A three-dimensional finite element analysis of the sports mouthguard

Methods and applications of finite element analysis in dental trauma research: A scoping review

Finite Element Analysis (FEA) is vital for understanding dental traumatology (DT) biomechanics, aiding diagnosis, treatment planning, and outcome prediction. This review explores FEA applications in DT research, evaluates their quality and outcomes, and assesses methodological aspects. Accordingly, recommendations for future researchers are provided. The study adhered to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for scoping reviews and registered in Open Science framework. A comprehensive search using relevant text-words and MeSH terms was performed in established databases. The inclusion criteria encompassed all Finite element analysis (FEA)-based Dental traumatology (DT) studies without language or publication year restrictions. Risk of bias was assessed with the Risk of bias tool for the use of finite element analysis in dentistry (ROBFEAD) tool. Forty-six studies published from 2001 to 2023 were included in the qualitative synthesis. The studies were categorized into five domains and six subdomains based on objectives. Maxillary central incisors and surrounding structures were commonly modelled (n = 27). Most studies utilized Computed tomography (CT), Cone Beam CT, or micro CT. Traumatic injury forces ranged from 100 N to 2000 N, and occlusal forces ranged from 150 N to 350 N. All studies were rated as high risk of bias. Fory-six studies were categorized, with most focusing on stress distribution and fracture patterns in dento-alveolar structures under various conditions, while few assessed displacements. Methodological quality lacked robustness in model development and substructure properties. Future studies should address these limitations and enhance reporting practices.

The production and materials of mouthguards: Conventional vs additive manufacturing - A systematic review

This investigation presents a critical analysis of mouthguard production, focusing on the evaluation of conventional vs additive manufacturing methods, the materials involved, and aspects such as their failure and prevention. It also summarizes the current trends, perspectives, and the main limitations. It is shown that some of the shortcomings can be solved by implementing additive manufacturing technologies, which are systematically reviewed in this research. Due to the specific materials used to produce mouthguards, there are certain additive manufacturing technologies that dominate and a wide variety of raw materials. The costs vary depending on the technology.

Design of Customized Mouthguards with Superior Protection Using Digital-Based Technologies and Impact Tests

BACKGROUND

In contact sports, an impact on the jaw can generate destructive stress on the tooth-bone system. Mouthguards can be beneficial in reducing the injury risk by changing the dynamics of the trauma. The material properties of mouthguards and their geometrical/structural attributes influence their protective performance. Custom-made mouthguards are the gold standard, and different configurations have been proposed to improve their protection and comfort. However, the effects of different design variables on the performance of customized mouthguards are not well understood.

RESULTS

Herein, we developed a reliable finite element model to analyze contributing factors to the design of custom-made mouthguards. Accordingly, we evaluated the isolated and combined effect of layers' stiffness, thickness, and space inclusion on the protective capability of customized mouthguards. Our simulations revealed that a harder frontal region could distribute load and absorb impact energy through bending if optimally combined with a space inclusion. Moreover, a softer layer could enlarge the time of impact and absorb its energy by compression. We also showed that mouthguards present similar protection with either permanently bonded or mechanically interlocked components. We 3D-printed different mouthguards with commercial resins and performed impact tests to experimentally validate our simulation findings. The impact tests on the fabricated mouthguards used in this work revealed that significantly higher dental protection could be achieved with 3D-printed configurations than conventionally fabricated customized mouthguards. In particular, the strain on the impacted incisor was attenuated around 50% more with a 3D-printed mouthguard incorporating a hard insert and space in the frontal region than a conventional Playsafe® Heavypro mouthguard.

CONCLUSIONS

The protective performance of a mouthguard could be maximized by optimizing its structural and material properties to reduce the risk of sport-related dental injuries. Combining finite element simulations, additive manufacturing, and impact tests provides an efficient workflow for developing functional mouthguards with higher protectiveness and athlete comfort. We envision the future with 3d-printed custom-mouthguards presenting distinct attributes in different regions that are personalized by the user based on the sport and associated harshness of the impact incidences.

Comparison of shock absorption capacities of three types of mouthguards: A comparative in vitro study

BACKGROUND/AIM

3D printing processes can be used to manufacture custom-made mouthguards for sports activities. Few studies have compared the impact performance of industrial-created mouthguards with that of custom-made mouthguards manufactured by thermoforming or 3D printing. The objective of this in vitro study was to compare the shock absorption capacities of custom-made mouthguards manufactured by 3D printing with industrial mouthguards and thermoformed ethylene vinyl acetate (EVA) mouthguards.

