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The manufacturing processes and design of metal and alloy products can be performed over a wide range of strain rates and temperatures. To design and optimize these processes using computational mechanics tools, the selection and calibration of the constitutive models is critical. In the case of hazardous and explosive impact loads, it is not always possible to test material properties. For this purpose, this paper assesses the efficiency and the accuracy of different architectures of ANNs for the identification of the Johnson-Cook material model parameters. The implemented computational tool of an ANN-based parameter identification strategy provides adequate results in a range of strain rates required for general manufacturing and product design applications. Four ANN architectures are studied to find the most suitable configuration for a reduced amount of experimental data, particularly for cases where high-impact testing is constrained. The different ANN structures are evaluated based on the model's predictive capability, revealing that the perceptron-based network of 66 inputs and one hidden layer of 30 neurons provides the highest prediction accuracy of the effective flow stress-strain behavior of Ti64 alloy and three virtual materials.

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This study evaluates a binary mixture of fly ash and lime as a stabilizer for natural soils. A comparative analysis was performed on the effect on the bearing capacity of silty, sandy and clayey soils after the addition of lime and ordinary Portland cement as conventional stabilizers, and a non-conventional product of a binary mixture of fly ash and Ca(OH)2 called FLM. Laboratory tests were carried out to evaluate the effect of additions on the bearing capacity of stabilized soils by unconfined compressive strength (UCS). In addition, a mineralogical analysis to validate the presence of cementitious phases due to chemical reactions with FLM was performed. The highest UCS values were found in the soils that required the highest water demand for compaction. Thus, the silty soil added with FLM reached 10 MPa after 28 days of curing, which was in agreement with the analysis of the FLM pastes, where soil moistures higher than 20% showed the best mechanical characteristics. Furthermore, a 120 m long track was built with stabilized soil to evaluate its structural behavior for 10 months. An increase of 200% in the resilient modulus of the FLM-stabilized soils was identified, and a decrease of up to 50% in the roughness index of the FLM, lime (L) and Ordinary Portland Cement (OPC)-stabilized soils compared to the soil without addition, resulting in more functional surfaces.

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Four imidazolium-based ionic liquids (IL; 1-butyl-3-methylimidazolium chloride, 1-carboxymethyl-3-methylimidazolium chloride, 1,3-dicarboxymethylimidazolium chloride and 1-(2-hydroxyethyl) -3-methylimidazolium chloride) were tested as compatibilizers of microcrystalline cellulose (MCC). Subsequently, ethanolic IL solutions were prepared; MCC was mixed, and the mixtures were left to evaporate the ethanol at ambient conditions. These modified MCC were characterized and applied as reinforcements (5.0 and 10 phr) in an epoxy resin aiming to manufacture biobased composites with enhanced performances. The IL did not significantly modify the morphological and structural characteristics of such reinforcements. Regarding the thermal stability, the slight increase was associated with the MCC-IL affinity. The IL-modified MCC-epoxy composites presented improved mechanical responses, such as flexural strength (≈22.5%) and toughness behavior (≈18.6%), compared with pure epoxy. Such improvement was also obtained for the viscoelastic response, where the storage modulus at the glassy state depended on the MCC amount and IL type. These differences were associated with stronger hydrogen bonding between IL and epoxy hardener or the IL with MCC, causing a "bridging" effect between MCC and epoxy matrix.

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Agricultural systems are facing the negative impacts of erosion and water scarcity, directly impacting the hydro-mechanical behavior of soil aggregation. Several technologies have been proposed to reduce hydro-mechanical soil-related problems in agriculture. Biopolymer-based hydrogels have been reported to be a great tool to tackle these problems in soils. In this study, we investigated the hydro-mechanical behavior of different soils media treated with Ca-bacterial alginate hydrogel. We used an unconfined uniaxial compression test, aggregate stability test and hydraulic conductivity measurements to investigate the mechanical and hydraulic behavior of treated soils media. Our results from unconfined uniaxial compression test showed that yield stress (i.e., strength) increased in treated soils with higher kaolinite and water content (i.e., HCM3), compared with untreated coarse quartz sand (i.e., CM1). Furthermore, we found that temperature is an important factor in the gelation capacity of our hydrogel. At room temperature, HCM3 displayed the higher aggregate stability, almost 5.5-fold compared with treated coarse quartz sand (HCM1), while this differential response was not sustained at warm temperature. In general, the addition of different quantities of kaolinite decreased the saturated hydraulic conductivity for all treatments. Finally, bright field microscopy imaging represents the soil media matrix between sand and clay particles with Ca-bacterial alginate hydrogel that modify the hydro-mechanical behavior of different soils media. The results of this study could be helpful for the soil-related problems in agriculture facing the negative effects of climate change.

