Shock absorption and dispersion capability of a novel five-layer mouthguard sheet material.

There is a growing need for a mouthguard sheet material with higher shock absorption and dispersion capacity than those obtained by conventional materials. A five-layer mouthguard sheet material was previously developed using laminated ethylene vinyl acetate and polyolefin copolymer resin. In this study, the shock absorption capacity and dispersion capability of the new sheet material were investigated and compared with those of other materials. Impact testing for the new sheet material showed that the force required to displace the sheet by 1 mm was significantly higher at all thicknesses (p<0.001), whereas the puncture energy and displacement were significantly lower than those for ethylene vinyl acetate (p<0.05). The five-layer mouthguard sheet material successfully absorbed and resisted shock. Therefore, the sheet material potentially increases resistance to applied deformation in teeth and alveolar bone and maintains structure. The five-layer sheet material could expand the range of mouthguard products and help prevent oral trauma.

Quantitative text analysis of the mechanisms of tooth injury: Analysis of accidents in five sports that occurred in 15 years under school control.

BACKGROUND/AIM: Dental trauma may occur in school settings and it can impact patients' quality of life. Analysis of the occurrences of dental trauma is essential in identifying preventive methods. There are numerous reports of such accidents but most are quantitative analyses with limited data. The aim of this study was to extract information on the mechanisms of injuries that leads to prevention by performing a qualitative analysis of the occurrence of dental trauma. MATERIAL AND METHODS: After screening 7684 cases of dental injuries that occured in schools and were reported to the Japan Sports Council between 2005 and 2020, 533 detailed descriptions of injuries that occurred during sports were included. Quantitative text analysis was performed on the target data by performing statistical analysis, extracting frequently used words, and creating a co-occurrence network. Injury mechanisms were evaluated based on appearance of words. RESULTS: Dental injuries occurred frequently in five sports included in the survey. They were in order of decreasing frequency: baseball, basketball, soccer, volleyball, and rugby. Males were injured more often in all sports other than volleyball. The number of accidents increased in all sports among high school students. The frequent word list and co-occurrence network were different for each sport. This allowed typical accident occurrence mechanisms to be extracted for these five sports. CONCLUSIONS: Typical accident occurrence mechanisms were extracted from quantitative text analysis targeting free texts on the occurrence of accidents for five sports. Quantitative text analysis is useful for the evaluation of accident cases, which may aid in accident prevention.

Continuous Oral Administration of Sonicated P. gingivalis Delays Rat Skeletal Muscle Healing Post-Treadmill Training.

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.

Case Report: Psychoacoustic Analysis of a Clarinet Performance With a Custom-Made Soft Lip Shield Worn to Prevent Mucosal Erosion of Lower Lip.

Introduction: Wind instrument players sometimes suffer from erosion of the mucous membrane of the lip. This is caused by the action and pressure of the mouthpiece of the wind instrument against teeth. To address this problem, a lip shield is fitted over the dental arch to prevent direct contact between the lips and teeth. However, there are a few studies on the influence of the lip shield on the acoustics of wind instruments. The purpose of this study was to analyze the psychoacoustics of a clarinet performance with the player wearing a custom-made soft lip shield to prevent mucosal erosion of the lower lip. Case Description: A lip shield was custom-made with a soft thermoplastic material for a female clarinetist who complained of mucosal erosion and pain of the lower lip. The psychoacoustics of her musical performance played in different dynamics, fortissimo, mezzo forte and pianissimo were analyzed, including loudness and sharpness. A self-evaluation questionnaire with items rated on a 10-point scale was administered. After wearing the lip shield, the patient reported that the mucosal erosion and pain of her lower lip when playing clarinet resolved. The lip shield had little effect on the loudness. There was a slight decrease in sharpness when the lip shield was worn compared to when it was not, describing the reduction of high frequencies. Furthermore, fewer variations in sharpness between the tones were observed. Conclusion: The results suggest that lip shields made of soft materials can eliminate mucosal erosion and pain of the lower lip while having little effect on performance, although, a slight change in timbre is possible.

