Evaluation of thickness of 3D printed versus thermoformed aligners: A prospective in vivo ageing experiment.

BACKGROUND: To compare and investigate the effects of intraoral ageing on the thickness of one group of directly printed and two groups of thermoformed aligners on the labial surface of maxillary central incisors. MATERIALS AND METHODS: Six groups (12 samples per group) were included in this prospective in vivo experiment. Groups DP-Clin, INV-Clin and CA-Clin consisted of directly printed (Tera Harz TC-85 DAC resin), thermoformed (Invisalign, PU based polymer) and in house thermoformed (CA-Pro, PET-G based polymer) aligners, retrieved after 1 week of intraoral service. Groups DP-Ctr, INV-Ctr and CA-Ctr included unused aligners samples. Thickness measurements were conducted using confocal laser scanning microscopy (CLSM). Data that underwent log-10 transformation was analysed by multiple linear regression analysis (p < .05). RESULTS: Statistically significant differences were found between the materials in both Clin and Ctr categories (p < .001). Group DP had the highest thickness among the groups and the least thickness was observed in the CA group (p < .001). However, intraoral ageing did not significantly affect the aligner thickness of any groups. CONCLUSIONS: Both thermoforming and direct printing of clear aligners led to thickness deviations in terms of increase for printed aligners and decrease for thermoformed aligners. Intraoral ageing did not affect the aligner thickness in any of the groups.

Characterization of thin film Parylene C device curvature and the formation of helices via thermoforming.

In microfabricated biomedical devices, flexible, polymer substrates are becoming increasingly preferred over rigid, silicon substrates because of their ability to conform to biological tissue. Such devices, however, are fabricated in a planar configuration, which results in planar devices that do not closely match the shape of most tissues. Thermoforming, a process which can reshape thermoplastic polymers, can be used to transform flat, thin film, polymer devices with patterned metal features into complex three-dimensional (3D) geometries. This process extends the use of planar microfabrication to achieve 3D shapes which can more closely interface with the body. Common shapes include spheres, which can conform to the shape of the retina; cones, which can be used as a sheath to interface with an insertion stylet; and helices, which can be wrapped around nerves, blood vessels, muscle fibers, or be used as strain relief feature. This work characterizes the curvature of thin film Parylene C devices with patterned metal features built with varying Parylene thicknesses and processing conditions. Device curvature is caused by film stress in each Parylene and metal layer, which is characterized experimentally and by a mathematical model which estimates the effects of device geometry and processing on curvature. Using this characterization, an optimized process to thermoform thin film Parylene C devices with patterned metal features into 0.25 mm diameter helices while preventing cracking in the polymer and metal was developed.

Preparation and Performance Analysis of 3D Thermoformed Fluidic Polymer Temperature Sensors for Aquatic and Terrestrial Applications.

Employing a combination of Polyethylene terephthalate (PET) thermoforming and 3D-printed cylindrical patterns, we carefully engineer a linear resistive temperature sensor. This intricate process involves initial PET thermoforming, yielding a hollow cylindrical chamber. This chamber is then precisely infused with a composite fluid of graphite and water glue. Ensuring electrical connectivity, both ends are affixed with metal wires and securely sealed using a hot gun. This cost-effective, versatile sensor adeptly gauges temperature shifts by assessing composite fluid resistance alterations. Its PET outer surface grants immunity to water and solubility concerns, enabling application in aquatic and aerial settings without extra encapsulation. Rigorous testing reveals the sensor's linearity and stability within a 10 °C to 60 °C range, whether submerged or airborne. Beyond 65 °C, plastic deformation arises. To mitigate hysteresis, a 58 °C operational limit is recommended. Examining fluidic composite width and length effects, we ascertain a 12 Ω/°C sensitivity for these linear sensors, a hallmark of their precision. Impressive response and recovery times of 4 and 8 s, respectively, highlight their efficiency. These findings endorse thermoforming's potential for fabricating advanced temperature sensors. This cost-effective approach's adaptability underscores its viability for diverse applications.

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.

