The strength of the intraoral and extraoral muscles that assist the function of tooth and jaw movement during mastication is important for performing oral function. The aim of this study was to investigate the usefulness of gum chewing training to improve the swallowing and feeding function. In experiment 1, the differences in maximum tongue pressure (TP) and cheek pressure (CP) at the measurement time point for both groups with and without training were examined. We instructed subjects to perform gum chewing training 3 times daily for 3 months. TP and CP were measured before training and at 1, 2, and 3 months after starting training. In experiment 2, the changes of TP and CP based on the sex and duration of training were examined. The effect of the training was evaluated before training, at 2 weeks and 1, 2, and 3 months after starting training, and at 1 and 3 months after cessation of training. Experiment 1 showed TP and CP increased with the progress of continuous training. In experiment 2, TP and CP were higher in men than in women and markedly increased at 2 weeks and 1 month in both sexes. After cessation of training, TP and CP tended to decrease, but there was no significant difference between 3 months after starting training, and also significantly higher than before training. This study suggested that gum chewing training is a useful to improve the swallowing and feeding function.

目的 : スポーツ時の顎口腔領域の外傷予防には, マウスガードの装着が有効である. 本研究では, 厚さの異なる2種類のシートの成形後の厚みについて比較検討を行うことを目的とした. 方法 : マウスガードシートに10mm四方の格子を印記し, 各格子の厚さをメジャリングディバイス®を用いて測定した. マウスガードシートは2mmおよび4mmの厚さのものを用い, 2種類の厚さのマウスガードシートの成形後のシート各部の厚みの違いをWilcoxon符号付順位和検定およびt 検定を用いて分析した. さらに, 成形後のシート各部の延びと厚みの関係を回帰分析により検討した. 結果 : シートの模型圧接部は, すべての部位で厚みが減少した. シート各部の厚さの変化は2mmシートと4mmシートで同様であった. 前歯部および口蓋部では, 2mmシートのほうが4mmシートに比較して厚みの変化率が大きかった (p < 0.01). 臼歯部の厚みの変化率は, 2mmシートと4mmシートで違いは認められなかった. 延びと厚みの関係は, 二次関数で表された. 結論 : 本研究の結果, 前歯部および口蓋部の厚みの減少率は2mmシートのほうが4mmシートよりも大きくなり, 臼歯部の厚みの減少率はシートの厚さによる違いがないことが明らかとなった.

The aim of this study was to determine the color difference of mouthguard in hardness, water sorption and thickness after forming EVA sheets. Six different colors of sheets were tested for each of three manufacturers. The materials used in this study were mouthguard sheets made by three manufacturers. Each manufacturer supplied six colors: clear, white, yellow, blue, red, and black. Shore A hardness and water sorption were measured based on ISO 7619 and 1817, respectively. The thickness after formation was measured by using a measuring device. The differences in hardness, water sorption and thickness after formation were analyzed by two-way analysis of variance. The correlation between the hardness and changes in thickness was analyzed using Pearson's product-moment correlation coefficient. Shore A hardness was different depending upon various colored sheets and manufactures. There were differences in the water sorption depending upon some colored sheet among manufacturers. There was a significant difference in the thickness after formation was found to be dependent upon few colors of the sheets on one manufacturer's product on the anterior teeth and on three products on posterior teeth. A negative correlation between the hardness and the change of thickness was found in two products. The present study suggests that the Shore A hardness and thickness after formation varied depending upon the colors of the EVA sheets and manufactures. A correlation between the hardness and change of thickness was observed in two manufactures that suggests that the hard sheets tend to reduce in thickness greater than that in softer ones.

The aim of this study was to evaluate the change in thickness of the mouthguard sheet due to different heating conditions during fabrication. Mouthguards were fabricated with ethylene vinyl acetate (EVA) sheets (4.0-mm thick) using a vacuum-forming machine, and six conditions which varied the height of the frame above the surface, reversing the sheet while heating, and controlled power on-off of the heater when a specified level of sagging had been attained were used to determine optimal conditions. The working model was trimmed to a height of 20-mm at the incisor and 15-mm at the first molar. Post-molding thickness was determined for the incisal portion (incisal edge and labial surface) and molar portion (cusp, central groove, and buccal surface). Differences in the change in thickness due to heating condition were analyzed using Scheffé's multiple comparison tests. The heating condition which the sheet frame was lowered to and heated at 50mm below the top of the post, the heater was turned off when the sheet sagged by 10mm, and the sheet was molded when the sagging reached 15 mm showed the thickest, what the decrease in the thickness reduction was approximately 0.40-0.44 mm at the incisal, and that was 0.35-0.40 mm at the molar portions. When molding a mouthguard using an EVA sheet, the thickness of the incisal and molar portions of the mouthguard can be maintained by adjusting the height of the sheet frame and heating conditions, which may be clinically useful.