Forces transmitted through EVA mouthguard materials of different types and thickness

Previous studies into sporting mouthguards have been mainly attitudinal or epidemiological. The aim of the present study was to build an impact rig to measure the impact absorbed by mouthguard materials of various thicknesses. The acceleration of the pendulum of the rig was measured and used to calculate the force transmitted to the materials.
Impact tests were also performed on three commercially available mouthguard materials. Tests showed that the force transmitted through mouthguard materials was inversely related to the material thickness.
Mouthguard construction techniques with ethylene vinyl acetate (EVA) plastics should be monitored to avoid occlusal thinning especially on the incisal edges. Thinning results in reduction in the protection offered by the mouthguard.     

The effect of wearing custom-made mouthguards on the aeroacoustic properties of Japanese sibilant /s/

Abstract – Background/Aim: There have been many reports on the discomfort of speech when wearing oral appliances. Fricatives articulated in an oral cavity can be difficult to pronounce when oral appliances are worn, because the oral cavity is partially changed by their installation. Sibilant /s/, one fricative, is especially difficult to pronounce when wearing oral appliances. This study investigates the effect of the difference in the setting positions of the palatal margin of custom-made mouthguards on the aeroacoustic characteristics of sibilant /s/.Materials and methods: Eighteen subjects (11 women and seven men) participated. The palatal margin of mouthguards was set at the gingival line for nine subjects and 4 mm from the line for another nine subjects. Acoustical analyses examined the difference of the palatal margins of the mouthguards on the autocorrelation coefficient, the zero crossing count, and the spectral peaks of sibilant /s/.Results: The results showed that the zero crossing count of the waveforms and the spectral peaks of sibilant /s/ were significantly broadened and shifted toward the low-frequency range with the mouthguard whose palatal margin extended 4 mm from the gingival line than the mouthguard whose palatal margin was set at the gingival line.Conclusion: We believe that a more appropriate palatal mouthguard design for custom-made mouthguards can be made by considering the aeroacoustical effects. Our study supported the mouthguard whose palatal margin was set at the gingival line by considering the influence on pronouncing sibilant /s/. We believe that a more appropriate palatal mouthguard design for custom-made mouthguards can be made based on the balance of aeroacoustical effects and mechanical requirements.     

EVA mouthguards: how thick should they be?

Abstract – A major consideration in the performance of mouthguards is their ability to absorb energy and reduce transmitted forces when impacted. This is especially important to participants in contact sports such as hockey or football. The thickness of mouthguard materials is directly related to energy absorption and inversely related to transmitted forces when impacted. However, wearer comfort is also an important factor in their use. Thicker mouthguards are not user‐friendly. While thickness of material over incisal edges and cusps of teeth is critical, just how thick should a mouthguard be and especially in these two areas? Transmitted forces through different thicknesses of the most commonly used mouthguard material, ethylene vinyl acetate (EVA) (Shore A Hardness of 80) were compared when impacted with identical forces which were capable of damaging the oro‐facial complex. The constant impact force used in the tests was produced by a pendulum and had an energy of 4.4 joules and a velocity of 3 meters per second. Improvements in energy absorption and reductions in transmitted forces were observed with increasing thickness. However, these improvements lessened when the mouthguard material thickness was greater than 4 mm. The results show that the optimal thickness for EVA mouthguard material with a Shore A Hardness of 80 is around 4 mm. Increased thickness, while improving performance marginally, results in less wearer comfort and acceptance.     