MATERIALS AND METHODS

For each type of mouthguard, eight samples were produced. 3D-printed mouthguards were manufactured using digital light processing technology. Each mouthguard was subjected to an impact performance test defined by the standard AFNOR XP S72-427, which evaluate maximum deceleration and force transmitted during impact. The thickness of each mouthguard before and after a series of five impacts was measured at the impacted inter-incisal area.

RESULTS

The mean maximum decelerations during impact ranged from 129 to 189 g for industrial mouthguards, 287 to 425 g for thermoformed EVA mouthguards, and 277 to 302 g for 3D-printed mouthguards. The mean reduction in mouthguard thickness at the impact zone after five tests was 1.2 mm for industrial mouthguards, 0.6 mm for 3D-printed mouthguards, and 2.2 mm for thermoformed EVA mouthguards.

CONCLUSIONS

Custom-made 3D printed mouthguards showed slightly better shock absorption ability than thermoformed mouthguards with respect to the indicator proposed in XP S72-427. They seemed to combine the practical advantages of thermoformed mouthguards in sports with better shock absorption capacity and lower cost. Furthermore, they had the least thickness variation during the test, and their shock absorption capacity was the least affected by repeated mechanical tests. Other types of 3D-printing resin materials that will become available must continue to be tested for shock absorption to provide the best protection to users at low cost.

Sports mouthguard overview: Materials, fabrication techniques, existing standards, and future research needs

Sports mouthguards are proven devices that reduce both the probability of and damage to orofacial tissues. While commonly used, clinicians may be unaware of the different sports mouthguard materials, proposed fabrication techniques, design recommendations, and newer digital fabrication methods. An overview of existing sports mouthguard standards is presented. It identifies that identify that the present requirements, while historically chosen in good faith, appear to be arbitrarily selected and not from clinical evidence-based derived data. In addition, identified sports mouthguard heterogeneous testing and data acquisition methods distinguishes that little possibility is afforded for the correlation of results. Furthermore, updated evidence with concussion prevention and/or alleviation is presented with evidence provided by sports mouthguard imbedded technology. The need for continued research is stressed to provide evidence-based data for concussion alleviation/prevention, digital fabrication methods and materials, and clinically based information for the revision of existing standards.

Evaluation of Mechanical Properties of 3D-Printed Polymeric Materials for Possible Application in Mouthguards

Custom mouthguards are used in various sports disciplines as a protection for teeth, temporomandibular joints, and soft tissues of the oral cavity from impact forces. The purpose of this research was to evaluate the mechanical properties of flexible polymeric 3D-printable materials and to select a material with the most favourable physical properties for making intraoral protectors. Four 3D-printable polymeric materials were selected for the evaluation: IMPRIMO LC IBT (Scheu-Dental, Iserlohn, Germany), Keyortho IBT (EnvisionTEC, Gladbeck, Germany), IBT (Formlabs, Somerville, MA, USA), and Ortho IBT (NextDent, Utrecht, Netherlands). A total of 176 samples (44 from each material) was 3D-printed using the stereolitography (SLA) technique. Tensile strength, flexural strength, notch-toughness, Shore hardness, sorption, and solubility tests were conducted. The materials were compared using a series of analyses of variance (one-way ANOVA) with Bonferroni post hoc tests. Statistical analyses were performed with the use of IBM SPSS Statistics 28.0.0 software (IBM, New York, NY, USA). Each material was assigned a score from 1 to 4 depending on the individual test results, and tests were given indexes according to the significance of the parameter in the mouthguard protective function. The number of points obtained by each material in each test was then multiplied by the test index, and the results were tabulated. The material with the highest result among the ones studied-most suitable for the application in mouthguard fabrication-was Keyortho IBT from EnvisionTEC.

Prioritizing model trimming to prevent thinning during mouthguard thermoforming: Influence of increased height associated with an acute model angle

BACKGROUND/AIM

The shape of the working model is one of the major factors affecting the thickness of thermoformed mouthguards. The aim of this study was to clarify the priority of model trimming to prevent thinning during mouthguard thermoforming.

