Background/Aims: Despite the use of conventional mouthguards, preventable sports-related dental injuries continue to occur. The authors have developed a twolayered ethylene polyvinyl acetate (EVA) mouthguard with a hard polyethylene terephthalate (PET) insert and a buffer space (H&SMG). However, adapting the PET onto the EVA layer requires skill. A light-cured Splint Resin (SRLC) and a glass fiber net (NET) reinforcement appear to resolve this issue. The aim of this study was to investigate whether SRLC with NET could replace PET and find a more practical application for NET. Materials and Methods: A pendulum impact testing machine and a dental model with strain gages were used. Six types of mouthguards were made: one with two laminated EVA blanks (LAM-MG), a three-layer type with a PET insert and an intermediate space (PET-H&SMG), a H&SMG with SRLC insert (LC-H&SMG), and three other types with differential NET-SRLC reinforcement; NET on the outer surface of SRLC, NET on the inner surface of SRLC, and NET on both the outer and inner surfaces. Five mouthguards of each type were fabricated and tested ten times with impact distances of 15 and 30 cm. Forty more impacts were applied to all H&SMGs to confirm the durability of the hard inner layer. Results: All H&SMGs showed significant strain reduction compared to the LAM-MG. PET-H&SMG and the four types of LC-H&SMG exhibited an equally slight strain (approximately 95% shock absorbing ability) in all conditions. During the test against the smaller impact, all H&SMGs showed no cracks. When tested against the stronger impact, only the LC-H&SMG with the reinforced inner surface, the double NETreinforced LC-H&SMG, and the PET-H&SMG remained intact. Conclusion: The NET-reinforced SRLC can replace PET as an intermediate mouthguard material. The NET application, at least on the internal surface, is indispensable for the LC-H&SMG reinforcement.

Objective Mouthguards can prevent and reduce orofacial sports traumas, which occur to the players themselves. However, the effect of mouthguards on skin damage has not been clarified. The present study's purpose was to examine whether the mouthguard can reduce or prevent skin damage caused by teeth (including the difference in mouthguard thickness). Materials and Methods Pigskins, artificial teeth, and Ethylene-vinyl acetate (EVA) mouthguard blanks with 1.5- and 3.0-mm thickness were employed. Each of the two type mouthguards was produced in 10 replicates. Mouthguard incisal thickness and collision touch angle were measured on a PC using imaging software. A pendulum-type machine was used to apply impact. Strain gauges attached to the tooth and impacted plate were used to measure mouthguards' effect on impact stress. Also, a microscope was used to observe the after impacted skin condition, and the extent of damage was assessed as a score. Results The pigskin was ruptured in without mouthguard (NOMG) with presenting the highest damage score, whereas the complete rupture was not seen in the 1.5 mm MG, but the damage of the skin (defeat) was observed. No tissue change was found with the 3 mmMG. In both the flat plate and impact tooth strain, no significant difference was observed between NOMG and 1.5 mmMG. However, 3 mmMG had a significantly smaller value than the other two conditions. These results are likely to be strongly influenced by the mouthguard incisal thicknesses and collision touch angles differences. Conclusion The present study results clarified that two different thickness mouthguards reduced the skin damage, and the thicker mouthguard showed more effectiveness. Therefore, mouthguards may prevent the wearer's stomatognathic system's trauma and avoid damage to the skin of other athletes they are playing with. This effect seems to be an essential basis for explaining the necessity of using mouthguards for others besides full-contact sports.

Background/Aim During sports activities, teeth‐related contact can cause injury to both ally and opponent players, which can lead to potential infections and aesthetic problems. However, the extent of such injuries remains unclear. This study aimed to clarify the frequency and situation of head injuries caused by teeth (HICBT) occurring under the supervision of schools in Japan. Material and Methods HICBT records were extracted from the Japan Sport Council data on head injuries occurring reported during the 7‐year period from 2012 to 2018 under the supervision of schools in Japan. Results Of the total 463,527 head injury cases during the study period, 4495 cases (approximately 1%) were HICBT. Of the HICBT cases, 3650 (81.20%) were related to sports and athletic activity. Such injuries were reported to occur most often during basketball with a rate of 57.07% and 50.43%; soccer/futsal was the next most common sport with a rate of 13.38% and 24.01% in junior high school and high school students. Tag games were responsible for a similar number of HICBT cases at 22.73% and 39.03% in kindergartens and elementary school students. Conclusions A total of 4495 cases of HICBT were identified, accounting for about 1% of all head injuries under the supervision of schools in Japan during the study period. This result reminds us that our teeth could be the weapon against the players during sports events. HICBTs occurring during basketball and soccer/futsal, in which mouthguards are not mandatory, were conspicuous among junior and senior high school students. Active use of mouthguards in various sports will protect players as well as their teammates and opponents. Sports dentists should encourage the revision of rules, such as mandating the use of mouthguards, in popular sports with a high incidence of HICBT, such as basketball and soccer/futsal.