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Effect of Thermal Shrinkage of Extruded Sheet on Mouthguard Thickness: Influence of Model Undercut

Materials Sciences and Applications 2022年第1期13卷 54-62页

作者： Mutsumi takahashi Yogetsu Bando Department of Physiology The Nippon Dental University School of Life Dentistry at Niigata Niigata Japan BANDO Dental Clinic Ishikawa Japan

The effectiveness and safety of the mouthguard are greatly affected by its thickness. The aim of this study was to investigate the effect of thermal shrinkage of the extruded sheet on the mouthguard thickness depending on the amount of undercut of the model. Mouthguard sheet was used a 4.0 mm thick ethylene-vinyl acetate resin manufactured by extrusion molding. The sheets were placed in the vacuum forming machine with the sheet extrusion direction either vertical (condition V) or parallel (condition P) to the model’s centerline. The working models were three hard plaster models trimmed so that the angles of the anterior teeth to the model base were 90?, 100?, and 110? (Models A, B, and C). The sheet was softened until it sagged 15 mm, and then suction was continued for 30 s. Measurement points of the mouthguard were the incisal portion (incisal edge and labial surface) and molar portion (cusp and buccal surface). The differences in the reduction rate of the thickness due to model form and extrusion direction were analyzed using two-way ANOVA and Bonferroni’s multiple comparison tests. Differences in thickness depending on the extrusion direction of the sheet were observed in Models B and C on the labial surface and in all models on the buccal surface, and the thicknesses obtained under condition P were significantly thinner than those obtained under condition V. The thicknesses of the incisal edge and the cusp were not affected by the extrusion direction. The result of this study was suggested that the labial and buccal thickness of the mouthguard was secured by placing the sheet in the extrusion direction vertical to the model’s centerline. Furthermore, it was clarified that the presence of the undercut of the model tends to increase the influence of the extrusion direction of the sheet on the thickness of the mouthguard.

关键词： Mouthguard Extrusion Molding Thickness Model Angle Undercut

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Dependence of Thermoformed Mouthguard Thickness on Model Height in Single-Layer and Laminated Mouthguards

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Materials Sciences and Applications 2022年第8期13卷 469-478页

作者： Mutsumi takahashi Yogetsu Bando Department of Physiology The Nippon Dental University School of Life Dentistry at Niigata Niigata Japan BANDO Dental Clinic Ishikawa Japan

The height of the working model affects the mouthguard thickness. The aim of this study was to clarify the difference in the effect of model height on the thickness between single- and double-layered mouthguards. Mouthguards were thermoformed using ethylene-vinyl-acetate sheets and a pressure molding machine. Working models were three hard gypsum models with the height of the anterior part trimmed to 25 mm (model A), 30 mm (model B), and 35 mm (model C). Three molding conditions were compared: a single-layered mouthguard using a 4.0-mm thick-sheet (S4);a double-layered mouthguard using a 3.0-mm-thick sheet on the first-layer and a 2.0-mm-thick sheet on the second-layer (L32);and a double-layered mouthguard using 3.0-mm-thick sheets on first- and second-layers (L33). Analysis was performed by two-way ANOVA and a simple main effect test for the differences in the mouthguard thickness depending on the model height and the molding condition. Under all molding conditions, the labial and buccal thicknesses tended to become thinner as the model height increased, and models B and C were thinner by about 6% - 7% and about 14% - 16% than model A, respectively. The cusp thickness was not affected by the model height in L32 and L33, but in S4, models B and C were thinner about 14% or more than model A. Significant differences were observed among molding conditions, and S4 P < 0.01). This study suggested that the degree of the decrease in mouthguard thickness due to the increase the model height was similar for the single- and double-layered mouthguards on the labial and buccal sides, and increasing the model height by 5 mm and 10 mm decreased the thickness by about 6% - 7% and about 14% - 16%, respectively. At the cusp, only the single-layered mouthguard was affected by the model height.

