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.     

Thickness and fit of mouthguards according to heating methods

The purpose of this study was to examine the difference in the thickness and fit of mouthguards made by four different heating methods of the mouthguard sheet material. A Sports Mouthguard^® of 3.8‐mm thickness was used in this study. Four heating methods were performed. In one method, the sheet was heated only one side. In the other methods, one side of the sheet was heated first until the center of the sheet was displaced by 0.5 cm, 1.0 cm, and 1.5 cm from the baseline, and then turned upside down and heated. The sheets were adapted using a vacuum former when the heated sheets hung 1.5 cm from the baseline. We measured the thickness and fit of the mouthguard at the areas of the central incisor and first molar. The difference in thickness at the central incisor and first molar regions was analyzed by two‐way anova . The difference in fit with different heating methods was analyzed by one‐way anova . The results showed that the thickness of the mouthguard differed in the central incisor and first molar areas (P < 0.01 or P < 0.05), but not with the heating methods. The fit of the mouthguard at the central incisor and first molar areas was significantly different among the heating methods (P < 0.01 and P < 0.05). These results suggested that the fit of the mouthguard was superior when the heated surface of the sheet contacted the surface of the working model. This finding may help to fabricate accurate mouthguards.     

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.     

Laboratory evaluation of mouthguard material

Abstract – The aim of this study was to evaluate, in vitro , the EVA material (polyvinylacetate-polyethylene copolymer) most commonly used in the fabrication of mouthguards and thus to help understand mouthguard performance and to improve mouthguard design. The material was tested for tensile strength, elongation, hardness and water absorption using specimens and tests described by the American Society for Testing and Materials Standards. Standard EVA sheets of 1, 2, 3 and 5 mm thickness were prepared. With increase in the thickness of the material, both the ultimate tensile strength and the elongation were decreased. The hardness and water absorption were unaffected. It was concluded that, overall, the thicker 5 mm EVA material was recommended for mouthguards as it displayed the least deformation to load and performed equally as well in the tests as other thicknesses.     

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...     

Pressure‐forming method using a single‐mouthguard sheet

Background/Aim

Mouthguard thickness is important for the prevention of orofacial trauma during sports. However, it is difficult to maintain the necessary thickness after forming the mouthguard. The aim of this study was to evaluate a pressure‐forming method using a single‐mouthguard sheet.

Materials and Methods

A mouthguard sheet of 3.8 mm ethylene vinyl acetate was prepared by cutting 3 mm from the anterior margin of the sheet holder with a length of 7 mm and with the width being from the buccal cusp of the upper right first premolar to the buccal cusp of the upper left first premolar and compared with the original sheet. The sheets were pressure‐formed when the sheet was heated until the centre was displaced by 15 mm from baseline. The thickness of the mouthguard was measured at the labial surface of the central incisor, and the buccal and occlusal surfaces of the first molar. The fit of the mouthguard was examined at the right central incisor and right first molar by measuring the distance between the mouthguard and the cervical margin of the working model. Differences in the thickness and the fit of the mouthguards between the sheet conditions and the measured regions were analysed by two‐way analysis of variance.

Results

Mouthguard thickness varied among the measured regions of the central incisors and first molars (P < .01). The greatest thickness was found at the labial surface of the central incisor in mouthguards fabricated using the cut sheet (P < .01). Mouthguard fit did not differ between the two sheets.

Conclusions

The results suggest that a useful mouthguard with proper thickness and fit can be produced with the pressure‐forming method using a single‐mouthguard sheet by cutting the anterior part of the sheet.     

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.     

The effect on energy absorption of hard inserts in laminated EVA mouthguards

One of the suggestions for using laminated mouthguards is the inclusion of hard inserts to improve mouthguard performance. However, there is a paucity of published material on the use of such inserts and this study was designed to investigate this theory. Hard layers of ethylene vinyl acetate (EVA) were included in laminated mouthguard sheets which were then subject to repeated impacts with an impact rig. Hard inserts resulted in reduced energy absorption when compared with a control sheet of the same material and approximate thickness but without the hard inserts. Additionally, the further the hard inserts were located from the impact surface, the least reduction there was on energy absorption.     

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.     

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 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.     

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.     

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.     

定制牙托膜片切牙区厚度变化的影响因素

佩戴运动牙托可以缓冲外力,降低颌面部损伤的风险.运动牙托种类较多,其中个性化定制运动牙托具有较好的保护作用和较高的舒适度而备受欢迎.个性化定制运动牙托的膜片加热后可发生延展,随后发生厚度变化,尤以切牙区膜片的厚度变化更能影响其保护性能;因此,笔者就影响个性化定制运动牙托膜片切牙区的厚度变化的膜片硬度、膜片形状和膜片表面设计等膜片因素,工作模厚度和工作模摆放角度等工作模因素,加压方法,夹持托盘形状、夹持方式和夹持托盘与工作模底座的距离等夹持因素,加压时间等的研究进展作一综述.     

