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Resumen: Introducción: El pie cavo es una patología musculoesquelética con un aumento del arco medial del pie. La etiología del pie cavo aún es incomprensible, está relacionada con afecciones neurológicas, enfermedad de Charcot-Marie-Tooth, ataxia de Friedreich y parálisis cerebral. El objetivo de esta investigación fue analizar la distribución de la presión plantar en atletas jóvenes con pie cavo. Material y métodos: Se reclutaron 83 atletas jóvenes de entre nueve y 20 años de edad, que presentaban patología de pie cavo. La masa y el promedio de altura fueron 56.9 ± 12.36 kg y 1.61 ± 0.10 m, respectivamente. La distribución de la presión plantar de los pies se registró durante condiciones estáticas. Se compararon las presiones del antepié y el retropié. Resultados: La distribución de la presión plantar se categorizó en tres grupos. En el primer grupo los participantes presentaron mayor presión en la parte anterior del pie; en el segundo grupo los atletas mostraron una presión similar en la región posterior y anterior de los pies y en el último los sujetos revelaron una mayor presión en el retropié. Para ser considerado en uno de los tres grupos, la diferencia de presión entre la parte posterior y anterior del pie se estableció en 16%. Conclusión: Muchos trastornos musculoesqueléticos en el cuerpo humano son de origen biomecánico y están relacionados con la anatomía del pie. El pie cavo es una patología con alta prevalencia en atletas y está relacionada con las fuerzas mecánicas sobre los pies en condiciones dinámicas.
Abstract: Introduction: The cavus foot is a musculoskeletal pathology with an increase of the medial arch of the concavity of the foot. The etiology of the cavus foot is still enigmatic, it is related with neurologic conditions, Charcot-Marie-Tooth disease, Friedreich's ataxia, and cerebral palsy. The aim of this research was to analyze the plantar pressure distribution of the feet on young athletes with cavus foot. Material and methods: Eighty-three young athletes between nine and 20 years old, that presented cavus feet pathology were recruited. The mass and height average were 56.9 ± 12.36 kg and 1.61 ± 0.10 m respectively. Plantar pressure distribution of the feet was recorded during static conditions. The hindfoot and forefoot pressure were compared in each foot. Results: The plantar pressure distribution were categorized in three groups. In the first group the participants presented higher pressure in the hindfoot than forefoot, in the second group, the athletes showed similar pressure in the posterior and anterior region of the feet and in the last one, the subjects revealed higher pressure in the forefoot. To be considered in one of the three groups, the difference of pressure between the posterior and anterior part of the foot was established at 16%. Conclusion: Many musculoskeletal disorders in the human body are biomechanical in origin and related with foot anatomy. The cavus foot is a pathology with high prevalence in athletes and it is related with the mechanical forces over the feet during dynamic conditions.
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Objective：This study aimed to evaluate the mechanical strength of immobilized osteopenia using a fixed limb rat model.Methods：Eight-week-old specific-pathogen-free male Wistar rats were divided into two groups, a control group (n＝32) and an immobilized group (n＝32). The hind limbs of the immobilized group were fixed using an orthopedic cast, and the fixation periods were set for 1, 4, 8, and 12 weeks. Feeding and weight-bearing were permitted. After each fixation period, the length of the right femoral bone was measured, and three-point bending at the midshaft and uniaxial compression test at the distal metaphysis were performed with a universal material testing apparatus. The maximum force and breaking force in the bending test and ultimate load in the compression test were statistically analyzed.Results：The values of the maximum force and breaking force in the immobilized group were significantly lower than those in the control group at 4, 8, and 12 weeks (p＜0.05). The ultimate load of the distal metaphysis in the immobilized group decreased from 1 week after fixation, and the gap with the control group widened as the fixation period extended.Conclusion：The results of this study indicate that bone weakness caused by immobilized osteopenia arises after 1 week in the metaphysis and after 4 weeks in the midshaft.