关键词： Mouthguard Thermoforming Thickness Working Model

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Numerical analysis of interaction between solute atom and extended dislocation using force multipoles

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Journal of Central South University 2014年第8期21卷 3000-3006页

作者： Hiroaki Morita Akiyuki takahashi Department of Mechanical Engineering Faculty of Science and TechnologyTokyo University of Science

The interaction between a solute atom and an extended dislocation was investigated using a continuum approximation method with force multipoles.The dislocation core structure of extended dislocation was modeled with the Peierls-Nabarro model discretized with a number of infinitesimal Volterra dislocations.The interaction energy and force between a nickel solute atom and perfect and extended dislocation in copper were successfully calculated using the force multipoles.The results clearly show that the core structure of extended dislocation weakens the interaction with solute atoms.The interaction energy and force for extended dislocations are almost the half of those for perfect dislocations.

关键词：溶质原子数值分析多极相互作用能 Volterra 扩展位错错位近似方法

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Effect of Molding Technique That Move Model Position Just before Formation in Production of Laminated Mouthguard

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Materials Sciences and Applications 2023年第6期14卷 325-335页

作者： Mutsumi takahashi Yogetsu Bando Department of Physiology The Nippon Dental University School of Life Dentistry at Niigata Niigata Japan BANDO Dental Clinic Ishikawa Japan

Many molding techniques have been researched to ensure the thickness of custom mouthguards. The aim of this study was to clarify the effect on the thickness of a laminated mouthguard of a molding technique in which the model position is moved forward just before molding. Mouthguards were molded using a 3.0-mm-thick ethylene vinyl acetate mouthguard sheet and a pressure molding machine. The molding method was the normal molding method (condition C) and the molding technique (condition MP) in which the model position was moved 20 mm forward just before molding. Regarding the molding of the first layer (F) and the second layer (S), the following four molding methods based on the combination of conditions C and MP were compared;FC-SC, FC-SMP, FMP-SC, and FMP-SMP. Differences in mouthguard thickness due to molding conditions for the first and second layers were analyzed by two-way ANOVA and Bonferroni’s multiple comparison test. Significant differences were observed among all molding conditions on the labial surface, and the thicknesses were in the order FC-SC < FC-SMP < FMP-SC < FMP-SMP. FMP-SMP was 4.67 mm thick, which was 1.39 mm thicker than FC-SC. FC-SC was the thinnest at the cusp, and a significant difference was observed between other molding conditions. On the buccal side, significant differences were observed between all conditions except FC-SMP and FMP-SC, and the thicknesses were in the order FC-SC < FC-SMP, FMP-SC < FMP-SMP. The results of this study suggested that the labial and buccal sides of laminated mouthguards could be made 1.4 and 1.2 times thicker when a molding technique that moves the model position just before formation was used for the first and second layers. The reduction in thickness was suppressed by approximately 23.2% and approximately 10.7% on the labial and buccal sides, respectively, compared with the normal molding method.

关键词： Laminated Mouthguard Thermoforming Molding Technique Thickness

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Factors Affecting Thermal Shrinkage of Mouthguard Sheet during Thermoforming: Model Shape and Sheet Material Thickness

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Materials Sciences and Applications 2022年第4期13卷 133-143页

作者： Mutsumi takahashi Yogetsu Bando Department of Physiology The Nippon Dental University School of Life Dentistry at Niigata Niigata Japan BANDO Dental Clinic Ishikawa Japan

The effectiveness and safety of the mouthguard depend on the sheet material thickness. The thickness of the thermoformed mouthguard is affected by the model undercut and the thermal shrinkage that occurs when the extruded-molded sheet is reheated. The aim of this study was to clarify the influence of the undercut amount of the model and the thickness of the sheet material on the thermal shrinkage of the extruded sheet. The mouthguard sheet used ethylene-vinyl acetate resin with a thickness of 4.0 mm (4M) and 3.0 mm (3M) and was manufactured by extrusion molding. The working models were three hard gypsum models with the undercut amount on the labial side trimmed to 0? (U0), 10? (U10), and 20? (U20). Mouthguard thickness after vacuum formation was compared between the conditions formed so that the extrusion direction was vertical (condition V) or parallel (condition P) to the model midline. Differences in the reduction rate of the mouthguard thicknesses of the labial and buccal side depending on the sheet extrusion direction, model angle, and sheet material thickness were analyzed by three-way ANOVA and Bonferroni method. The reduction rate of the thickness in condition P was significantly greater than in condition V under all conditions except U0-4M on the labial side and U0-4M and U10-4M on the buccal side. In all models, the reduction rate of the thicknesses was significantly greater in 3M than in 4M in the same extrusion direction. In both 4M and 3M, the reduction rate of the thicknesses tended to increase as the amount of undercut increased in each extrusion direction. This study suggested that a model with a large amount of undercut on the labial side or a thin sheet had a significant effect on the thermal shrinkage of the mouthguard sheet during thermoforming, which leads to the thinning of the mouthguard.