Are all mouthguards the same and safe to use? Part 2. The influence of anterior occlusion against a direct impact on maxillary incisors

Abstract –  The purpose of this study was to clarify the influence anterior occlusion, of mouthguards, has on protecting against a direct collision to the maxillary anterior teeth. In other words, the support mandibular dentition has when wearing a mouthguard. Two types of mouthguards were used for this study, one with an appropriate anterior occlusion or a mouthguard with positive anterior occlusion (MGAO+) and another which was a single-layer mouthguard lacking the same occlusion or a mouthguard with negative anterior occlusion (MGAO−) but with the same thickness on the buccal side. The instruments used for testing were a pendulum-type impact device with two interchangeable impact objects (a steel ball and a baseball), with a plastic jaw model having artificial teeth. Four testing conditions were observed: one with the jaw open without a mouthguard (Open NoMG), the second with the jaw clenching (loaded with 30 kg weight) without a mouthguard (Clench. NoMG), the third with the jaw clenching with MGAO− (Clench. MGAO−) and the last with the jaw clenching with MGAO+ (Clench. MGAO+). The results are as follows: both types of mouthguards showed the effects in reducing the distortion of the teeth. However, the effect was significantly obvious (steel ball = about 57% shock absorption ability, baseball = about 26%) in the mouthguard with anterior occlusion or support by lower dentition through mouthguard (Clench. MGAO+) than Clench. MGAO−. Thus, the influence of anterior occlusion of mouthguards or the support of mandibular dentition through wearing a mouthguard (MGAO+) is indispensable in reducing the impact force and tooth distortion. The results of this research should further contribute to the establishment of guidelines for safer mouthguards.     

A comparison of commercially available mouthguards and a custom mouthguard

Participation in sporting events involves a risk of injury to the teeth and surrounding structures. The purpose of this study was to compare the properties of a custom mouthguard and three commercially available mouthguards. Tests included rebound upon impact as well as incisor thickness and hardness after fabrication. Results revealed that all three commercially available mouthguards exhibited greater rebound than the custom mouthguard. Rebound was related directly to the thickness of the mouthguard in the incisor region. The thickness of a mouthguard may be critical to avoiding injury to the teeth and surrounding structures.     

The influence of impact object characteristics on impact force and force absorption by mouthguard material

Abstract –  Most impact force and impact energy absorption tests for mouthguards have used a steel ball in a drop-ball or the pendulum device. However, in reality most sports-related trauma is caused by objects other than the steel ball, e.g. various sized balls, hockey puck, or bat or stick. Also, the elasticity, the velocity and the mass of the object could change the degree and the extent of injuries. In this study, we attempted to measure the impact force from actual sports equipment in order to clarify the exact mechanism of dental-related sports injuries and the protective effects of mouthguards. The present study was conducted using the pendulum impact device and load cell. Impact objects were removable. Seven mobile impact objects were selected for testing: a steel ball, baseball, softball, field hockey ball, ice hockey puck, cricket ball, and wooden baseball bat. The mouthguard material used in this study was a 3-mm-thick Drufosoft (Dreve-Dentamid GmbH, Unna, Germany), and test samples were made of the one-layer type. The peak transmitted forces without mouthguard ranged from the smallest (ice hockey stick, 46.9 kgf) to the biggest (steel ball, 481.6 kgf). The peak transmitted forces were smaller when the mouthguard was attached than without it for all impact materials but the effect was significantly influenced by the object type. The steel ball showed the biggest (62.1%) absorption ability while the wooden bat showed the second biggest (38.3%). The other balls or the puck showed from 0.6 to 6.0% absorbency. These results show that it is important to test the effectiveness of mouthguards on specific types of sports equipment. In future, we may select different materials and mouthguard designs suitable for specific sports.     

An improved mouthguard material

a modified mouthguard material which reduces transmitted forces is described. Tests showed that the inclusion of air cells in a 4 mm thick polyvinylacetate-polyethylene (EVA) copolymer reduced the effects of impacts of less than 10 KN when compared with a material of the same EVA composition and thickness. The EVA copolymer with air-inclusions is suitable for the construction of stock, mouth-formed and vacuum-formed mouthguards. The improved elastic properties of the modified mouthguard material properties of the modified mouthguard material reduced transmitted forces by 32 per cent when copared with traditional EVA mouthguard polymers of the same thickness.     