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Objective：This study aimed to evaluate the mechanical strength of immobilized osteopenia using a fixed limb rat model.Methods：Eight-week-old specific-pathogen-free male Wistar rats were divided into two groups, a control group (n＝32) and an immobilized group (n＝32). The hind limbs of the immobilized group were fixed using an orthopedic cast, and the fixation periods were set for 1, 4, 8, and 12 weeks. Feeding and weight-bearing were permitted. After each fixation period, the length of the right femoral bone was measured, and three-point bending at the midshaft and uniaxial compression test at the distal metaphysis were performed with a universal material testing apparatus. The maximum force and breaking force in the bending test and ultimate load in the compression test were statistically analyzed.Results：The values of the maximum force and breaking force in the immobilized group were significantly lower than those in the control group at 4, 8, and 12 weeks (p＜0.05). The ultimate load of the distal metaphysis in the immobilized group decreased from 1 week after fixation, and the gap with the control group widened as the fixation period extended.Conclusion：The results of this study indicate that bone weakness caused by immobilized osteopenia arises after 1 week in the metaphysis and after 4 weeks in the midshaft.
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@#Hydrofluoric acid is a common surface treatment agent for glass ceramic restorations before bonding. However, the use of hydrofluoric acid has a high safety risk, so the search for hydrofluoric acid substitutes has been a research hotspot. Tetrabutylammonium dihydrogen trifluoride is a kind of fluoride, whose chemical activity is lower than that of hydrofluoric acid, so it’s safer, and the surface morphology changes on glass ceramics caused by it are smaller and more superficial. At present, the vast majority of laboratory studies and clinical case reports indicate that the mechanical strength and bonding strength of glass ceramics treated with tetrabutylammonium dihydrogen trifluoride can meet the clinical requirements. In the future, according to the research results, the performance of porcelain surface treatment agents containing tetrabutylammonium dihydrogen trifluoride can be further improved, and more hydrofluoric acid substitutes may be developed. In this review, the research progress of tetrabutylammonium dihydrogen trifluoride as a substitute for hydrofluoric acid is reviewed in terms of the influence of the surface morphology, mechanical strength, and bonding strength of glass ceramics.
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@#Bone tissue engineering, as an emerging method for the treatment of jaw defects caused by oral and maxillofacial trauma, inflammation, tumors and other diseases, has been a research hotspot due to its advantages of wide sources of materials, low risk of immune rejection and personalized treatment. However, due to functional activities such as chewing and expression in the oral and maxillofacial regions, the mechanical strength of scaffolds is highly required. A single component of scaffolds can not fully meet the requirements of oral and maxillofacial bone defect repair. In this paper, the methods of strengthening the mechanical strength of jaw bone tissue engineering scaffolds are summarized by summarizing the research on strengthening the mechanical strength of scaffolds in recent years. A review of the literature showed that, composite modification, crosslinking, coating, bionic scaffolding and other new processing methods have been used to enhance the mechanical strength of scaffolds. Among these studies, research on compound modification occurred the earliest. Although this process is simple, other substances have been introduced to increase the number of degradation products, and the compounding ratio needs to be adjusted. The crosslinking method has the risk of cytotoxicity due to the use of crosslinking agents; the coating method does not change the original structure and only changes the surface modification; however, it can be better utilized if the problem of stress concentration between interfaces is solved. Biomimetic scaffolds and microregulatory scaffolds are emerging technologies in recent years that can improve the internal molecular arrangement of materials, thus enhancing mechanical strength. Therefore, on the basis of perfecting the traditional method, future research will focus on new nanoscale materials, bionic scaffolds and new methods for the precise control of scaffold microstructure.
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Current biomechanical research of dental implants focuses on the mechanical damage and enhancement mechanism of the implant-abutment interface as well as how to obtain better mechanical strength and longer fatigue life of dental implants. The mechanical properties of implants can be comprehensively evaluated by strain gauge analysis, photo elastic stress analysis, digital image correlation, finite element analysis, implant bone bonding strength test, and measurement of mechanical properties. Finite element analysis is the most common method for evaluating stress distribution in dental implants, and static pressure and fatigue tests are commonly used in mechanical strength test. This article reviews biomechanical research methods and evaluation indices of dental implants. Results provide methodology guidelines in the field of biomechanics by introducing principles, ranges of application, advantages, and limitations, thereby benefitting researchers in selecting suitable methods. The influencing factors of the experimental results are presented and discussed to provide implant design ideas for researchers.