Useful design of custom-made mouthguard for athletes undergoing orthodontic treatment with brackets and wires.

BACKGROUND/PURPOSE: Custom-made mouthguards (MGs) are strongly recommended for athletes during sports activities to prevent dental injuries. Athletes undergoing orthodontic treatment and wearing brackets require specially designed MGs for better protection and to create more space that will not hinder the planned orthodontic tooth movement. The purpose of this study was to fabricate effective, specially designed, custom-made MGs for patients or athletes with ongoing orthodontic treatment and to evaluate the shock absorption abilities of these MGs by an in vitro comparison of three different designs. MATERIALS AND METHODS: Three different types of specially designed, double-layered MGs, (i) creating inter bracket space inside the MG, (ii) embedding silicon wax inside the MG, and (iii) creating a buffer space with additional hard insertion, were fabricated from a simulated bracket attached model. Impact test was performed using a free-falling object on a vertical rod, and the strain-gauge system was used to assess the strain on the dentition with the MGs for the comparison of the shock absorption abilities of the three types. Analysis of variance at a significance level of 5% and multiple comparisons were performed for statistical analysis. RESULTS: The strains on the dentition with the MG creating buffer space with hard insertion were significantly lower than those with the other two types of MG (P < 0.001). CONCLUSION: Insertion of a hard material and ensuring buffer space between the MG and the teeth and/or appliance was more effective than other methods of fabricating custom-made MGs to prevent sports-related traumatic dental injuries in athletes undergoing orthodontic treatment.

Antibacterial effect of a disinfectant spray for sports mouthguards on Streptococcus sobrinus.

BACKGROUND: Mouthguard (MG) disinfectant sprays are available for maintaining MG hygiene. The effect of these sprays against Streptococcus sobrinus is still unknown. The purpose of this study was to evaluate the antibacterial effect of an MG disinfectant spray against S. sobrinus using the modified ISO 22196 standard. MATERIALS AND METHODS: In this in vitro study, we used the following treatment groups for antibacterial testing: MG spray-1 (left in spray for 30 s), MG spray-2 (60 s), and control (n = 4). All analyses were performed at a statistically significant level (P = 0.05) using JMP® 14. RESULTS: The log colony-forming units of the MG spray-2 group were significantly lower than those of the other groups. The antibacterial activity of MG spray-2 against S. sobrinus was >2.1. CONCLUSION: We confirmed the antibacterial effect of the MG spray against S. sobrinus, and it was influenced by the treatment duration, with the optimum effect at a longer duration.

Correction: Aung et al. Air Permeability, Shock Absorption Ability, and Flexural Strength of 3D-Printed Perforated ABS Polymer Sheets with 3D-Knitted Fabric Cushioning for Sports Face Guard Applications. Polymers 2021, 13, 1879.

Error in Figures 3 and 6 [...].

Air Permeability, Shock Absorption Ability, and Flexural Strength of 3D-Printed Perforated ABS Polymer Sheets with 3D-Knitted Fabric Cushioning for Sports Face Guard Applications.

Sports face guards (FGs) are devices that protect athletes from maxillofacial injury or ensure rapid return to play following orofacial damage. Conventional FGs are uncomfortable to wear owing to stuffiness caused by poor ventilation and often slip off due to increase in weight due to absorption of moisture from perspiration, lowering players' performance. Herein, combinations of 3D-printed perforated acrylonitrile butadiene styrene (ABS) polymer sheets and 3D-knitted fabrics with honeycomb structures as cushioning materials were investigated to balance better wearing feel and mechanical properties. The flexural strength, weight, and shock absorption ability of, and air flow rate through, the ABS sheets with five different perforation patterns were evaluated and compared with those of conventional FG materials comprising a combination of polycaprolactone sheets for the medical splint and polychloroprene rubber for the cushioning material. The ABS sheets having 10% open area and 2.52 mm round holes, combined with knitted fabric cushioning, exhibited the requisite shock absorbing, higher air permeability, and lower weight properties than the conventional materials. Our results suggest that FGs fabricated using combinations of 3D-printed perforated ABS polymer sheets and 3D-knitted fabrics with honeycomb structures may impart enhanced wearing comfort for athletes.