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Chitosan-gold nanoparticle (CS/AuNP) thin films were synthesized through the chemical reduction of HAuCl4 in sodium citrate/chitosan solutions. The dielectric and dynamic mechanical behaviors of CS/AuNP films have been investigated as a function of moisture and HAuCl4 content. Two relaxation processes in the nanocomposites have been observed. The α-relaxation process is related to a glass transition in wet CS/AuNP films. However, in dry composites (with 0.2 wt% of moisture content), the glass transition vanished. A second relaxation process was observed from 70 °C to the onset of thermal degradation (160 °C) in wet films and from 33 °C to the onset of degradation in dry films. This relaxation is identified as the σ-relaxation and may be related to the local diffusion process of ions between high potential barriers in disordered systems. The α- and σ-relaxation processes are affected by the HAuCl4 content of the solutions from which films were obtained because of the interaction between CS, sodium succinate, and gold nanoparticles. With about 0.6 mM of HAuCl4, the conductivity of both wet and dry films sharply increased by six orders, corresponding to the percolation effect, which may be related to the appearance of a conductivity pathway between AuNPs, HAuCl4, and NaCl.

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In a recent paper, novel polyester nanocomposites reinforced with up to 3 wt% of cellulose nanocrystals (CNCs) extracted from conifer fiber were characterized for their crystallinity index, water absorption, and flexural and thermal resistance. The use of this novel class of nanocomposites as a possible substitute for conventional glass fiber composites (fiberglass) was then suggested, especially for the 1 and 2 wt% CNC composites due to promising bending, density, and water absorption results. However, for effective engineering applications requiring impact and tensile performance, the corresponding properties need to be evaluated. Therefore, this extension of the previous work presents additional results on Izod and tensile tests of 1 and 2 wt% CNC-reinforced polyester composites, together with a comparative cost analysis with fiberglass. The chemical effect caused by incorporation of CNCs into polyester was also investigated by FTIR. In comparison to the neat polyester, the Izod impact energy increased 50% and 16% for the 1 and 2 wt% composites, respectively. On the other hand, the tensile strength and Young's modulus remained constant within the ANOVA statistical analysis. FTIR analysis failed to reveal any chemical modification caused by up to 2 wt% CNC incorporation. The present impact and tensile results corroborate the promising substitution of a polyester composite reinforced with very low amount of CNCs for common fiberglass in engineering application.

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Commercially pure (c.p.) titanium grade IV with a bimodal microstructure is a promising material for biomedical implants. The influence of the processing parameters on the physical, microstructural, and mechanical properties was investigated. The bimodal microstructure was achieved from the blends of powder particles with different sizes, while the porous structure was obtained using the space-holder technique (50 vol.% of ammonium bicarbonate). Mechanically milled powders (10 and 20 h) were mixed in 50 wt.% or 75 wt.% with c.p. titanium. Four different mixtures of powders were precompacted via uniaxial cold pressing at 400 MPa. Then, the specimens were sintered at 750 °C via hot pressing in an argon gas atmosphere. The presence of a bimodal microstructure, comprised of small-grain regions separated by coarse-grain ones, was confirmed by optical and scanning electron microscopies. The samples with a bimodal microstructure exhibited an increase in the porosity compared with the commercially available pure Ti. In addition, the hardness was increased while the Young's modulus was decreased in the specimens with 75 wt.% of the milled powders (20 h).

