Abstract
Mouthguard thickness is affected by the softened state of the sheet during thermoforming. The aim of this study is to establish an effective method for controlling the softened state of the sheet to prevent the mouthguard thickness from decreasing during mouthguard fabrication using a vacuum-forming machine. Mouthguards were thermoformed using an ethylene-vinyl acetate sheet (thickness: 4.0 mm) and a vacuum-forming machine. The working model was trimmed to the anterior height of 25 mm and the posterior height of 20 mm. The following two heating methods were compared: 1) the sheet was formed when it sagged 15 mm below the level of the sheet frame at the top of the post (condition T); and 2) the sheet frame was lowered to and heated at 50 mm below its usual height and the sheet was formed when it sagged 15 mm below the level of the sheet frame (condition L). For each heating method, the vacuum was applied immediately (T0, L0) or 5 s (T5, L5) after the sheet frame was lowered to the forming unit. The sheet surface temperature immediately before the vacuum was applied under each condition was measured. The differences in mouthguard thickness due to forming conditions were analyzed by one-way ANOVA and Bonferroni’s multiple comparison tests. The temperature difference between the center and the posterior depending on the condition decreased in the order T0 > T5 > L0 > L5, and that was 20°C or higher for T0 and T5, and 10°C or less for L0 and L5. At the incisal edge and the cusp, L0 and L5 were significantly thicker than T0. No significant differences were observed between conditions L0 and L5 at any measurement points. For the labial and buccal surfaces, significant differences in thicknesses among all conditions, except L0 and L5, were observed and were in the order T0 < T5 < L0 and L5. This study was suggested that the lowering the sheet frame and heating was more effective than adjusting the vacuum timing for uniform softening of the sheet.
Highlights
Wearing a mouthguard during sports is effective in preventing and reducing trauma, and the material and thickness of the mouthguard greatly affect its effectiveness and safety [1] [2]
The temperature difference between the center and the posterior depending on the condition decreased in the order T0 > T5 > L0 > L5, and that was 20 ̊C or higher for T0 and T5, and 10 ̊C or less for L0 and L5
Differences in mouthguard thickness depending on the heating method of the sheet were observed at
Summary
Wearing a mouthguard during sports is effective in preventing and reducing trauma, and the material and thickness of the mouthguard greatly affect its effectiveness and safety [1] [2]. When fabricating a mouthguard by thermoforming, the heating state of the sheet affects the thickness of the mouthguard [5] [6] [7]. When a mouthguard sheet is heated by a forming machine with conventional methods, there are temperature differences between different parts of the sheet. The sheet is partially stretched when it makes contact with the model and the thickness is greatly reduced when the unevenly softened sheet is formed [5] [6]. Inverting the sheet during heating [7] or delaying the vacuum-forming timing by several seconds [9] suppressed thinning
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