MATERIALS AND METHODS

Mouthguards were thermoformed using 4.0 mm thick ethylene-vinyl-acetate sheets and a vacuum forming machine. Working models were trimmed so that the angles of the labial surface to the model base were 100°, 90°, and 80°. The posterior height was unified to 30 mm, and the anterior heights were 30 mm (A100-L), 35 mm (A90-M), and 40 mm (A80-H), respectively. When the sheet temperature reached 100°C, vacuum forming was performed. Six specimens were formed for each condition. Mouthguard thickness (incisal edge, labial surface, cusp, and buccal surface) was measured using a specialized caliper accurate to 0.1 mm. Differences in thickness reduction rate due to model shapes were analyzed by one-way ANOVA and Bonferroni's multiple comparison tests.

RESULTS

At the incisal edge, there were no significant differences in the reduction rate of the thickness of the mouthguard according to model shapes. On the labial surface, cusp, and buccal surface, the smaller the model angle, the smaller the reduction rate of thickness, and significant differences were observed between A100-L and A80-H, and A90-M and A80-H. On the labial and buccal surfaces, A80-H was more than 7.1% thicker compared with A100-L and more than 5.6% thicker compared with A90-M, and the thickness reduction rate was reduced when the model was trimmed to an acute angle. At the cusp, A80-H was more than 4.3% thicker than A100-L and A90-M.

CONCLUSIONS

It is useful to trim the model at an acute angle in order to prevent thinning during mouthguard thermoforming, even if the anterior height of the model is increased.

In vitro study of how the undercut amount on the model labial side affects the reduction rate of laminated mouthguard thickness

BACKGROUND/AIM

An undercut on the model's labial side affects the mouthguard thickness. The aim of this study was to investigate how the undercut amount on the model's labial side affects the reduction rate of laminated mouthguard thickness.

MATERIALS AND METHODS

Mouthguards were thermoformed using 3.0-mm-thick ethylene-vinyl-acetate sheets for the first and second laminates and a pressure molding machine. Working models were three hard plaster models trimmed so that the undercut amount on the model's labial side was 0°, 10°, and 20° (U0, U10, and U20). A specialized caliper was used to measure the thickness of the incisal, labial surface, and buccal surface of the first layer and the laminated mouthguards. Thickness reduction rate of the first layer or laminated mouthguard due to the model undercut amount were analyzed using one-way ANOVA. Additionally, in each model, the difference in the thickness reduction rate between the first layer and the laminated mouthguard were analyzed by Student's t-test or Welch's test.

RESULTS

Differences in the thickness reduction rate depending on the model's undercut amount showed the same tendency between the first layer and the laminated mouthguard. Significant differences were observed between U0 and U10 as well as U0 and U20 at the incisal edge, and these were observed among all models on the labial and buccal surfaces (p < .01). On the labial surface, the rate of decrease in the laminated mouthguard thickness compared to U0 was approximately 10.4% larger for U10 and approximately 14.9% larger for U20 (p < .01). The thickness reduction rate of the laminated mouthguard was significantly smaller than that of the first layer, which was observed in all models at the incisal edge and in U10 and U20 on the labial surface (p < .01).

CONCLUSIONS

The presence of a 10° or 20° undercut on the model's labial side increases the thickness reduction rate on the labial side of the laminated mouthguard by approximately 10% or 15%.

Effect of sheet extrusion direction on laminated mouthguard thickness: An in vitro study

BACKGROUND/AIM

The thermal shrinkage that occurs when the extrusion molding sheet is heated affects the mouthguard thickness. The aim of this study was to investigate the effect of sheet extrusion direction on laminated mouthguard thickness.

MATERIALS AND METHODS

Mouthguards were pressure formed using the extruded sheet and a plaster model. For the first layer, a 3.0-mm-thick sheet was used. For the second layer, a 2.0- or 3.0-mm-thick sheet was used. In each of the first (F) and second (S) layers, the sheet extrusion direction was either vertical (V; FV, SV) or parallel (P; FP, SP) to the model midline. Thickness differences depending on the extrusion direction of the first layer was analyzed by Student's t-test. Differences in the laminated mouthguard thickness depending on the extrusion direction of the first or second layer and the sheet thickness of the second layer were analyzed by three-way ANOVA.