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Dental interfaces are subject to mixed-mode loading. This study provides practical guidance for determining interfacial fracture toughness of dental ceramic systems. We address interfacial fracture of a composite resin cement sandwiched between two dental ceramic materials. Emphasis is placed on sandwich disc specimens with cracks originating from elliptical-shaped flaws near the center, for which analytical fracture mechanics methods fail to predict. The interaction integral method is used to provide accurate finite element solutions for cracks with elliptical-shaped flaws in a Brazil-nut-sandwich specimen. The developed model was first validated with existing experimental data and then used to evaluate the three most widely used dental ceramic systems: polycrystalline ceramics (zirconia), glass-ceramics (lithium disilicate), and feldspathic ceramics (porcelain). Contrary to disc specimens with ideal cracks, those with cracks emanating from elliptical-shaped flaws do not exhibit a monotonic increase in interfacial toughness. Also, interfacial fracture toughness is seen to have a direct relationship with the aspect ratio of elliptical-shaped flaws and an inverse relationship with the modulus ratio of the constituents. The presence of an elliptical-shaped flaw significantly changes the interfacial fracture behavior of sandwich structures. Semi-empirical design equations are provided for fracture toughness and stress intensity factors for interfacial cracks. The developed design equations provide practical guidance for determining interfacial fracture toughness of selected dental ceramic material systems. Those equations take into account four critical factors: size of the elliptical flaw, modulus ratio of constituent materials, loading angle, and applied load.

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The application of cellulose nanocrystal has lately been investigated as polymer composites reinforcement owing to favorable characteristics of biodegradability and cost effectiveness as well as superior mechanical properties. In the present work novel nanocomposites of unsaturated polyester matrix reinforced with low amount of 1, 2, and 3 wt% of cellulose nanocrystals obtained from conifer fiber (CNC) were characterized. The polyester matrix and nanocomposites were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), bending test, and thermogravimetric analysis (TGA). The result showed that the addition of only 2 wt% CNC increased the nanocomposite flexural strength by 159%, the ductility by 500% and the toughness by 1420%. Fracture analyses by SEM revealed a uniform participation of the CNC in the polyester microstructure. The resistance to thermal degradation of the CNC reinforced nanocomposites was improved in more than 20 °C as compared to neat polyester. No significant changes were detected in the water absorptions and XRD pattern of the neat polyester with incorporations up to 3 wt% CNC. These results reveal that the 2 wt% CNC nanocomposite might be a promising more ductile, lightweight and cost-effective substitute for conventional glass fiber composites in engineering applications.

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In this work a Metal-Organic Framework (MOF) was prepared using a solvothermal method, taking as precursors 1. 2-di-(4-pyridyl)-ethylene, 1.2.4.5-benzenetetracarboxylic acid and Co(No3)2-6H2O. This MOF was called UV-11 and was evaluated using microscopic, spectroscopic and electrochemical techniques. According to the obtained results, the melting point of the compound is located in a higher interval than its precursors. Stereoscopic microscopy analysis shows the presence of pink crystals in the form of needles. MEB technique displays a laminar morphology as well as crystals with approximate sizes (36 mm wide and 150 mm long). EDS analysis corroborated the presence of precursor elements such as cobalt, carbon and oxygen. Furthermore, the XRD technique shows the cobalt-related phases in the sample, which is cobalt bis (pyridine-6-carboxylic-2-carboxylate). A modified carbon paste electrode was prepared using MOF UV-11 and by cyclic voltammetry electrochemical technique, semi-reversible redox processes are identified, as well as thermodynamic and kinetic parameters were obtained with the Laviron equation, and electrochemical performance properties from the cyclic voltammetry experimental data.