运动牙套的缓冲及能量吸收特性分析

目的:利用冲击试验测试不同厚度和材料的运动牙套缓冲及能量吸收特性.方法 :按照运动牙套的厚度和材料,将牙套分为5 组,每组6个试件.采用钟摆与力锤结合装置(摆锤)对牙套及牙列模型施加冲击能量,通过改变摆锤的释放高度而改变冲击能量的大小.应用力传感器与激光测振仪分别与数据采集和信号分析仪连接,获得锤头的人射速度、反弹速度...     

计算机辅助设计改良腭侧边缘定制护齿器对运动员配戴舒适性的影响

目的 采用数字化印模和计算机辅助设计,制作两种边缘长度的护齿器,并对上述两种护齿器在专业运动员中的使用稳定性与佩戴舒适度进行评价.方法 共纳入40名女子曲棍球职业/半职业运动员,均为恒牙列,牙周情况良好,张口度正常.检查记录口内基本情况后制取印模,灌注超硬石膏模型;使用3Shape D2000扫描仪(3Shape,丹麦...     

An evaluation of mouthguard programs in Texas high school football

Recent publications have indicated the interest in and controversy surrounding mouth protectors in sports dentistry. Mouth protection for athletes has been and continues to be dentistry's contribution to sports. Perhaps no other item of protective equipment is more effective in reducing injury to football players than a mouthguard. Although protection is no longer doubtful when a mouthguard is worn, there are still many mouthguards used that are not acceptable to the athletes in terms of comfort, durability, and speech. It is the responsibility of the dental profession to develop and dispense the best mouthguards available. From the present study it may be concluded that a properly constructed custom-made mouthguard will minimize the common complaints coaches and trainers have concerning mouthguards. It is apparent that more education about the types of mouthguards, their merits, and their availability is needed.     

Does hard insertion and space improve shock absorption ability of mouthguard?

Abstract – Mouthguards are expected to reduce sports‐related orofacial injuries. Numerous studies have been conduced to improve the shock absorption ability of mouthguards using air cells, sorbothane, metal wire, or hard material insertion. Most of these were shown to be effective; however, the result of each study has not been applied to clinical use. The aim of this study was to develop mouthguards that have sufficient prevention ability and ease of clinical application with focus on a hard insertion and space. Ethylene vinyl acetate (EVA) mouthguard blank used was Drufosoft and the acrylic resin was Biolon (Dreve‐Dentamid GMBH, Unna, Germany). Three types of mouthguard samples tested were constructed by means of a Dreve Drufomat (Type SO, Dreve‐Dentamid) air pressure machine: the first was a conventional laminated type of EVA mouthguard material; the second was a three layer type with acrylic resin inner layer (hard‐insertion); the third was the same as the second but with space that does not come into contact with tooth surfaces (hard + space). As a control, without any mouthguard condition (NOMG) was measured. A pendulum type impact testing machine with interchangeable impact object (steel ball and baseball) and dental study model (D17FE‐NC.7PS, Nissin, Tokyo, Japan) with the strain gages (KFG‐1‐120‐D171‐11N30C2: Kyowa, Tokyo, Japan) applied to teeth and the accelerometer to the dentition (AS‐A YG‐2768 100G, Kyowa) were used to measure transmitted forces. Statistical analysis (anova , P < 0.01) showed significant differences among four conditions of NOMG and three different mouthguards in both objects and sensor. About acceleration: in a steel ball which was a harder impact object, shock absorption ability of about 40% was shown with conventional EVA and hard‐insertion and about 50% with hard + space. In a baseball that was softer compared with steel ball, a decrease rate is smaller, reduction (EVA = ～4%, hard‐insertion = ～12%, hard + space = ～25%) was admitted in the similar order. A significant difference was found with all the combinations except for between EVA and hard‐insertion with steel ball (Tukey test). About distortion: both buccal and lingual, distortions had become small in order of EVA, hard‐insertion, and hard + space, too. The decrease rate is larger than acceleration, EVA = ～47%, hard‐insertion = 80% or more, and hard +space = ～98%, in steel ball. EVA = ～30%, hard‐insertion =～75%, and hard + space = ～98% in baseball. And a significant difference was found with all the combinations (Tukey test). Especially, hard + space has decreased the distortion of teeth up to several percentages. Acceleration of the maxilla and distortions of the tooth became significantly smaller when wearing any type of mouthguard, in both impact objects. But the effect of mouthguard was clearer in the distortion of the tooth and with steel ball. Considering the differences of mouthguards, the hard‐insertion and the hard + space had significantly greater buffer capacity than conventional EVA. Furthermore, hard + space shows quite high shock absorption ability in the tooth distortion. Namely, hard + space has decreased the distortion of teeth up to several percentages in both impact objects.     

