Teeth clenching during exercise is important for sports performance and health. Recently, several mouth guard (MG)-type wearable devices for exercise were studied because they do not disrupt the exercise. In this study, we developed a wearable MG device with force sensors on both sides of the maxillary first molars to monitor teeth clenching. The force sensor output increased linearly up to 70 N. In four simple occlusion tests, the trends exhibited by the outputs of the MG sensor were consistent with those of an electromyogram (EMG), and the MG device featured sufficient temporal resolution to measure the timing of teeth clenching. When the jaw moved, the MG sensor outputs depended on the sensor position. The MG sensor output from the teeth-grinding test agreed with the video-motion analysis results. It was comparatively difficult to use the EMG because it contained a significant noise level. Finally, the usefulness of the MG sensor was confirmed through an exercise tolerance test. This study indicated that the developed wearable MG device is useful for monitoring clenching timing and duration, and the degree of clenching during exercise, which can contribute to explaining the relationship between teeth clenching and sports performance.

The aim of this study is to consider the hypothesis that wearing mouthguards (MGs) from a young age helps to shape players’ habit of continuing to wear MGs as adults. In addition, we consider the mandatory rule of wearing mouthguards in the youth category on the future wearing rates of mouthguards. Eighty-five Japanese male amateur rugby players were included in this study. We examined the relationship between the wearing rates of mouthguards when participants were high school students and as adults (in 2018) using a questionnaire. Collected data were classified into categories (age, mouthguard type, and applied mandatory rule or not), and their relationships were analyzed. The wearing rate of mouthguards in high school was significantly related to the wearing rate of mouthguards in adulthood (χ2 = 12.1, p < 0.01). The mandatory rule to wear mouthguards at high school was related to the wearing rates of mouthguards as adults, but not significantly (χ2 = 3.42, p = 0.06). Participants’ mouthguard wearing rates as adults were affected by their high school wearing rates. The mandatory rule of wearing mouthguards in the youth category may be somewhat effective for improving mouthguard wearing rates; however, it is more important to provide knowledge about their importance.

Background: A delay in muscle repair interferes with the effect of training or exercise; therefore, it is important to identify the factors that delay muscle repair. P. gingivalis, one of the most common periodontal disease pathogens, has the potential to inhibit muscle repair after training, as inferred from a previous study. To assess the expression of satellite cells in this in vivo study, we evaluated the relationship between P. gingivalis and muscle regeneration after training. Methods: A total of 20 male Wistar rats (eight weeks in age) were randomly divided into two groups: one orally administered sonicated P. gingivalis four times per week for six weeks (PG group) and one given no treatment (NT group). After four weeks of training using a treadmill, the gastrocnemius was evaluated using histology of the cross-sectional area (CSA) of myotubes and immunohistochemistry of the expression of skeletal muscle satellite cells. In addition, an endurance test was performed a day before euthanization. Results: The CSA and expression of Pax7+/MyoD− and Pax7+/MyoD+ cells were not significantly different between the groups. However, the expression of Pax7−/MyoD+ cells and running time until exhaustion were significantly lower in the PG group. Conclusions: Infection with P. gingivalis likely interferes with muscle repair after training.