RESULTS

The first layer was significantly thicker in FV by about 0.20 mm than in FP at the incisal edge, labial surface, and cusp (p < .01). No significant difference was observed between SV and SP in the laminated mouthguard. However, at the incisal edge, labial surface, and cusp of the laminated mouthguard, FV were significantly thicker by 0.17 mm or more than FP under all laminating conditions (p < .01). A 3.0-mm-thick laminating condition was thicker than a 2.0-mm-thick laminating condition by 0.47 mm or more at the incisal edge, labial, and buccal surfaces, and by 0.34 mm or more at the cusp.

CONCLUSIONS

The laminated mouthguard thickness can be secured by molding the first-layer sheet so that the extrusion direction is vertical to the model midline. In the second layer, the extrusion direction did not affect the laminated mouthguard thickness, and a thicker sheet material should be used.

Stress Concentration of Hybrid Occlusal Splint-Mouthguard during a Simulated Maxillofacial Traumatic Impact: 3D-FEA

Mouthguards (MG) are protective devices that can reduce the risks of facial trauma. However, many athletes do not use them. Additionally, MG wear with coincidental parafunctional activity has not been considered. The aim of this study was to evaluate the stress distribution as a consequence of a direct impact comparing a conventional MG with a novel hybrid appliance (HMG). Using computer-aided design (CAD) software, a human skull was modeled with the teeth inserted into their respective alveolus. The models were divided according to the MG type (conventional or hybrid). The geometries were exported to the computer-aided engineering (CAE) software and the materials were considered isotropic. Fixation was defined at the base of the maxilla. The load was applied using a hockey puck. The total deformation (mm) and the von Mises stress (MPa) results were obtained for the MGs (conventional and hybrid), upper teeth, lower teeth, and maxillary bone. Despite the presence of an MG, it is still possible to observe generated stress in all structures. However, the hybrid design was more efficient than the conventional design in reducing the displacement during the impact and consequently the stress on the upper teeth, lower teeth, and maxillary bone. Higher stress magnitude was more concentrated at the inner portion of the hybrid design than the conventional device. The HMG appliance decreased the stress concentration in the teeth and in the bone, limiting the areas susceptible to injuries to the regions directly impacted by the hockey puck. Although the novel HMG may mitigate injury, some stress will still result, and any possible injury should be evaluated by a dental professional.

Effective thermoforming method for maintaining mouthguard thickness with a circular sheet using a circular frame

BACKGROUND/AIM

Mouthguard thickness is important to prevent oral and facial trauma during sports. The aim of this study was to establish an effective thermoforming method for maintaining mouthguard thickness with a circular sheet using a circular frame.

MATERIALS AND METHODS

Mouthguards were thermoformed using 4.0-mm-thick ethylene vinyl acetate sheets and a vacuum forming machine. Each sheet was pinched at the top and bottom and stabilized by a circular frame. Two heating conditions were compared: (1) condition N, where the sheet was formed when it sagged 10 mm below the level of the sheet frame at the top of the post, and (2) condition L, where the sheet frame was lowered 50 mm below the ordinary level and heated, and the sheet was formed when it sagged 10 mm. In each heating method, two forming conditions were compared: (1) when the sheet softened, the sheet frame was lowered and formed (condition C; N-C, L-C), and (2) after the sheet frame was lowered, the model was moved forward 20 mm and then formed (condition MP; N-MP, L-MP). Six mouthguards were fabricated for each condition. Thickness differences due to heating conditions and forming conditions were analyzed by the two-way ANOVA and Bonferroni's multiple comparison test.

RESULTS

At the incisal edge and at the labial and buccal surfaces, significant differences were observed among all conditions, and the thicknesses were in the order N-C < L-C < N-MP <L-MP. At the cusp, significant differences were not observed depending on the heating conditions.

CONCLUSIONS

The thermoforming method with a circular sheet using a circular frame did not maintain a sufficient thickness only by the method of moving the model position just before formation. However, the results suggest that a single-layer mouthguard with a labial thickness of 3 mm or more could be fabricated by applying the method of lowering the sheet frame and heating the sheet.