Use of the fiberglass reinforcement method in thermoplastic mouthguard materials to improve flexural properties for enhancement of functionality.

The purpose of this study was to evaluate the application of fiberglass reinforcement method in thermoplastic mouthguard materials to improve flexural properties and adhesive strength. Commonly used two types of commercial mouth guard materials (ethylene-vinyl acetate copolymer-based and polyolefin-based) were reinforced with glass fiber clothes by two-step hot press. Flexural strength and adhesive strength with each base material were examine via three-point bending test and delamination test, respectively. Ethylene-vinyl acetate copolymer-based fiberglass-reinforced material has significantly greater adhesive strength with base material and improvement of flexural properties compared with polyolefin-based material. These results suggest that flexural properties of both conventional commercial mouthguard materials were improved when the glass-fiber-reinforced method was applied to reinforce mouthguard materials, and more, ethylene-vinyl acetate copolymer was more desirable for the base material.

Development of a Wearable Mouth Guard Device for Monitoring Teeth Clenching during Exercise.

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.

Thickness change and deformation of custom-made mouthguards after two years of use by Bangladeshi field hockey players.

BACKGROUND/AIM: Sports mouthguards are effective devices that prevent dental trauma in sports activities. Players should change mouthguards on a regular basis because of thickness reduction and shape deformation. However, there is no guidance regarding the best timing to change mouthguards. The aims of this study were to analyze the thickness change and deformation of mouthguards after 2 years of use in Bangladesh field hockey players and to consider appropriate evaluation criteria. MATERIAL AND METHODS: Fifty-seven field hockey players belonging to the Bangladesh Sports Education Institute participated in this study. Participants were provided with double-layered mouthguards made of polyolefin-based material using a vacuum-forming machine. Mouthguards were fabricated using 2-mm-thick sheet as the first layer and 3-mm-thick sheet as the second layer. Players used the mouthguards for 2 years. Before and after using the mouthguards, the thicknesses of nine areas were measured. In addition, the lengths of five areas were used to analyze shape deformation. RESULTS: After 2 years, the thicknesses of all measured areas had significantly reduced, and the lengths had significantly increased. Thickness reduction of the posterior-occlusal and anterior-incisal areas and deformation of the posterior-buccal and posterior-palatal areas were significantly larger than those in other measured areas. CONCLUSIONS: Mouthguards should be changed on a regular basis to minimize thickness reduction and deformation. Occlusal and incisal thickness and length of the buccal-posterior area and the palatal-posterior area are factors to be considered in establishing guidelines regarding the timing of mouthguard change.

Effectiveness of computer-assisted learning in sports dentistry: studies over a multiple-year period and at two universities.

INTRODUCTION: Insufficient educational resources on sports dentistry result in varying lecture implementations across dental schools, which cause knowledge gaps amongst students. Thus, a new interactive sports dentistry-related computer-assisted learning (CAL) module was created to facilitate dental school undergraduate students' education. This study compared the CAL module's learning effectiveness with conventional video lectures (VL) and assessed its effectiveness when used over several years at a university, and examined its validation in different university contexts, and students' perceptions. MATERIALS AND METHODS: Participants were 305 fifth-year students. Students from a university in Tokyo participated for 3 years and those from a university in Saitama for 1 year. In each year, the students were divided into two groups-CAL and VL. They studied their assigned modules in 20-min lessons. A written test was administered to determine their knowledge acquisition levels, along with a questionnaire. RESULTS: Two hundred sixty-two consenting participants were included in the statistical analysis. The CAL groups' test scores at both schools were significantly higher than the VL groups' every year (p < .001). Furthermore, test results from all years revealed no gender differences or repetition of the school years at either school. Most students at both universities evaluated the CAL module as excellent. CONCLUSION: The interactive CAL module generated consistently strong results over multiple years, during which it was used by a diverse group of students at two universities. The students highly rated the module's learning process as well as its contents.