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

Maintenance Strategies for Industrial Multi-Stage Machines: The Study of a Thermoforming Machine.

The study of reliability, availability and control of industrial manufacturing machines is a constant challenge in the industrial environment. This paper compares the results offered by several maintenance strategies for multi-stage industrial manufacturing machines by analysing a real case of a multi-stage thermoforming machine. Specifically, two strategies based on preventive maintenance, Preventive Programming Maintenance (PPM) and Improve Preventive Programming Maintenance (IPPM) are compared with two new strategies based on predictive maintenance, namely Algorithm Life Optimisation Programming (ALOP) and Digital Behaviour Twin (DBT). The condition of machine components can be assessed with the latter two proposals (ALOP and DBT) using sensors and algorithms, thus providing a warning value for early decision-making before unexpected faults occur. The study shows that the ALOP and DBT models detect unexpected failures early enough, while the PPM and IPPM strategies warn of scheduled component replacement at the end of their life cycle. The ALOP and DBT strategies algorithms can also be valid for managing the maintenance of other multi-stage industrial manufacturing machines. The authors consider that the combination of preventive and predictive maintenance strategies may be an ideal approach because operating conditions affect the mechanical, electrical, electronic and pneumatic components of multi-stage industrial manufacturing machines differently.

Uncertainty Evaluation in Vision-Based Techniques for the Surface Analysis of Composite Material Components.

In this paper, a methodology is discussed concerning the measurement of yarn's angle of two different glass-reinforced polypropylene matrix materials, widely used in the production of automotive components. The measurement method is based on a vision system and image processing techniques for edge detection. Measurements of angles enable, if accurate, both useful suggestions for process optimization to be made, and the reliable validation of the simulation results of the thermoplastic process. Therefore, uncertainty evaluation of angle measurement is a mandatory pre-requisite. If the image acquisition and processing is considered, many aspects influence the whole accuracy of the method; the most important have been identified and their effects evaluated with reference to two different materials, which present different optical-type characteristics. The influence of piece geometry has also been taken into account, carrying out measurements on flat sheets and on a semi-spherical object, which is a reference standard shape, to verify the effect of thermoforming and to tune the process parameters. Complete uncertainty in the order of a few degrees has been obtained, which is satisfactory for purposes of simulation validation and consequent process optimization. The uncertainty budget also allowed individuation of the most relevant causes of uncertainty for measurement process improvement.

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.

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.

Thermoforming technique for suppressing reduction in mouthguard thickness: Part 2 Effect of model height and model moving distance.

BACKGROUND/AIM: Wearing a mouthguard reduces the risk of sports-related injuries, but the material and thickness of the mouthguard have a substantial impact on its effectiveness and safety. The aim of this study was to establish a thermoforming technique in which the model position is moved just before formation to suppress the reduction in thickness. The aim of this study was to assess the effects of model height and model moving distance on mouthguard thickness. MATERIALS AND METHODS: Ethylene-vinyl acetate sheets of 4.0 mm thick and a vacuum forming machine were used. Three hard plaster models were trimmed so that the height of the anterior teeth was 25 mm, 30 mm and 35 mm. Model position (MP) 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. The model was then pushed from behind to move it forward, and the vacuum was switched on. The model was moved at distances of 20 mm, 25 mm or 30 mm whereas a control model was not moved. Thickness after formation was measured with a specialized caliper. Differences in mouthguard thickness due to model height and moving distance were analysed by two-way ANOVA and Bonferroni's multiple comparison tests. RESULTS: Sheet thickness decreased as the model height increased. Each MP condition was significantly thicker than the control in each model. There was no significant difference among MP conditions except for the buccal surface. CONCLUSIONS: Moving the model forward by 20 mm or more just before formation is useful to secure the labial thickness of the mouthguard. This thermoforming technique increased the thickness by 1.5 times or more compared with the normal forming method, regardless of model height.

Thermoforming method to effectively maintain mouthguard thickness: Effect of moving the model position just before vacuum formation.