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A novel class of graphene-based materials incorporated into natural lignocellulosic fiber (NLF) polymer composites is surging since 2011. The present overview is the first attempt to compile achievements regarding this novel class of composites both in terms of technical and scientific researches as well as development of innovative products. A brief description of the graphene nature and its recent isolation from graphite is initially presented together with the processing of its main derivatives. In particular, graphene-based materials, such as nanographene (NG), exfoliated graphene/graphite nanoplatelet (GNP), graphene oxide (GO) and reduced graphene oxide (rGO), as well as other carbon-based nanomaterials, such as carbon nanotube (CNT), are effectively being incorporated into NLF composites. Their disclosed superior mechanical, thermal, electrical, and ballistic properties are discussed in specific publications. Interfacial shear strength of 575 MPa and tensile strength of 379 MPa were attained in 1 wt % GO-jute fiber and 0.75 wt % jute fiber, respectively, epoxy composites. Moreover, a Young's modulus of 44.4 GPa was reported for 0.75 wt % GO-jute fiber composite. An important point of interest concerning this incorporation is the fact that the amphiphilic character of graphene allows a better way to enhance the interfacial adhesion between hydrophilic NLF and hydrophobic polymer matrix. As indicated in this overview, two basic incorporation strategies have so far been adopted. In the first, NG, GNP, GO, rGO and CNT are used as hybrid filler together with NLF to reinforce polymer composites. The second one starts with GO or rGO as a coating to functionalize molecular bonding with NLF, which is then added into a polymeric matrix. Both strategies are contributing to develop innovative products for energy storage, drug release, biosensor, functional electronic clothes, medical implants, and armor for ballistic protection. As such, this first overview intends to provide a critical assessment of a surging class of composite materials and unveil successful development associated with graphene incorporated NLF polymer composites.

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Natural lignocellulosic fibers and corresponding fabrics have been gaining notoriety in recent decades as reinforcement options for polymer matrices associated with industrially applied composites. These natural fibers and fabrics exhibit competitive properties when compared with some synthetics such as glass fiber. In particular, the use of fabrics made from natural fibers might be considered a more efficient alternative, since they provide multidirectional reinforcement and allow the introduction of a larger volume fraction of fibers in the composite. In this context, it is important to understand the mechanical performance of natural fabric composites as a basic condition to ensure efficient engineering applications. Therefore, it is also important to recognize that ramie fiber exhibiting superior strength can be woven into fabric, but is the least investigated as reinforcement in strong, tough polymers to obtain tougher polymeric composites. Accordingly, this paper presents the preparation of epoxy composite containing 30 vol.% Boehmeria nivea fabric by vacuum-assisted resin infusion molding technique and mechanical behavior characterization of the prepared composite. Obtained results are explained based on the fractography studies of tested samples.

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Los fabricantes de Productos Médicos Implantables deben comprobar que sus productos son seguros y eficaces, entre otros requisitos pre-comercialización, para lograr su inscripción en el Registro Nacional de Productores y Productos de Tecnología Médica (R.P.P.T.M.). Una estrategia para demostrarlo es evaluar, entre otros atributos, su desempeño mecánico y compararlo con el de otros productos cuyo uso sea equivalente y ya se encuentren aprobados para su uso clínico. Información valiosa podría obtenerse si se contara con una base de datos que refleje el comportamiento mecánico de esta familia de productos a nivel nacional. El objetivo de este trabajo fue describir el comportamiento mecánico de placas y clavos de osteosíntesis de fabricación nacional a partir de ensayos realizados entre 2010 a 2019 en Instituto Nacional de Tecnología Industrial, INTI. En total se relevó información de ensayos de 29 modelos distintos de placas de osteosíntesis de 20 fabricantes nacionales y de 25 modelos distintos de clavos endomedulares de 16 fabricantes nacionales. Las placas se clasificaron según su uso previsto (1/3 de tubo, DCP o LC-DCP), su espesor y el material. Los clavos se clasificaron según la forma de la sección (canulada, maciza o ranurada), el diámetro y el material. Para la caracterización del comportamiento mecánico se analizaron ensayos de flexión en 4 puntos según las metodologías propuestas en las normas IRAM 9426/ISO 9585 y ASTM F382 para placas y la ASTM F1264 para clavos. Se calcularon la Rigidez a la flexión equivalente y la Resistencia a la flexión de acuerdo con lo propuesto en dichas normas. La información generada compila el desempeño mecánico de la industria nacional y sirve de referencia para los fabricantes y organismos de regulación para la evaluación de nuevos productos. Utilizando como variable de comparación el espesor/diámetro del implante se puede estimar los valores de Rigidez a la flexión equivalente y Resistencia a la flexión que deberían obtenerse al realizar los ensayos de flexión.