Examination of thermoforming techniques to secure mouthguard thickness of the labial and buccal sides with a single sheet: An in vitro study

BACKGROUND/AIM

Mouthguards must have an appropriate thickness to prevent oral trauma during sports. The aim of this study was to establish a thermoforming technique to secure the labial and buccal thicknesses of the mouthguard with a single sheet.

MATERIALS AND METHODS

Mouthguards were thermoformed using 4.0-mm thick sheets manufactured by extrusion molding, a plaster model, and a vacuum forming machine. Two sheet installation conditions were compared: the sheet extrusion direction was either parallel (P) or vertical (V) to the model's centerline. In each extrusion direction, two forming conditions were compared: (1) the sheet was formed when it sagged 15-mm below the sheet frame at the top of the post (control group; C-P, C-V); and (2) the sheet frame was lowered 50-mm below the ordinary level and heated, the frame was lowered when it sagged 15-mm, and the model was moved forward 20-mm before formation (experimental group; E-P, E-V). Difference in thickness (incisal edge, labial surface, cusp, and buccal surface) due to sheet extrusion direction and forming conditions were analyzed by two-way ANOVA and the Bonferroni method.

RESULTS

At all measurement sites, a significant difference in thickness depending on the sheet extrusion direction was observed in the experimental group (p < .01), but not in the control group. Difference in thickness depending on the forming condition was observed at all measurement sites, and the thickness was in the order C-P, C-V < E-P < E-V. Thicknesses of E-P and E-V were 3.01 ± 0.03 mm and 3.25 ± 0.02 mm on the labial surface, and 2.81 ± 0.02 mm and 3.02 ± 0.02 mm on the buccal surface.

CONCLUSIONS

It was possible to obtain 3 mm or more thickness on the labial and buccal sides with a single sheet by adjusting the sheet extrusion direction and the heating method of the sheet, and by applying the thermoforming method where the model is moved forward just before formation.

Biomechanical Behavior Evaluation of a Novel Hybrid Occlusal Splint-Mouthguard for Contact Sports: 3D-FEA

Background: Orofacial injuries are common occurrences during contact sports activities. However, there is an absence of data regarding the performance of hybrid occlusal splint mouthguards (HMG), especially during compressive loading. This study amid to evaluate the biomechanical effects of wearing a conventional custom mouthguard (MG) or the HMG on the teeth, bone, and the device itself. Methods: To evaluate the total deformation and stress concentration, a skull model was selected and duplicated to receive two different designs of mouthguard device: one model received a MG with 4-mm thickness and the other received a novel HMG with the same thickness. Both models were subdivided into finite elements. The frictionless contacts were used, and a nonlinear analysis was performed simulating the compressive loading in occlusion. Results: The results were presented in von-Mises stress maps (MPa) and total deformation (mm). A higher stress concentration in teeth was observed for the model with the conventional MG, while the HMG design displayed a promising mechanical response with lower stress magnitude. The HMG design displayed a higher magnitude of stress on its occlusal portion (7.05 MPa) than the MG design (6.19 MPa). Conclusion: The hybrid mouthguard (HMG) reduced (1) jaw displacement during chewing and (2) the generated stresses in maxillary and mandibular teeth.

Modeling the Contact Interaction of a Pair of Antagonist Teeth through Individual Protective Mouthguards of Different Geometric Configuration

This study carried out modeling of the contact between a pair of antagonist teeth with/without individual mouthguards with different geometric configurations. Comparisons of the stress–strain state of teeth interacting through a multilayer mouthguard EVA and multilayer mouthguards with an A-silicon interlayer were performed. The influence of the intermediate layer geometry of A-silicone in a multilayer mouthguard with an A-silicon interlayer on the stress–strain state of the human dentition was considered. The teeth geometry was obtained by computed tomography data and patient dental impressions. The contact 2D problem had a constant thickness, frictional contact deformation, and large deformations in the mouthguard. The strain–stress analysis of the biomechanical model was performed by elastoplastic stress–strain theory. Four geometric configurations of the mouthguard were considered within a wide range of functional loads varied from 50 to 300 N. The stress–strain distributions in a teeth pair during contact interaction at different levels of the physiological loads were obtained. The dependences of the maximum level of stress intensity and the plastic deformation intensity were established, and the contact parameters near the occlusion zone were considered. It was found that when using a multilayer mouthguard with an A-silicone interlayer, there is a significant decrease in the stress intensity level in the hard tissues of the teeth, more than eight and four times for the teeth of the upper and lower teeth, respectively.