BACKGROUND/AIMS: Mouthguards can reduce the risk of sports-related injuries but the sheet material and thickness have a large effect on their efficacy and safety. The aim of this study was to investigate the effect of the thermoforming technique that moves the model position just before vacuum formation. MATERIALS AND METHODS: Ethylene vinyl acetate sheets of 4.0-mm thickness and a vacuum forming machine were used. The working model was placed with its anterior rim positioned 40 mm from the front of the forming table. Three forming conditions were compared: (a) The sheet was formed when it sagged 15 mm at the top of the post under normal conditions (control); (b) the sheet frame was lowered to and heated at 50 mm from the level of ordinary use, and the sheet was formed when it sagged 15 mm (LH); and (c) the sheet frame at the top of the post was lowered and covered on the model when it sagged 15 mm. Subsequently, the rear side of the model was pushed to move it forward 20 mm, and it was then formed (MP). Sheet thickness after fabrication was determined for the incisal edge, labial surface, and buccal surface using a specialized caliper accurate to 0.1 mm. Thickness differences among forming conditions were analyzed by one-way ANOVA and Bonferroni's multiple comparison tests. RESULTS: A significant difference was observed for all measurement points, and the thickness after formation increased in the order of control, LH, and MP. Particularly on the labial surface, MP was able to yield about 1.7 times the thickness (about 3.1 mm) of the control. CONCLUSION: The forming method of moving the model forward just before vacuum formation was effective for suppressing the mouthguard thickness reduction, which is capable of securing the labial thickness at 3 mm or more with a single layer.

Thermoforming technique for maintaining the thickness of single-layer mouthguard during pressure formation.

BACKGROUND/AIM: Using mouthguards can reduce the risk of injury when playing sports, but the sheet material and thickness have a large effect on their efficacy and safety. The aim of this study was to investigate the effect of moving the model position just before formation in the pressure forming technique to maintain the thickness of a single-layer mouthguard. MATERIALS AND METHODS: A 4.0-mm-thick ethylene vinyl acetate (EVA) mouthguard sheet (diameter: 125 mm) and a pressure forming machine were used. The working model was placed with its anterior rim positioned 40 mm from the front of the forming table. The sheets were placed in the forming table with the sheet extrusion direction either vertical (V) or parallel (P) to the model's centerline. Two molding methods were compared: (a) The sheet was formed when it sagged 15 mm (control) and (b) the sheet was covered on the model when it sagged 15 mm, next the model was pushed forward 20 mm, and the sheet was then formed (MP). Mouthguard thickness was measured for the labial surface, palatal surface, cusp, and buccal surface using a specialized caliper. Thickness differences according to molding methods and sheet extrusion directions were analyzed by two-way ANOVA. RESULTS: The thicknesses of the labial surface, cusp, and buccal surface were significantly larger in MP than in the control (P < 0.01). In particular, the thickness differences caused by the molding method were large on the labial and buccal surfaces: For the control, the thicknesses were 1.9 ± 0.03 and 2.1 ± 0.02 mm, whereas for MP, they were 3.2 ± 0.03 and 2.9 ± 0.03 mm, respectively. CONCLUSION: The molding method of moving the model forward just before formation was useful as a thermoforming technique for maintaining the thickness of single-layer mouthguards during pressure forming with 4.0-mm-thick EVA sheet. This method produced labial and buccal thicknesses of 3.2 ± 0.03 and 2.9 ± 0.03 mm.

Movement of model position just before vacuum forming to ensure mouthguard thickness: Part 2 Effect of model moving distance.