The manufacturers of Implantable Medical Devices must prove that their products are safe and effective, among other pre-market requirements, to achieve their registration in the National Registry of Producers and Products of Medical Technology (R.P.P.T.M.). A strategy to demonstrate its efficacy is to evaluate, among other design attributes, the mechanical behavior of the product to be commercialized and compare it with other products whose use is equivalent and are already approved for clinical use. Valuable information could be obtained by having a nationwide database that reflects the mechanical behavior of this family of products. The objective of this work was to describe the mechanical behavior of nationally manufactured osteosynthesis plates and nails based on the results obtained from tests carried out between 2010 and 2019 at the National Institute of Industrial Technology, INTI. In total, the information collected from tests consisted of 29 different models of osteosynthesis plates from 20 national manufacturers and 25 different models of intramedullary nails from 16 national manufacturers. The plates were classified according to their intended use (1/3 of tube, DCP or LC-DCP), thickness, and material. The nails were classified according to the cross section (cannulated, solid or grooved), the diameter, and material. In order to characterize the mechanical behavior, 4-point bending tests were carried out according to the test methods proposed in standards IRAM 9426/ISO 9585 and ASTM F382 for plates, and ASTM F1264 for nails. The equivalent bending stiffness and yield moment were calculated based on the methods proposed in these standards. The information generated compiles the mechanical behavior of the national industry and serves as a reference to manufacturers and regulatory agencies for the evaluation of new products. Using the thickness/diameter of the implant as a variable to be compared to, it is possible to estimate the equivalent bending stiffness and yield moment that should be obtained when performing the 4-point bending tests.

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OBJECTIVE: To evaluate the composition, flexural strength and fatigue behaviour of lithium disilicate ceramic (LD) after repeated firings and different staining techniques. METHODS: LD discs were fabricated and divided according to number of firing cycles and staining technique: CO - control, discs were crystallized (850°C/10min); SC - single-step characterization - crystallization and staining (applied with a thin brush) were performed in a single step with one firing cycle (850°C/10min); and DC - double-step characterization - crystallization firing cycle was performed first (850°C/10min), followed by staining firing cycle (770°C/90s). Specimens were fired two, four or six times (one crystallization firing cycle and one, three or five staining firing cycles), resulting into 9 groups (n=30): COII, COIV, COVI, SCII, SCIV, SCVI, DCII, DCIV and DCVI. The composition of the specimens was investigated (EDS, XRD, Raman spectroscopy), and the biaxial flexural strength (n=10) and staircase tests (n=20, 5×104 cycles, 5Hz) were performed. Data were subjected to one-way ANOVA and Tukey's test (α=0.05). RESULTS: EDS and XRD revealed amorphous content for stained groups. Biaxial flexural strength was not affected by repeated firings in any group, but stained groups presented lower flexural strength than control groups (p=0.001). The fatigue limit results decreased in all groups compared to flexural strength. SC groups showed similar (SCII and SCIV) or even higher fatigue limits (SCVI) than the control groups, and DC showed the lowest fatigue limit values. SEM and Raman suggested that the interfaces between staining and the LD showed only an overlap for the DC groups, whereas for the SC it was suggested an interaction between the stain and the LD. SIGNIFICANCE: Repeated firings did not result in decreased lithium disilicate flexural strength.Staining affected flexural strength and also resulted in increased amorphous content in the characterized specimens. Single-step staining resulted in the highest fatigue limit.

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This work reports the main conclusions of a study on the mechanical behavior of concrete under ISO 834 fire with different cooling methods. The aim of this research was to provide reliable data for the analysis of structures damaged by fire. The experimental program used cylindrical concrete test specimens subjected to ISO 834 heating in a furnace up to maximum gas temperatures of 400, 500, 600, 700, and 800 °C. The compressive strength was measured in three situations: (a) at the different temperature levels reached in the furnace; (b) after a natural cooling process; and (c) after aspersion with water at ambient temperature. The results indicate that the concrete residual compressive strength is fairly dependent on the maximum temperature reached in the furnace and revealed that concrete of a lower strength preserved relatively higher levels of strength. The cooling method significantly influenced the strength, albeit at a lower intensity. In all cases, the residual strength remained in the range of 38% to 67% of the strength at ambient temperature. The statistical analysis showed that the data obtained by the experimental program are significant and confirmed the influence of the conditions imposed on the residual strength.