Fabrication technique of obturator-type sports mouthguard for a patient who had undergone maxillectomy and its speech intelligibility assessment:A case report.

PURPOSE: Wearing a sports mouthguard is not only recommended in collision sports, such as American football, boxing, and rugby football, but also in low-contact sports, such as basketball, handball, and soccer. It is recommended to remove oral prosthetic devices while playing sports to avoid the risk of fracturing the device. However, players with maxillectomy must wear obturator-type prosthetic devices for speech, breathing, and deglutition even while playing sports. Therefore, there is a need for an oral appliance to prevent dental injury while playing sports without the risk of fracturing the device for players who have undergone maxillectomy.In this case, we fabricated and proposed overlay-type and obturator-type customized sports mouthguards for a patient who had undergone maxillectomy and assessments of satisfaction, speech intelligibility, nasopharyngeal closure function, and swallowing function while playing soccer. RESULTS: The patient was only satisfied with the obturator-type mouthguard, and the results of the speech intelligibility, nasopharyngeal closure function, and swallowing tests using the obturator-type mouthguard showed no differences compared to those associated with the previously used prosthetic device. CONCLUSIONS: This case may help highlight the importance of providing obturator-type mouthguards for players who have undergone maxillectomy to prevent dental injury and physical and mental discomfort.

Application of Glass Fiber and Carbon Fiber-Reinforced Thermoplastics in Face Guards.

Face guards (FGs) are protectors that allow for the rapid and safe return of athletes who are to play after sustaining traumatic facial injuries and orbital fractures. Current FGs require significant thickness to achieve sufficient shock absorption abilities. However, their weight and thickness render the FGs uncomfortable and reduce the field of vision of the athlete, thus hindering their performance. Therefore, thin and lightweight FGs are required. We fabricated FGs using commercial glass fiber-reinforced thermoplastic (GFRTP) and carbon fiber-reinforced thermoplastic (CFRTP) resins to achieve these requirements and investigated their shock absorption abilities through impact testing. The results showed that an FG composed of CFRTP is thinner and lighter than a conventional FG and has sufficient shock absorption ability. The fabrication method of an FG comprising CFRTP is similar to the conventional method. FGs composed of commercial FRTPs exhibit adequate shock absorption abilities and are thinner and lower in weight as compared to conventional FGs.

Improving the Wearing Rate of Mouthguards in the Youth Rugby Category Affects the Total Future Mouthguard Wearing Rate.

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.

The influence of temperature on sheet lamination process when fabricating mouthguard on dental thermoforming machine.

Laminated custom-made mouthguards tend to delaminate with use; this is a problem in clinical use. Insufficient bonding strength causes delamination, and bonding strength is strongly affected by heating temperature during lamination. The present study aimed to evaluate the influence of heating temperature on the sheet lamination process. Seven mouthguard sheet products were laminated together at different heating temperatures. To evaluate the bonding strength, a delamination test (n = 6) was performed, and the fracture patterns were inspected visually. To evaluate the shock absorption capability, a falling impact test (n = 5) was performed, and the specimen thicknesses were measured. All recorded values were analyzed using two-way analysis of variance and Tukey's Honest Significant Difference Test (P < 0.05). The present study confirmed that bonding strength was dependent on heating temperature: In ethylene-vinyl acetate copolymer products, the bonding strength was almost constant at 130°C and above, and it was constant at 110°C and above in polyolefin products. The thickness of every specimen decreased and, in some specimens, the shock absorption capability decreased with increasing heating temperature. The present study concludes that the heating temperature during the sheet lamination process when laminated custom-made mouthguards are fabricated may not be less than 120°C in ethylene-vinyl acetate copolymer products and 110°C in polyolefin products.

Improvement of the Shock Absorption Ability of a Face Guard by Incorporating a Glass-Fiber-Reinforced Thermoplastic and Buffering Space.