Comparison of forces transmitted through different EVA mouthguards

Abstract –  Athletic mouthguards have been recommended for decades with varying levels of athlete acceptance. Issues related to compliance center around the ability to breath and speak while wearing the mouthguards. Fabrication techniques have changed over time to a two-layer ethylene vinyl acetate mouthguard fabricated on a high-pressure machine. The reported ideal thickness of these mouthguards has been somewhat variable depending on the sport and anticipated level of risk. Recent research however, has identified 4 mm as the optimal thickness of EVA. In this study an acrylic dental cast was fabricated and mounted to a drop impact fixture. Mouthguards of varying ply, thickness and palatal coverage were fabricated and tested in the fixture. Strain gauges and load cells were used to evaluate the effect of ply, thickness, and palatal coverage on the ability of these mouthguards to minimize transmitted forces. The purpose of this study was to identify those variables of mouthguard construction that will minimize the overall transmitted force of impact to the anterior dentition.     

Optimal heating condition of mouthguard sheet in vacuum–pressure formation: part 2 Olefin‐based thermoplastic elastomer

The purposes of this study were to clarify the suitable heating conditions during vacuum–pressure formation of olefin copolymer sheets and to examine the sheet temperature at molding and the thickness of the molded mouthguard. Mouthguards were fabricated using 4.0‐mm‐thick olefin copolymer sheets utilizing a vacuum–pressure forming device, and then, 10 s of vacuum forming and 2 min of compression molding were applied. Three heating conditions were investigated. They were, defined by the degree of sagging observed at the center of the softened sheet (10, 15, or 20 mm lower than the clamp (H‐10, H‐15, or H‐20, respectively)). The working model was trimmed to the height of 20 mm at the maxillary central incisor and 15 mm at the mesiobuccal cusp of the maxillary first molar. The temperature on both the directly heated and the non‐heated surfaces of the mouthguard sheet was measured by the radiation thermometer for each condition. The thickness of mouthguard sheets after fabrication was determined for the incisal portion (incisal edge and labial surface) and molar portion (cusp and buccal surface), and dimensional measurements were obtained using a measuring device. Differences in the thickness due to the heating condition of the sheets were analyzed by one‐way analysis of variance and Bonferroni's multiple comparison tests. The temperature difference between the heated and non‐heated surfaces was highest under H‐10. Sheet temperature under H‐15 and H‐20 was almost the same. The thickness differences were noted at incisal edge, cusp, and buccal surface, and H‐15 was the greatest. This study demonstrated that heating of the sheet resulting in sag of 15 mm or more was necessary for sufficient softening of the sheet and that the mouthguard thickness decreased with increased sag. In conclusion, sag of 15 mm can be recommended as a good indicator of appropriate molding timing for this material.     

Oro-facial injuries and mouthguard use in elite female field hockey players

Abstract –  The objectives of this study were to assess the prevalence of oro-facial injuries, frequency of mouthguard use and players' attitudes towards the use of mouthguards among elite English female field hockey players. All 140 players of the English Hockey Association female Premiere League were asked to complete a questionnaire. Main outcome measures were prevalence of oro-facial injuries, frequency of wearing of mouthguards and attitudes to mouthguard wearing. One hundred and ten completed questionnaires were returned (79% response rate). Facial injuries were common. Nineteen percent had sustained dental injury. Five percent of the respondents had at least one tooth avulsed. Eighty-eight percent of the players said that they owned a mouthguard. Mouthguards were worn regularly during matches by 69% but were used less frequently during training. Six percent thought that mouthguards were ineffective. Eighteen percent of the subjects refused to play if they did not have their mouthguard. Sixty-nine percent of the subjects felt that the mouthguards should be worn compulsorily at all times during the game. The following were finally concluded from the study: oro-facial injuries were commonly reported; 88% of the players possessed a mouthguard; and mouthguards were worn regularly during matches by 69% but were used less frequently during training.     

Nigerian dentists' knowledge and attitudes towards mouthguard protection

Abstract –  The objective of this study was to assess the knowledge and attitudes of Nigerian dentists towards mouthguard protection. A pre-tested 15-item, one-page questionnaire was distributed to 185 dentists practising in different parts of the country with government hospitals or private establishments, by 'hand-delivery' system. Filled and returned forms were 170 (response rate of 92%). The period of the survey was between April and August 2003. Dental graduates from the different dental schools in the country responded to this survey. About 49% of the respondents indicated having only classroom lectures on mouthguards during their undergraduate trainings, 11% said they had some laboratory sessions in addition while no form of education on mouthguards was received by 40%. About 82% had never recommended mouthguard protection for athletic patients, and the major reason was no formal training in the subject. Only 58.5% were familiar with the different types of mouthguards, 75.9% would not be able to supervise or fabricate mouthguards and 50.6% would prefer custom-made mouthguard for their athletic patients. About 84% felt the current training on mouthguards in Nigerian dental schools is inadequate. Over 98% agreed that mouthguard usage in contact sports should be encouraged with the involvement of the dentists. The knowledge and attitudes of the respondents towards mouthguard protection did not vary significantly across years of postqualification from dental schools as well as the professional status of the dentists ( P  > 0.05). Although Nigerian dentists support mouthguard protection in contact sports and want to be involved in the provision of mouthguards for athletes, their knowledge of the protective device is inadequate. There is need for attention to be given to this subject in the undergraduate curricula of our dental schools.