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OBJECTIVE: To investigate the effect of intaglio surface adjustment of simplified lithium disilicate ceramic restorations adhesively cemented to a dentin-like material on its fatigue behavior. METHODS: Ceramic discs (IPS e.max CAD) were prepared and an in-Lab simulation of machining roughness was performed by grinding with SiC paper (#60). Ceramic discs were divided into 4 groups according to the internal adjustment of the cementation surface: no adjustments (CTRL); adjustment with a medium (M), fine (F), or extra fine (FF) diamond bur. Dentin-like material discs were also produced. Ceramic disc intaglio surfaces were etched (5% hydrofluoric acid; 20s) and received a silane coating. Dentin-like material discs were etched (10% hydrofluoric acid; 1min) and received a primer coating. Pairs of ceramic/dentin-like material were adhesively cemented (Multilink Automix), and fatigue failure load tests were performed using the Staircase approach (250,000 cycles; 20Hz). Roughness, topographic and fractographic analyses were performed. Statistical analyses were carried out through ANOVA tests. RESULTS: All ground groups (M=521.3 N; F=536.9 N; FF=676.2 N) presented lower fatigue failure load values than the control (1241.6 N). M diamond bur created a rougher surface than F (Ra and Rz parameters). However, FF was similar to F and M for Ra, and similar to F for Rz. SIGNIFICANCE: Bur adjustments on the intaglio surface of simplified lithium disilicate ceramic restorations greatly decreased the fatigue failure load even using an extra-fine diamond bur. Care should be taken when internal adjustments are needed.

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A relatively unknown natural fiber extracted from the leaves of the fique plant, native of the South American Andes, has recently shown potential as reinforcement of polymer composites for engineering applications. Preliminary investigations indicated a promising substitute for synthetic fibers, competing with other well-known natural fibers. The fabric made from fique fibers have not yet been investigated as possible composite reinforcement. Therefore, in the present work a more thorough characterization of fique fabric as a reinforcement of composites with a polyester matrix was performed. Thermal mechanical properties of fique fabric composites were determined by dynamic mechanical analysis (DMA). The ballistic performance of plain woven fique fabric-reinforced polyester matrix composites was investigated as a second layer in a multilayered armor system (MAS). The results revealed a sensible improvement in thermal dynamic mechanical behavior. Both viscoelastic stiffness and glass transition temperature were increased with the amount of incorporated fique fabric. In terms of ballistic results, the fique fabric composites present a performance similar to that of the much stronger KevlarTM as an MAS second layer with the same thickness. A cost analysis indicated that armor vests with fique fabric composites as an MAS second layer would be 13 times less expensive than a similar creation made with Kevlar™.

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OBJECTIVE: The purpose of this study was evaluate, for the first time, the impact of incorporation of nanostructured silver vanadate (ß-AgVO3) in antibiofilm and mechanical properties of dental acrylic resins (poly(methyl methacrylate), PMMA). DESIGN: The ß-AgVO3 was synthesized and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and microanalysis (SEM/EDS). Resins specimens were prepared with 0-10% wt.% ß-AgVO3 and characterized by SEM, XRD and optical microscopy. The antibiofim activity of the samples against Candida albicans and Streptococcus mutans was investigated by XTT reduction test, colony-forming units (CFUs), and confocal laser scanning microscopy (CLSM). The flexural strength, hardness, and surface roughness of the samples containing ß-AgVO3 were compared with the pure PMMA matrix. RESULTS: The incorporation of 10% ß-AgVO3 significantly reduced the metabolic activity of C. albicans and S. mutans (p<0.05). There was a reduction in microbial load (CFU/mL) of microorganisms for the different concentrations used (p<0.05), which was confirmed by confocal microscopy. The addition of ß-AgVO3 did not change the mechanical properties of hardness and surface roughness of the resins (p>0.05). However, flexural strength decreased with the addition of amounts greater than 1% (p<0.05). CONCLUSIONS: ß-AgVO3 additions in dental acrylic resin may have an impact on inhibition of biofilm of main microorganisms associated with dental prostheses. However, the viability of clinical use should be evaluated in function of changed promoted in some mechanical properties.