Fabricating a better mouthguard. Part II: The effect of color on adaptation and fit

Abstract –  The thermoforming process involves the heating of plastic sheets to a critical temperature followed by the shaping of the heated material into a three-dimensional structure. Given that custom-fabricated mouthguards are produced using the thermoforming process, the adaptation of plastic sheets to a stone model of the dentition is likely to be affected by the ability of the mouthguard material to be heated. The purpose of this study was to establish if material color affected the adaptation and fit of custom-made mouthguards. Twelve stone models were used in this investigation. Five mouthguards were produced using each model. These mouthguards were made using clear-, white-, black-, blue- and green-colored ethyl vinyl acetate. The force required to remove the various colored mouthguards from the corresponding stone models was determined using a strain gauge housed within a specially designed apparatus. Each of the mouthguards were tested three times at two different angles of pull −45° and 90°. Statistical tests performed using the average amount of force required for mouthguard removal revealed an angle by color interaction. Post hoc analyses revealed that the mean force required to remove the clear-colored mouthguards from their respective stone models was significantly less than the force required to pull away blue-, black- and green-colored mouthguards. This difference between clear- and dark-colored mouthguards was observed at both angles tested with the exception of the black mouthguard which differed from the clear-colored mouthguard only when removed at an angle of 90°. The results of the present study indicate that by using dark-colored mouthguard material, one can achieve superior adaptation and thus produce a more firmly fitting mouthguard.     

Techniques for mouthguard fabrication

The use and efficacy of mouthguards for the prevention of traumatic athletic injuries to the teeth and oral soft tissues as well as in the prevention of concussions should indicate to the athletic community the importance of this piece of protective equipment. By comparison to other athletic equipment, mouthguards are quite inexpensive. The underlying theme is to emphasize that for maximum comfort and protection, every athlete should possess a properly fitted mouthguard fabricated exclusively for the individual by a dentist. The materials and standard techniques used for the fabrication of stock, mouth-formed, and custom-made protectors are described. The characteristics that an ideal mouthguard should possess suggest that custom-formed mouthguards are superior in quality to either the stock or mouth-formed types, although the custom-formed types are more expensive and require the services of a dentist. The development of new dental materials has provided dentists with the opportunity to explore new techniques for the fabrication of custom-made mouthguards. New techniques for photopolymerized urethane diacrylate lipguards and mouthguards have been developed as have adaptations for those athletes who wear fixed orthodontic appliances and those who are partially edentulous. Proper cleaning and storage of all types of mouthguards can prolong the length of service of these protective appliances.     