This study aimed to evaluate the shock absorption ability of trial face guards (FGs) incorporating a glass-fiber-reinforced thermoplastic (GF) and buffering space. The mechanical properties of 3.2 mm and 1.6 mm thick commercial medical splint materials (Aquaplast, AP) and experimental GF prepared from 1.6 mm thick AP and fiberglass cloth were determined by a three-point bending test. Shock absorption tests were conducted on APs with two different thicknesses and two types of experimental materials, both with a bottom material of 1.6 mm thick AP and a buffering space of 30 mm in diameter (APS) and with either (i) 1.6 mm thick AP (AP-APS) or (ii) 1.6 mm thick GF (GF-APS) covering the APS. The GF exhibited significantly higher flexural strength (64.4 MPa) and flexural modulus (7.53 GPa) than the commercial specimens. The maximum load of GF-APS was 75% that of 3.2 mm AP, which is widely used clinically. The maximum stress of the GF-APS only could not be determined as its maximum stress is below the limits of the analysis materials used (<0.5 MPa). Incorporating a GF and buffering space would enhance the shock absorption ability; thus, the shock absorption ability increased while the total thickness and weight decreased.

Interactive effect of rehydration with diluted sports drink and water gargling on salivary flow, pH, and buffering capacity during ergometer exercise in young adult volunteers.

The present study was conducted to investigate the influence of rehydration with diluted sports drink and water gargling on salivary flow, pH and buffering capacity during exercise. Nineteen participants performed a 30-min bicycle ergometer exercise at 80% of maximal heart rate while consuming a sports drink, followed by gargling with water, or no gargling, immediately after the exercise (Exp. 1). The same experiment was then conducted on 9 participants who drank 1.5-fold diluted sports drink (Exp. 2-A) and 10 who drank 2-fold diluted sports drink (Exp. 2-B). Paraffin-stimulated whole saliva samples were collected for 3 min before, during and after exercise, and salivary parameters were examined using a hand-held pH meter. Statistical significance was assessed using multi-factor ANOVA and Turkey-Kramer test (P < 0.05). The decrease in salivary pH was significantly suppressed after water gargling in Exp. 1 (P < 0.01) and Exp. 2-A (P < 0.001). Dilution of the sports drink had an interactive effect with water gargling in Exp. 2-B (P < 0.01). These results suggest that gargling with water suppresses the decrease of salivary pH resulting from sports drink rehydration during ergometer exercise, but that this effect may be lost if athletes consume sports drink that has been diluted 2-fold with water.

Novel antibacterial mouthguard material manufactured using silver-nanoparticle-embedded ethylene-vinyl acetate copolymer masterbatch.

The purpose of the present study was to develop an antibacterial mouthguard (MG) material using a masterbatch of silvernanoparticle-embedded ethylene-vinyl acetate (EVA) copolymers. In order to verify that the testing material was clinically applicable as an antibacterial MG material, we conducted an antibacterial test, a shock absorption test, and analysis of in vitro silver release. The colony-forming activity of Streptococcus sobrinus, Porphyromonas gingivalis, and Escherichia coli were significantly inhibited on the testing materials compared with the commercial EVA sheet (p<0.05). The shock absorption capability of the testing material was not significantly different from that of the commercial EVA sheet. Cumulative silver release (in pure water) from the testing materials were infinitesimal after soaking for 20 days, which implied that there could be no harm in wearing the MG during exercise. These results showed that this testing material could be clinically applicable as an antibacterial MG material.

Mouthguards and their use in sports: Report of the 1st International Sports Dentistry Workshop, 2016.

There appears to be much confusion or misinformation worldwide regarding mouthguards and their use in sports. In an effort to clarify where the international dental community stands on mouthguards and mouthguard research, the workshop looked at some important questions. The goal was to one day formulate consensus statements related to these questions, which will be based on current scientific evidence-based research, to motivate the international community of the importance of dentally fitted laminated mouthguards and the wearing of them by athletes of all sports. There are only five sports in the United States that require the use of mouthguards. If, through workshops such as this, the importance of wearing dentally fitted laminated mouthguards can be demonstrated, then more sports may require their athletes to wear them.