关键词： Mouthguard Thermoforming Thermal Shrinkage Model Shape Thickness

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Effect of Various Factors for the Electrochemical Adsorption of Polydopamine on TiO₂ Film

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Journal of Materials Science and Chemical Engineering 2022年第3期10卷 15-29页

作者： Naomu takahashi Mikito Kitayama Department of Life Environment and Applied Chemistry Fukuoka Institute of Technology Fukuoka Japan

To fabricate polydopamine-sensitized solar cells with improved solar power conversion efficiency, the effects of pH, buffer, adsorption time and electrode potential for the electrochemical oxidation and polymerization of dopamine on TiO2 film were investigated. The optimum pH was around 7. It was found that the use of a buffer, especially 2-(N-morpholino)ethanesulfonic acid, significantly deteriorated the electrochemical adsorption of polydopamine, and the highest solar power conversion efficiency was obtained without buffer. With increasing adsorption time, the amount of adsorbed polydopamine increased but the solar power conversion efficiency decreased, suggesting the increased resistivity of polydopamine with a larger degree of polymerization. It was suggested that the reversal of electrode potential from positive to negative would be essential for the electrochemical adsorption of polydopamine.

关键词： Dye-Sensitized Solar Cell Dopamine Polydopamine Electrochemical Adsorption Buffer

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Zircon within chromitite requires revision of the tectonic history of the Eoarchean Itsaq Gneiss complex,Greenland

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Geoscience Frontiers 2023年第6期14卷 273-285页

作者： Hikaru Sawada Tomoaki Morishita Adrien Vezinet Richard Stern Kenichiro Tani Ikuya Nishio Kanta takahashi D.Graham Pearson Kristoffer Szilas Department of Earth System Science University of ToyamaToyamaJapan X-Star Japan Agency for Marine-Earth Science and Technology(JAMSTEC)KanagawaJapan Faculty of Geosciences and Civil Engineering Kanazawa UniversityKanazawaJapan Lamont-Doherty Earth Observatory Columbia UniversityPalisadesUSA Volcanoes and Earth’s Interior Research Center JAMSTECKanagawaJapan Department of Earth and Atmospheric Sciences University of AlbertaEdmontonCanada Canadian Centre for Isotopic Microanalysis University of AlbertaEdmontonCanada National Museum of Nature and Science TsukubaJapan Department of Geosciences and Natural Resource Management University of CopenhagenCopenhagenDenmark

The Ujaragssuit Nunat layered(UNL)unit in the Itsaq Gneiss Complex,west Greenland,has been consid-ered to contain one of the oldest chromitites on Earth based on~ca.4.1 Ga Hadean whole rock Pt-Os model ages and ca.3.81 Ga zircon U-Pb age of the surrounding orthogneiss.This study obtained zircon from the chromitite within this unit as well as granitoid sheets that intruded into the UNL unit.In-situ U-Pb-Hf-O isotope measurements were made on the zircons.Zircons from both the chromitite and the intrusive granitoids show concordant U-Pb ages of ca.2.97-2.95 Ga.In contrast,Hf and 0 isotopic anal-yses indicate that zircons in the chromitites have a different origin from those in the intrusive granitoids.Zircons from granitoids yielded Th/U ratios higher than 0.2,initial Hf isotope ratios of 0.2805-0.2807(i.e,initial:Hf value of-11 to-5),andδ^(18)O values of mostly 6.0‰-7.0‰,which are typical for felsic igneous rocks in Archean continental crust.The least altered zircons from a chromitite exhibited initial Hf isotope ratios of 0.28078-0.28084(i.e.,initial:Hf value of-1.1 to-0.4),close the chondritic value at ca.3.0 Ga and the depleted mantle at ca.3.2 Ga.These zircons also haveδ^(18)O values of 4.2‰6.1‰which correspond to typical mantle values.The other chromitite zircons yielded Th/U ratios lower than 0.1,and Hf and 0 isotopic compositions ranging between the least altered zircons and the intrusive granitoid zir-cons.These results indicate that the zircons in the chromitites crystallized before or during the 2.97-2.95 Ga granitoid intrusion and most of the zircons were altered by subsequent metasomatism.Furthermore,the present results suggest that zircons in the chromitites originally had depleted Hf iso-topic compositions at ca.3.2-3.0 Ga.This can be explained by two different models of the evolution of the UNL unit.One is that if the UNL unit was formed at>3.81 Ga as previously thought,with the zircons in the chromitites subsequently being precipitated by ca.3.2-2.95 Ga during metamorphism or metaso-matism.The other