Are all mouthguards the same and safe to use? The influence of occlusal supporting mouthguards in decreasing bone distortion and fractures

Abstract –  The safety benefits of mouthguards have been demonstrated in many studies, with many authors and sports dentists strongly recommending the wearing of mouthguards. However, wearing a mouthguard with incorrect occlusion might cause a variety of problems. It comes as no surprise that a traumatic blow to the chin, while wearing an insufficient mouthguard lacking anterior contact, can result in severe distortions to the mandibular bone, and bone fractures. The aim of this study was to clarify how ineffective insufficient occlusal supporting mouthguards are and how dangerous they can be to use. Consequently, in this study, occlusal supportive areas were varied and accelerations of head and distortions of the mandible were measured using an artificial skull model and a pendulum impact device. As a result, the distortions of the mandible tended to increase as the supported area decreased. On the contrary, accelerations of the head decreased as the occlusion part decreased. Thus, a lot of impact energy was consumed in the distortion of the mandible; accordingly, it seemed that only a little destructive energy was transferred to the head. From this study, it would seem that wearing a mouthguard, which is insufficient in the occlusion, has the potential of causing a bone fracture of the mandible. Consequently, mouthguards should have proper occlusion.     

Fabricating a better mouthguard. Part I: Factors influencing mouthguard thinning

Abstract –  There is some concern regarding the amount of material thinning that occurs during the fabrication of custom-fabricated mouthguards. It is unclear if this thinning is merely a consequence of the fabrication process or related to other factors such as jaw size. Thus, the purpose of this study was to evaluate the contribution that various dimensional characteristics of the dental arch and the height of the stone model would have on mouthguard thinning. Fifteen subjects participated in this investigation. Alginate impressions from each subject were used to produce three replicas of the maxillary dentition with only the height of the base varying amongst them. The total height of the three models were 20, 25, and 30 mm. A single mouthguard was produced using each of the stone models. The material thickness of the mouthguard was assessed at the labial and occlusal surfaces. Additionally, the dimensions of the stone models were documented. Pearson product moment correlation coefficients were calculated to determine the linear relationship between material thickness and (i) the height of the stone models, (ii) the arch length and (iii) the area covered by the stone model. Statistical tests performed using the mean thickness values collected from the incisors and canines revealed a high negative correlation between the height of the stone model and material thickness ( r  = −0.82). In addition, a low to moderate positive linear correlation was noted between arch length and occlusal thickness at the molars ( r  = 0.57) and between the area of the stone model with the occlusal thickness ( r  = 0.49). The results of the present study indicate that the height of the model used to fabricate custom mouthguards should be kept as low as possible but still allow for the production of a properly fitting mouthguard.     

Attitudinal factors influencing mouthguard utilization

From the introduction of a protective mouthpiece in the sport of boxing, the evidence for the importance of this piece of athletic equipment in injury prevention has grown. Yet, despite this knowledge, only five amateur sports and one professional sport have regulations requiring the use of mouthguards. Even in the sports that require their use, compliance is not universal. Attitudes of coaches, officials, parents, and players about wearing mouthguards all influence their usage. Studies of the attitudes of these groups reveal that coaches are perceived as the individuals with the most impact on whether or not players wear mouthguards. There is reluctance among college football officials to enforce mouthguard violations that they believe are inappropriate. Parents see themselves as having responsibility in determining mouthguard use; however, their views about when and for whom mouthguards are necessary reveal a lack of complete understanding of the benefits. Resistance on the part of players stems from the physical characteristics of the mouthguard, interference with breathing and speech, and the effect on the players' image. Education on the effectiveness of properly fitted mouthguards for injury prevention, information on the risk for injury, availability of more comfortable and appealing mouthguards, and development of an approach for expanding regulations are all tools that can lead to the development of more positive attitudes and increased usage.     