Subject(s)
Biomechanical Phenomena , Computer Simulation , Consensus , Dental Abutments , Dental Implant-Abutment Design , Dental Implants , Dental Prosthesis Design , Dental Stress Analysis , Finite Element Analysis , Stress, MechanicalABSTRACT
OBJECTIVES: To examine the effects of whole body vibration (WBV) on bone properties in growing rats, and to explore the optimal conditions for enhancing bone properties. METHODS: Thirty-six 4-week-old male rats were divided into 1 control and 5 experimental groups. Each experimental group underwent WBV at 15, 30, 45, 60, and 90 Hz (0.5 g, 15 min/d, 5 d/wk) for 8 weeks.We measured bone size, muscle weight and bone mechanical strength of the right tibia. Trabecular bone mass and trabecular bone microstructure (TBMS) of the left tibia were analyzed by micro-computed tomography. Serum levels of bone formation/resorption markers were also measured. RESULTS: WBV at 45 Hz and 60 Hz tended to enhance trabecular bone mass and TBMS parameters. However, there was no difference in maximum load of tibias among all groups. Serum levels of bone resorption marker were significantly higher in the 45-Hz WBV group than in the control group. CONCLUSIONS: WBV at 45–60 Hz may offer a potent modality for increasing bone mass during the period of rapid growth. Further studies are needed to explore the optimal WBV conditions for increasing peak bone mass and TBMS parameters. WBV modality may be a potent strategy for primary prevention against osteoporosis.
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Animals , Humans , Male , Rats , Bone Resorption , Osteoporosis , Primary Prevention , Tibia , VibrationABSTRACT
Abstract This study evaluated the effect of the accelerated artificial aging (AAA) on feldspar ceramic strength and the reinforcing effect promoted by adhesive cementation with resin luting agent. One hundred twenty feldspar ceramic disks were obtained. Sixty disks were acid-etched, silanized, and coated with an experimental resin luting agent simulating the adhesive luting procedures. Four groups were created (n=30): uncoated ceramic (control group), uncoated ceramic submitted to AAA, ceramic coated with resin luting agent, and coated ceramic submitted to AAA. Biaxial flexural testing with ball-on-ring setup was carried out. Biaxial flexural strength (s bf , MPa), characteristic strength (s 0 , MPa), and Weibull modulus (m) were calculated for axial positions z=0 (ceramic surface) and z=−t2 (luting agent surface). Data of s bf at positions z=0 and z=-t2 were separately submitted to statistical analyses (a=0.05). The uncoated ceramic submitted to AAA had no significant difference in s bf and s 0 compared with the control group. Resin coating of the ceramic increased s bf and s 0 at z=0. The AAA increased the s bf and s 0 for the resin-coated ceramic specimens at z=0 and also the s 0 at axial position z=-t2. The structural reliability at z=0 and z=-t2 was not influenced by the variables tested. In conclusion, resin coating improved the mechanical strength of the feldspar ceramic. The AAA procedure was not effective in aging the uncoated or resin-coated feldspar ceramic specimens.