关键词： Archean Itsaq gneiss complex Ultramafic rock Metasomatism

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Placenta Previa Accreta and Previous Cesarean Section：Some Clarifications

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Chinese Medical Journal 2018年第12期131卷 1504-1505页

作者： Shigeki Matsubara Hironori takahashi Department of Obstetrics and Gynecology Jichi Medical University Tochigi Japan

To the Editor： Placenta accreta （accreta, increta, or percreta） is challenging： effort to reduce its incidence is of paramount importance. We already know well that cesarean section （CS） increases the risk ofacc... 详细信息

关键词： DELIVERY

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Light chain cardiac amyloidosis in a nonagenarian

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Journal of Geriatric Cardiology 2022年第1期19卷 83-89页

作者： Koji takahashi Mina Yamashita Tomoki Sakaue Daijiro Enomoto Shigeki Uemura Takafumi Okura Shuntaro Ikeda Takanori Senba Akira Saijo Nobuhisa Yamamura Sohei Kitazawa Department of Community Emergency Medicine Ehime University Graduate School of MedicineEhimeJapan Department of Cardiology Yawatahama City General HospitalEhimeJapan Department of Hematology Yawatahama City General HospitalEhimeJapan Department of Clinical Pathology Yawatahama City General HospitalEhimeJapan Department of Molecular Pathology Ehime University Graduate School of MedicineEhimeJapan

Cardiac amyloidosis is an infiltrative and restrictive cardiomyopathy caused by the extracellular deposition of amyloid fib-rils within the heart as systemic amyloidosis,lead-ing to heart failure,reduced quality of life,and death.[1]There are two major amyloid fibril proteins that af-fect the heart:amyloid immunoglobulin light chain(AL)and amyloid transthyretin(ATTR).The latter is further subdivided into wild-type ATTR and variant types based on the presence of a mutation in the transthyretin gene.

关键词： amyloid death. cardiomyopathy

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Discrete dislocation plasticity analysis of dispersion strengthening in oxide dispersion strengthened(ODS) steels

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Journal of Central South University 2014年第4期21卷 1249-1255页

作者： Akiyuki takahashi Shota Sato Department of Mechanical Engineering Faculty of Science and TechnologyTokyo University of Science

A discrete dislocation plasticity analysis of dispersion strengthening in oxide dispersion strengthened(ODS) steels was described. Parametric dislocation dynamics(PDD) simulation of the interaction between an edge dislocation and randomly distributed spherical dispersoids(Y2O3) in bcc iron was performed for measuring the influence of the dispersoid distribution on the critical resolved shear stress(CRSS). The dispersoid distribution was made using a method mimicking the Ostwald growth mechanism. Then, an edge dislocation was introduced, and was moved under a constant shear stress condition. The CRSS was extracted from the result of dislocation velocity under constant shear stress using the mobility(linear) relationship between the shear stress and the dislocation velocity. The results suggest that the dispersoid distribution gives a significant influence to the CRSS, and the influence of dislocation dipole, which forms just before finishing up the Orowan looping mechanism, is substantial in determining the CRSS, especially for the interaction with small dispersoids. Therefore, the well-known Orowan equation for determining the CRSS cannot give an accurate estimation, because the influence of the dislocation dipole in the process of the Orowan looping mechanism is not accounted for in the equation.

关键词：弥散强化刃型位错塑性分析 ODS 氧化物离散剪切应力钢

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