first molar . The model was allowed to stand at room temperature for at least 48 hours and was completely dry before use.…”

“…Therefore, the height of the model and the setting position of the model on the forming unit affect the thickness . A previous study has focused on this shape change and examined the usefulness of the forming method by moving the model position just before vacuum forming . That study clarified that the sheet stretching during the model formation was suppressed, and the thickness of the mouthguard's anterior and molar portions could be secured.…”