BACKGROUND/AIM: Wearing a mouthguard during sports reduces the risk of dental injury via absorbing impact forces, and the effectiveness and safety of the mouthguard are closely linked to the mouthguard material and thickness. The aim of this study was to clarify the suppression effect of the thickness reduction of the mouthguard when changing the moving distance of the model forward in a stepwise manner. MATERIALS AND METHODS: Ethylene-vinyl acetate sheets of 4.0 mm thick and a vacuum forming machine were used. The working model was placed at a position 40 mm from the front of the forming unit. The sheet was softened until it sagged 15 mm, and the sheet frame was lowered and covered the model. The model was then pushed from the back to move it forward, and the vacuum was switched on. The model was moved 10 (MP-10), 20 (MP-20), or 30 mm (MP-30). The control model was not moved. The thickness after formation was measured with a specialized caliper. Differences in the mouthguard thickness caused by the forming conditions were analyzed by one-way ANOVA and Bonferroni's multiple comparison tests. RESULTS: Significant differences were observed between the control and each MP condition (P < 0.01). Reduction rate of the thickness decreased as the moving distance of the model increased. In particular, the thickness difference depending on the forming conditions was greater at the labial site. The reduction rate of MP-30 was 33.8 ± 0.8% smaller than that of the control. CONCLUSION: The thickness reduction in mouthguards was mitigated by moving the model forward just before vacuum forming. The reduction was smaller as the moving distance of the model increased. This study suggested that moving the model 20 mm or more forward just before vacuum forming could secure the labial thickness of 3 mm or more.

Effect of the anteroposterior position of the model on fabricated mouthguard thickness: Part 2 Influence of sheet thickness and material.

AIM: Mouthguards can reduce the risk of sports-related injuries, but the sheet material and thickness have a large effect on their efficacy and safety. The aim of this study was to investigate the thickness of molded mouthguards when the model position on the forming table was changed stepwise in the anteroposterior direction for different sheet thicknesses and materials. MATERIALS AND METHODS: Ethylene vinyl acetate sheets and olefin copolymer sheets with 4.0 or 2.0 mm thick were used for thermoforming by a pressure-forming machine. The working model was trimmed to the height of 25 mm at the maxillary central incisor and 20 mm at first molar. The model was placed with its anterior rim positioned 40, 30, 25, 20, or 10 mm from the front of the sheet frame. Sheet thickness after fabrication was determined for the incisal edge, labial surface, and buccal surface using a specialized caliper. The differences of the model position on the thickness reduction were analyzed by two-way analysis of variance and Bonferroni's multiple comparison tests. RESULTS: Thickness reductions at the incisal edge, labial surface, and buccal surface were about -60%, -50%, and -40%, respectively; for a distance of 25 mm up to the height of the anterior part of the model and the frame from the model rim, the 4.0 and 2.0 mm sheets showed similar thickness reduction. When the model was moved forward, the anterior thickness reduction of the 2.0-mm-thick sheet increased to larger than that of the 4.0-mm-thick sheet. CONCLUSION: The thickness reduction of the mouthguard was not affected by the sheet material and thickness when the distance from the model to the frame was the same. However, when the distance between the model and the frame decreased, the thickness reduction of the adjacent portion of the model increased, such that the influence was larger in thin sheets.

Shape change in mouthguard sheets during thermoforming - part 2: effect of the anteroposterior position of the model on mouthguard thickness.

BACKGROUND/AIM: Mouthguards can reduce the risk of sports-related injuries, but the sheet material and thickness have a large effect on their efficacy and safety. The aim of this study was to investigate the effect of model position in the molding machine on the reduction in mouthguard thickness. MATERIALS AND METHODS: Ethylene vinyl acetate sheets and olefin copolymer sheets were used for thermoforming by a pressure- or a vacuum-forming machine. The working model was trimmed to the height of 25 mm at the maxillary central incisor and 20 mm at maxillary first molar. For both pressure forming and vacuum forming, the model was placed with the anterior rim of the model positioned 40, 30, 25, 20, or 10 mm from the front of the sheet frame. An additional test was carried out at 50 mm for vacuum forming. The sheet thickness after fabrication was determined for the incisal edge, labial surface, and buccal surface using a specialized caliper. The difference of the model position on the reduction in thickness in each forming device and sheet material was analyzed by one-way analysis of variance and Bonferroni's multiple comparison tests. RESULT: The reductions in thickness at the incisal edge and labial surface were about -60% and -50%, respectively, for the distance of 25 mm from the front of forming table. That position was the same as the height of the anterior part of the model for each molding machine and sheet material. The anterior thickness after molding became greater as the distance between the model and the sheet frame became smaller. CONCLUSION: The results showed that the thickness reduction was large when the distance from the model to the frame was small. This demonstrates the importance of centering the sheet and the model to achieve the most stable molding when positioning the model in the forming unit.