The Effectiveness of Dental Protection and the Material Arrangement in Custom-Made Mouthguards

Experimental research studies have shown that wearing a mouthguard (MG) is an effective way to prevent tooth or maxillofacial trauma. However, there is a lack of scientific information regarding how the material arrangement within the mouthguard can modify its mechanical response during an impact. Hence, this study aimed to evaluate the influence of material arrangement within custom-made mouthguards on stress transmitted to anterior teeth, bone, and soft tissue after impact. Four 3D finite element models of a human maxilla were reconstructed based on the CBCT of a young patient and analyzed according to the presence or absence of a mouthguard and the type of material arrangement within those with a mouthguard: model NMG with no mouthguard; model CMG representing the conventional arrangement with a single 4 mm-thick ethylene-vinyl acetate (EVA) foil; model FMG presenting layer arrangement with two 1 mm-thick foils of EVA in the outer shell and one 2 mm-thick foil of EVA foam in the core; model HMG presenting a 1 mm-thick compact inner and outer shell of EVA and a 2 mm wide air-filled zone in the core. Linear quasi-static analysis and frontal load were used to simulate an impact with an energy of 4.4 J. Isotropic linear elastic properties were assumed for the bone and teeth but not for the mouthguard protection and oral soft tissues. The results were evaluated and compared in terms of displacement, stretches, and stresses. All the mouthguards analyzed reduced the risk of injury to teeth and bone, reducing the displacement and stress of these structures. However, the implementation of a honeycomb structured layer allowed more significant displacement and deformation of the mouthguard’s external layer, thus promoting higher protection of the anatomic structures, namely the root dentin and the bone tissue. Nevertheless, the results also indicate that improving the mouthguard flexibility might increase the soft tissue injuries.

Effects on the thickness of single-layer mouthguards with different model positions on the forming table and different sheet frame shapes for the forming device

BACKGROUND/AIM

Effectiveness and safety of mouthguards are greatly affected by their thickness. The aim of this study was to clarify the influence of the frame shape of the forming device on how the model position on the forming table affects the anterior and posterior mouthguard thickness.

MATERIALS AND METHODS

Mouthguards were thermoformed using 4.0-mm-thick ethylene-vinyl-acetate sheets and a vacuum forming device. Square sheets were fixed with the square frame of the forming device. Circular sheets were fixed to the forming device with a circular frame. The model was placed with its anterior rim positioned 40, 30, 20, or 10 mm from the front of the forming table. The model position was marked on the forming table so that it was constant under each condition. Six mouthguards were fabricated for each condition. Mouthguard thicknesses of the incisal edge, labial and buccal surfaces, and the cusp were measured. Differences in the rate of thickness reduction due to frame shapes and model positions were analyzed by two-way ANOVA.

RESULTS

Difference in the thickness reduction rate depending on the frame shape was observed on the labial and buccal surfaces, and it was significantly greater with the circular frame than with the square frame (p < .01). In the anterior region, the thickness reduction rate tended to increase as the model position was moved toward the front of the forming table. The thickness reduction rate of the posterior portion was lowest when the model's molar was positioned at the center of the forming table.

CONCLUSIONS

The labial thickness of the mouthguard was not affected by the frame shape if the distance from the model to the frame was larger than the model height. However, the buccal thickness was thinner with the circular frame than with the square frame regardless of the model position.

Effect on thickness of a single-layer mouthguard of positional relationship between suction port of the vacuum forming device and the model

BACKGROUND/AIM

Wearing a mouthguard reduces the risk of sport-related injuries, but the thickness has a large effect on its efficacy and safety. The aim of this study was to investigate the effect on the thickness of a single-layer mouthguard of the positional relationship between the suction port of the vacuum forming device and the model.

MATERIALS AND METHODS

Ethylene-vinyl-acetate sheets of 4.0-mm-thickness and a vacuum forming machine were used. Two hard plaster models were prepared: Model A was 25-mm at the anterior teeth and 20-mm at the molar, and model B was trimmed so the bucco-lingual width was half that of model A. Three model positions on the forming table were examined: (a) P20, where the model anterior rim was located in front of the suction port, (b) P30, where the model anterior rim and front edge of the suction port were close, and (c) P43, where the model anterior rim and palatal rim were located on the suction port. Six mouthguards were fabricated for each condition. Thickness differences due to model form and model position were analyzed.