Thickness and fit of mouthguards according to a vacuum‐forming process

The purpose of this study was to examine the difference in the thickness and the fit of mouthguards fabricated with a vacuum‐forming method of the mouthguard sheet material. The material used in this study was Sports Mouthguard (3.8 mm thickness). Two forming conditions were performed. In the first condition, the sheet was lowered over the working model after the vacuum was applied, and in the other trial, the sheet was lowered over the working model before the vacuum was applied. The sheets were formed using a vacuum former when the heated sheets hung 1.5 cm from the baseline. We measured the thickness and the fit of the mouthguard at the areas of the central incisor and first molar in both conditions. The difference of the thickness at the areas of the central incisor and first molar and the forming condition was analyzed by Two‐way anova . The difference of the fit according to the forming conditions was analyzed by the Mann–Whitney U test. The results showed that the thickness of the mouthguard differed at the areas of the central incisor and first molar, but the thickness of the mouthguard did not differ according to the forming conditions. The fit of the mouthguard at the central incisor and first molar was significantly different between the forming conditions (P < 0.01 and P < 0.05). These results suggested that the fit of the mouthguard was the best without any deficiency of thickness when the vacuum was applied first and then the sheet was pressed onto the working model. These results may be useful in fabricating proper mouthguards.     

Relationship between temporomandibular joint dynamics and mouthguards: feasibility of a test method

Abstract – A test system was developed establishing the feasibility of collecting biomechanical data as they relate to the use of mouthguards. Previous experimental studies have examined the physical and mechanical properties of mouthguard materials. This information has been used as a guide for establishing material standards and specifications for the fabrication of mouthguards, but it lacks the key biomechanical parameters required for a thorough mouthguard evaluation. The current study was designed to assess whether the impact force, condylar deflection, and strain superior to the temporomandibular joint region could be measured. A drop test was conducted on a cadaveric specimen to simulate loading at the chin point. To measure the force of impact, an accelerometer was attached to an impactor of known mass. High‐speed biplanar (1000 frames per second) radiographs were used to determine condylar displacement. Radio‐opaque markers were inserted into the bone at predetermined locations. Total displacement of these markers was determined in reference to anatomical landmarks. Strain gauges were attached to the mandible and skull to monitor the effects of the condyle impacting the base of the skull. Based on the data collected, forces were calculated by determining the product of the time‐based acceleration and known mass. A measurable change in force between the mouthguards and the control (no mouthguard) was demonstrated. The average condylar displacement was successfully measured and indicated as an increase in total deflection for impacts conducted with mouthguards. Quantifiable strain was measured in the region above the mandibular fossa with and without the insertion of a mouthguard at all impact conditions. However, it was determined that additional gauges would provide critical data. Key biomechanical parameters for chin‐point impacts were determined in the current study. The technique demonstrated that both displacement within the mandibular fossa and loading of the condyles occur during the impact event. Although the current study established a technique that can be used to examine the relationship between mouthguards and jaw‐joint injuries, the role, if any, mouthguards play in the reduction of injuries cannot be established until a thorough analysis is completed.     

Influence of sheet material shape on the thickness and fit of mouthguards

The aim of this study was to evaluate the influence of sheet material shape on the thickness and fit of mouthguards. Mouthguards were fabricated using ethylene vinyl acetate sheets (4.0 mm thick) and a vacuum‐forming machine. The working model was trimmed to a height of 20 mm at the incisor and 15 mm at the first molar. Three forming conditions were compared: Square sheets were fabricated while being secured by the clamping frames attached to the forming machine; round sheets were fabricated while secured by a circle tray; and square sheets were fabricated while secured by a circle tray. Each condition was defined when the sheet sagged by 15 mm below the level of the clamp. The thickness of the sheet was determined for the incisal and molar portion. Additionally, the difference in fit according to the forming conditions was analyzed. Differences in the material thickness or the fit due to forming conditions were analyzed using one‐way analysis of variance (anova ). Round sheets resulted in the thinnest mouthguard at the incisor and molar region and produced the best fit. For square sheets, no significant difference in thickness was observed between the clamping frame and circle tray methods. The fit of the mouthguard at the first molar was better when using square sheets fabricated by a circle tray than those fabricated by the clamping frame. In conclusion, when molding a mouthguard using square sheets, the thickness reduction was less and fit was better with using a circle tray, which may be clinically useful.