Effect of thermal shrinkage during thermoforming on the thickness of fabricated mouthguards: Part 2 pressure formation.

BACKGROUND: The aim of this study was to examine the effect of thermal shrinkage, which occurs during thermoforming of ethylene vinyl acetate (EVA) sheets on the thickness of mouthguards fabricated by pressure formation. MATERIALS AND METHODS: Mouthguards were fabricated from 4.0-mm-thick EVA sheets by utilizing a pressure-forming machine. Two molding conditions were compared: The sheets were placed in the thermoforming machine with the sheet extrusion direction either vertical or parallel to the model's center line. The working model was trimmed to the height of 20 mm at the cutting edge of the maxillary central incisor and 15 mm at the mesiobuccal cusp of the maxillary first molar. The sheet was pressed against the working model for 2 min where the center of the softened sheet sagged 15 mm lower than the clamp. After fabrication, the thickness of mouthguard sheets was determined for the incisal (incisal edge and labial surface) and molar (cusp and buccal surface) portions, and dimensional measurements were made. Differences in molded mouthguard thickness with the sheet orientation of extruded sheets were analyzed by Mann-Whitney U-test. RESULT: In comparison with the parallel axis orientation, the sheets in vertical orientation with the model's centerline yielded significantly higher thickness measurements at the incisal edge, labial surface, and the cusp (P < 0.01, respectively). CONCLUSION: The results suggest that the EVA sheet produced by extrusion molding in vertical axis orientation with the model's centerline can effectively reduce loss of thickness in mouthguards after pressure formation.

Influence of continuous use of a vacuum-forming machine for mouthguard thickness after thermoforming.

BACKGROUND/AIMS: Mouthguards can reduce the risk of sports-related injuries such as tooth fracture or avulsion, but the sheet material and thickness have a large effect on their efficacy and safety. The aim of this study was to investigate the effect of the continuous use of a vacuum-forming machine on mouthguard thickness. MATERIALS AND METHODS: Ethylene vinyl acetate sheets and olefin copolymer sheets were used for thermoforming with a vacuum-forming machine. The working model was trimmed to a height of 23 mm at the maxillary central incisor and 20 mm at maxillary first molar. During molding, the model was placed at the center of the vacuum unit. Three molding conditions were investigated (i) molding was carried out after the sag at the center of the softened sheet was 15 mm below the clamp (control); (ii) sheet heating started 5 minutes after the control, and molding in the same way as the control (AF5); and (iii) sheet heating started 10 minutes after the control, and molding in the same way as the control (AF10). Under each condition, vacuum forming was conducted for 30 seconds. Sheet thickness after fabrication was determined for the incisal edge, labial surface, cusp, and buccal surface using a special caliper accurate to 0.1 mm. The differences of the molding conditions on the thickness in each sheet material were analyzed by one-way analysis of variance and Bonferroni's multiple comparison tests. RESULTS: For both sheet materials, significant differences between the control and AF5 were observed at all measurement points (P<.01), but not between the control and AF10. Compared with the control, AF5 was thinner and AF10 was a similar thickness. CONCLUSION: The continuous use of a vacuum-forming machine led to a reduction in the thickness of the mouthguard. Intervals of 10 minutes are necessary to achieve consistent molding.

The effect of model inclination during fabrication on mouthguard calliper-measured and CT scan-assessed thickness.