RESULTS

Thickness differences due to model form were observed at the incisal edge and labial surface, and model A was significantly thicker than model B in P43 (P<.01). The thickness of the incisal edge and labial surface was significantly greatest in P43 for model A, but in P30 for model B.

CONCLUSIONS

The effect of the model position on the forming table on suppressing the labial thickness reduction of the mouthguard depended on the bucco-lingual width of the model. It is important to position the model anterior rim away from the sheet frame if the bucco-lingual width of the model is large and to place the model anterior rim in front of the suction port if the width is small.

Mouthguard Use Effect on the Biomechanical Response of an Ankylosed Maxillary Central Incisor during a Traumatic Impact: A 3-Dimensional Finite Element Analysis

(1) Background: Trauma is a very common experience in contact sports; however, there is an absence of data regarding the effect of athletes wearing mouthguards (MG) associated with ankylosed maxillary central incisor during a traumatic impact. (2) Methods: To evaluate the stress distribution in the bone and teeth in this situation, models of maxillary central incisor were created containing cortical bone, trabecular bone, soft tissue, root dentin, enamel, periodontal ligament, and antagonist teeth were modeled. One model received a MG with 4-mm thickness. Both models were subdivided into finite elements. The frictionless contacts were used and a nonlinear dynamic impact analysis was performed in which a rigid object hit the model at 1 m·s^-1. For each model, an ankylosed periodontal ligament was simulated totaling 4 different situations. The results were presented in von-Mises stress maps. (3) Results: A higher stress concentration in teeth and bone was observed for the model without a MG and with ankylosed tooth (19.5 and 37.3 MPa, respectively); the most promising mechanical response was calculated for patients with healthy periodontal ligament and MG in position (1.8 and 7.8 MPa, respectively). (4) Conclusions: The MG's use is beneficial for healthy and ankylosed teeth, since it acts by dampening the generated stresses in bone, dentin, enamel and periodontal ligament. However, patients with ankylosed tooth are more prone to root fracture even when the MG is in position compared to a healthy tooth.

Effect of acute angle model on mouthguard thickness with the thermoforming method and moving the model position just before fabrication

BACKGROUND/AIM

The effectiveness and safety of mouthguards are affected by their thickness. The aim of this study was to investigate the effect of an acute angle model on the mouthguard thickness with the thermoforming method in which the model position was moved just before fabrication.

MATERIALS AND METHODS

Mouthguards were thermoformed using 4.0 mm thick ethylene vinyl acetate sheets and a vacuum forming machine. Three hard plaster models were prepared: 1) the angle of the labial surface to the model base was 90°, and the anterior height was 25 mm (model A); 2) the angle was 90°, and the anterior height was 30 mm (model B); and 3) the angle was 80°, and the anterior height was 30 mm (model C). The sheet was softened until it sagged 15 mm, after which the sheet frame was lowered to cover the model. The model was then pushed from behind to move it forward, and the vacuum was switched on (MP). The model was moved 20 mm whereas a control model was not moved. Mouthguard thickness was measured using a specialized caliper. The differences in mouthguard thicknesses due to model forms and forming conditions were analyzed by two-way ANOVA and Bonferroni's multiple comparison tests.

RESULTS

The MP tended to be thicker than the control in all models. In the controls, model C was significantly thicker than models A and B at the labial and buccal surfaces. In MP, model A was significantly thicker than models B and C on the labial surface. On the labial and buccal surfaces in MP, model C was significantly thicker than model B.

CONCLUSIONS

This study suggested that in the thermoforming method in which the model position was moved just before fabrication, reducing the height was more effective than changing the angle of the model to ensure the appropriate thickness.

Fabrication method to maintain mouthguard thickness regardless of the model angle

BACKGROUND/AIM

The safety and effectiveness of mouthguards depend on the sheet material and thickness. The aim of this study was to investigate the fabrication method for a mouthguard with appropriate thickness using a single sheet regardless of the model angle.