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Este estudio pretendió determinar el comportamiento mecánico entre pilares de Zirconio Zimmer® con anillo de Titanio en la base y sin ella, utilizando el método de análisis de elementos finitos Métodos: se diseñaron dos modelos de pilar en Zirconio sobre implante, conformados además por un implante de Titanio Zimmer® tornillo de unión, hueso cortical y hueso esponjoso y una corona cerámica de un incisivo central superior. Se aplicó fuerza en sentido oblicuo con una magnitud de 200N, ascendiendo en escala de 200N hasta que algún elemento superara el límite de proporcionalidad. Se calcularon los esfuerzos von Mises para cada elemento. Resultados: No se observaron diferencias en la magnitud de los esfuerzos de von Mises entre el pilar con anillo de Titanio y sin él; (280,1 MPa con anillo en Titanio, 280,4 MPa sin él) pero sí en el tornillo y el implante, siendo menores los esfuerzos para el modelo con anillo de Titanio (474 MPa 15 vs 576,7 MPa). El hueso y la corona reportaron no linealidad a 600N, implante y tornillo a 1000N y ambos pilares de Zirconio a 1400N. Conclusiones: Cuando el esfuerzo de precarga aplicado a ambos modelos es el recomendado, no hay diferencias entre los dos pilares.

The purpose of this study was to determine the mechanical behavior between Zimmer® zirconium implant abutments with and without a titanium washer at their base, by using the finite element analysis (FEA). Materials and Methods: two models of a zirconium abutment on implants were designed, composed of a Zimmer® titanium implant a fixation screw, cortical and cancellous bone, and the ceramic crown of an upper central incisor. An oblique force was applied with a magnitude of 200N, ascending in a scale of 200N until any of the components of the model exhibited a nonlinear behavior. Von Mises stresses were calculated for each element. Results: No significant differences on von Mises stresses were observed between the abutments with and without a titanium washer (280, 1MPa with a titanium washer, and 280, 4 MPa without it) but differences were found at the fixation screw and the implant: the stresses were lower in the model with a titanium washer (474MPa vs 576,7MPa). Both the bone and the crown exhibited non linearity at 600N, the implant and the screw at 1000N, and both zirconium abutments at 1400N. Conclusions: When the preload stress applied to both models is the adequate, no mechanical behavior differences between the abutments occur.

Este estudo procurou determinar o comportamento mecânico entre pilares anel Zimmer® Zircônio Titanium na base e sem ela, usando o método de análise de elementos finitos Métodos: Dois modelos de zircônia pilar no implante projetados também formadas por um implante Titanium parafuso de ligação Zimmer®, osso cortical e osso esponjoso e uma coroa de cerâmica de um incisivo central superior. A força foi aplicada com um ângulo com uma amplitude de 200N, 200N escala crescente, até um elemento excedido o limite de proporcionalidade. Esforços von Mises, foram calculados para cada elemento. Resultados: Não foram observadas diferenças na magnitude dos esforços von Mises entre Titanium anel de encosto sem ele; (280,1 MPa Titanium anel, 280,4 MPa sem ele), mas no parafuso eo implante, com esforços menores para o modelo com anel de titânio (474 vs 576,7 MPa 15 MPa). Osso e coroa não-linearidade informou a 600N, implante de parafuso 1000N e zircônio dois pilares 1400N. Conclusão: Quando a pré-carga esforço aplicado para ambos os modelos é recomendado, não há diferenças entre os dois pilares.

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INTRODUCTION: The aim of this study was to evaluate the flexibility and torsional stiffness of a controlled memory (CM) nickel-titanium (NiTi) file and compare its mechanical responses with those of a superelastic NiTi file with the same geometry using finite element simulation. METHODS: A commercially available instrument with a tip size of 30 and a 0.06 taper was selected for this study. The geometric model for finite element analysis was generated by micro-computed tomographic scanning, and the data for the constitutive model of controlled memory NiTi were obtained from the literature. The numeric analysis was performed in ABAQUS (SIMULIA, Providence, RI) with boundary conditions that were based on the ISO 3630-1 specification. RESULTS: The CM NiTi file exhibited the least bending moment and maximum stress value (523 MPa) under 45° bending simulation. However, the least torsional stiffness was calculated for this same instrument. CONCLUSIONS: The higher flexibility and potential fatigue resistance of the CM NiTi files were confirmed, indicating that this new technology represents an improvement in the mechanical behavior of the rotary NiTi files.

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