AIM: Excessive material thinning has been observed in the production of custom-made mouthguards in a number of studies, due to production anomalies that may lead to such thinning. This study investigated thinning material patterns of custom-made mouthguards when the anterior angulation of dental model was increased during the thermoforming process. MATERIALS AND METHODS: A total of 60 samples of mouthguard blanks were thermoformed on identical maxillary models under four anterior inclination conditions (n = 4 × 15): control 0, 15, 30 and 45°. Each mouthguard sample was measured, using an electronic calliper gauge at three anatomical points (anterior labial sulcus, posterior occlusion and posterior lingual). Mouthguards were then CT scanned to give a visual representation of the surface thickness. RESULTS: Data showed a significant difference (P < 0.005) in the anterior mouthguard thickness between the four levels of anterior inclination, with the 45° inclination producing the thickest mouthguards, increasing the mean anterior thickness by 75% (2.8 mm, SD: 0.16) from the model on a flat plane (1.6 mm, SD: 0.34). Anterior model inclination of 30 and 45° inclinations increased consistencies between the thickest and thinnest mouthguards in the anterior region of these sample groups. CONCLUSION: This study highlights the importance of standardizing the thermoforming process, as this has a significant effect on the quality and material distribution of the resultant product. In particular, greater model inclination is advised as this optimizes the thickness of the anterior sulcus of the mouthguard which may be more prominently at risk from sport-related impact.

Shape change in mouthguard sheets during thermoforming.

BACKGROUND: The purpose of this study was to identify changes in sheet shape during thermoforming and the effect of the model position in the molding machine on fabricated mouthguard thickness. MATERIALS AND METHODS: Ethylene vinyl acetate mouthguard sheets (3.8 mm thick) were used that had cross-stripes (10 × 10 mm), and the anteroposterior and bilateral lengths were used for measurements. Two forming machines were used: a vacuum- and a pressure-forming machine, and two heating conditions were investigated that defined as the time when sagging of the softened sheet was 15 mm (H-15) and 20 mm (H-20) below the clamp, and the length of each cross-stripes was measured. The area of each lattice was calculated using Bretschneider's formula to compare changes in sheet shape for each condition. Next, mouthguards were molded by forming machine where the working model was positioned under two different conditions: with the model anterior centered in the forming unit and with the model centered. The sheet thickness after fabrication was determined for the incisal and the molar portion, and dimensional measurements were obtained using a measuring device. Differences in the thickness were analyzed by two-way analysis of variance (anova). RESULT: In both molding machines, the change in the area under H-20 was greater than H-15. While the increase in area tended to expand from the center of the sheet in concentric circles, the difference between the central and surrounding areas was only approximately 5%. For both molding machines, differences in thickness after molding due to setting position of the model were not observed. CONCLUSION: The results showed that shape changes of the sheet during thermoforming tend to concentrically and almost uniformly expand from the center and that it is important to center the sheet and the model when positioning the model in the forming unit.

An investigation into the relationship between thickness variations and manufacturing techniques of mouthguards.

BACKGROUND: The aim of this study was to measure the finished thickness of a single identical 4-mm EVA mouthguard model from a large fabricated sample group and to evaluate the degree of material thinning and variations during the fabrication process. MATERIALS AND METHODS: Twenty boxes were distributed to dental technician participants, each containing five duplicated dental models (n = 100), alongside 5 × 4 mm mouthguard blanks and a questionnaire. The mouthguards were measured using electronic callipers (resolution: ±0.01 mm) at three specific points. The five thickest and thinnest mouthguards were examined using a CT scanner to describe the surface typography unique to each mouthguard, highlighting dimensional thinning patterns during the fabrication process. RESULTS: Of the three measurement points, the anterior sulcus point of the mouthguard showed a significant degree of variation (up to 34% coefficient of variation), in finished mouthguard thickness between individuals. The mean thickness of the mouthguards in the anterior region was 1.62 ± 0.38 mm with a range of 0.77-2.80 mm. This variation was also evident in the occlusion and posterior lingual regions but to a lesser extent (up to 12.2% and 9.8% variations, respectively). CONCLUSION: This study highlights variability in the finished thickness of the mouthguards especially in the anterior sulcus region measurement point, both within and between individuals. At the anterior region measurement point of the mouthguard, the mean thickness was 1.62 mm, equating to an overall material thinning of 59.5% when using a single 4-mm EVA blank. This degree of thinning is comparative to previous single operator research studies.