MATERIALS AND METHODS

Mouthguards were thermoformed using 4.0 mm thick ethylene vinyl acetate sheets and a vacuum forming machine. The working models were three hard plaster models trimmed so that the angle of the anterior teeth to the model base was 90°, 100°, and 110°. The model position was 40 mm from the front of the forming unit. The sheet was softened until it sagged 15 mm, after which the sheet frame was lowered to cover the model. Next, the vacuum was turned on and held for 30 seconds for the control. Under the forming conditions in which the model position (MP) was moved, after the model was covered with the sheet, a scissors handle was positioned at the rear of the model and used to push it forward 20 mm, and then, the vacuum switch was turned on for 30 seconds. Six specimens were formed for each condition. Mouthguard thickness after formation was measured using a specialized caliper. The differences in mouthguard thickness due to forming conditions and model angle were analyzed.

RESULTS

The MP was significantly thicker than the control in each model (P < .01). The mouthguard thickness tended to decrease as the model angle increased. The average thickness of the labial surface in the MP was 3 mm or more and was not affected by the model angle.

CONCLUSIONS

This study suggested that the fabrication method in which moving the model forward by 20 mm just before formation could produce a mouthguard with approximately 3 mm thickness on the labial side with a single sheet regardless of the model angle.

Establishment and Simulation of 3D Geometric Models of Mini-Pig and Sheep Knee Joints Using Finite Element Analysis

Background

Our objective was to establish and compare three-dimensional models of knee joints of mini-pigs and sheep, the 2 most commonly used animal models of osteoarthritis.

Material/Methods

Three-dimensional geometric models of knee joints were used to assess their biomechanical properties by analysis of the three-dimensional finite element stress load for flexion at 30° and 60°.

Results

Analysis of multiple tissues indicated that the sheep knee had greater stress peaks than the mini-pig knee at 30° flexion (range: 12.5 to 30.4 Mpa for sheep vs. 11.1 to 20.2 Mpa for mini-pig) and at 60° flexion (range: 17.9 to 43.5 Mpa for sheep vs. 15.9 to 28.9 Mpa for mini-pig). In addition, there was uneven distribution of stress loads in the surrounding ligaments during flexion.

Conclusions

Our three-dimensional finite element analysis indicated that the mini-pig knee joint had stress values and changes of cartilage, meniscus, and peripheral ligaments that were similar to those of the human knee.

Influence of custom-made and stock mouthguard thickness on biomechanical response to a simulated impact

BACKGROUND/AIMS

Mouthguards (MGs) are devices that can reduce the risks of facial trauma. However, the large variety of MG types and thicknesses raises the question of which type is the most effective and beneficial for the athletes. The aim of this study was to evaluate stress distribution in the skull, teeth, and jaws as a consequence of a direct impact.

MATERIAL AND METHODS

Using modeling software, a human skull was modeled and a human jaw was created with all teeth inserted into the respective alveolus. The models were divided according to the MG type (custom-made or stock) and thickness (1, 2, and 4 mm). Two models without MG were evaluated with and without teeth contact. The geometries were exported to analysis software and the materials were considered ideal. Fixation occurred at the base of the foramen magnum. The load (500 N) was applied on the canine tooth with a ball. Maximum principal (MPa) and Von-Mises results were obtained.

RESULTS

Without any protection, the generated tensile stress was of greater magnitude causing more damage in the absence of teeth contact. The presence of a MG significantly reduced the generated stress in all structures, and the customized/individualized type was more efficient than stock MGs.

CONCLUSIONS

In extreme situations when it is impossible to use a MG, keeping the teeth in maximum intercuspal position is less harmful. Despite this, the use of any MG is beneficial and assists in dampening the generated stress. The thicker the device, the greater the capacity for decreasing the damage in all structures. The use of individual protectors for each patient is even more beneficial for preventing trauma during at-risk activities of impact.

Dental trauma prevention with mouthguard in a nose fracturing blow to the face: Case report

Orofacial injuries are common in sports activities and may vary in complexity and the tissues involved. Most sports-related trauma occurs when a player hits another player, an object or the ground. This report presents a case of an injury caused by a punchlike blow to the face during a handball college team practice session. The patient suffered a traumatic blow to the left side of the nose and mouth and promptly attended a dentist. After a clinical examination and a CBCT scan, the following injuries were diagnosed: upper lip laceration, upper left lateral incisor subluxation and anterior nasal spine fracture. More severe teeth injuries were likely prevented because the patient was wearing a mouthguard.