Resumo Este estudo avaliou o efeito do envelhecimento artificial acelerado (EAA) na resistência da cerâmica feldspática e o reforço promovido pela cimentação adesiva com cimento resinoso. Cento e vinte discos de cerâmica feldspática foram obtidos. Sessenta discos foram condicionados com ácido, silanizados, e recobertos com um cimento resinoso experimental simulando os procedimentos de cimentação adesiva. Quatro grupos foram criados (n=30): cerâmica sem recobrimento (grupo controle), cerâmica sem recobrimento submetida ao EAA, cerâmica recoberta com cimento resinoso, cerâmica recoberta com cimento resinoso submetida ao EAA. O teste de resistência à flexão biaxial foi realizado utilizando o dispositivo pistão-anel. Resistência à flexão biaxial (s fb , MPa), resistência característica (s 0 , MPa), e módulo de Weibull (m) foram calculados para as posições axiais z=0 (superfície da cerâmica) e z=−t2 (superfície do cimento). Os dados de s fb em z=0 e z=−t2 foram submetidos a análises estatísticas separadamente (a=0,05). A cerâmica não recoberta submetida ao EAA não teve diferença significante na s fb e s 0 comparada com o grupo controle. O recobrimento com cimento resinoso da cerâmica aumentou a s fb e s 0 em z=0. O EAA aumentou a s fb e s 0 para os espécimes de cerâmica recobertos com cimento resinoso em z=0 e também a s 0 em z=−t2. A confiabilidade em z=0 e z=−t2 não foi influenciada pelas variáveis testadas. Concluindo, o recobrimento com cimento resinoso melhorou a resistência mecânica da cerâmica feldspática. O procedimento de EAA não foi efetivo em envelhecer os espécimes de cerâmica feldspática recobertos ou não com cimento resinoso.
Subject(s)
Materials Testing , Potassium Compounds/chemistry , Resin Cements/chemistry , Dental Cements/chemistry , Dental Porcelain/chemistry , Aluminum Silicates/chemistry , Dental Bonding , Composite Resins/chemistry , Dental Stress AnalysisABSTRACT
As a novel transdermal drug delivery technology,microneedles has some advantages including high efficiency and safety over other drug administration routes. The skin puncture performance is the premise and key for microneedles to deliver drugs. Based on the mechanical strength of the microneedles and the puncture effect of the skin, this review summarized the current evaluation methods of puncture performance. These methods were described here such as fracture strength measurement, pressure-displacement performance testing, organic dye staining, transepidermal water loss, electrical impedance method, histological sections, confocal microscopy and optical coherence tomography. The scope of application, advantages and disadvantages of various methods were analyzed, which provide references for other researchers to choose suitable evaluation method of microneedles puncture performance.
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The purpose of this study is to correlate the material properties of TiZr alloy material (Roxolid) and the mechanical strength of the implant fixture (BLT) through the maximum compressive load test and the fatigue test. Implant samples were purchased with BLT (Roxolid, Straumann, Switzerland) and Octa1 (cold-worked, Megagen Implant, Korea) fixtures made of two materials (TiZr and cold-worked Ti Grade 4). After the maximum compressive load test, the test specimens were analyzed with a optical microscope to confirm the fracture pattern. After the fatigue test, the samples that passed 5 million cycles were analyzed for the precision fit using a scanning electron microscope. Data were analyzed using Student's t-test (α=0.05). In the compressive load test, the small diameter (3.3 mm) implants with the same length and the common diameter (4.1 mm) implants had fracture or bending regardless of the material in both the test and control groups. The fatigue load showed the same results without significance and the gap between the fixture and abutment interface was within 10 µm in both the test and control groups in the precision fit test. There was no statistically significant difference in the maximum compressive load and fatigue test for the comparison of mechanical strength between two systems (BLT vs. Octa1) with same diameter and length, similar shapes and connections.
Subject(s)
Alloys , FatigueABSTRACT
Abstract This study investigated the in vitro performance of the commercial bis-acryl composite resins Systemp C&B II (SYS, Ivoclar Vivadent), Protemp 4 (PT4, 3M ESPE), Structur 2C (ST2, Voco) and ProviPlast (PVP, Biodinamica). Characterization involved optical (color stability, translucency parameter, fluorescence), surface (roughness, morphology and elemental composition), physical-chemical (viscosity, polymerization kinetics) and mechanical analyses (Poisson ratio, biaxial flexural strength, flexural modulus). Most tests were carried out after 24 h, but optical and mechanical analyses were carried out after storage in water at 37 °C for 1, 15, and 30 days. Data were statistically analyzed (a=0.05). Most results were material dependent. SYS and PT4 showed stability in color and translucency over time. All materials had similar or higher fluorescence than human enamel. SC2 and PVP showed rougher surfaces than the other bis-acryl composites. Smaller filler particles were observed on the surface of PT4 and PVP compared with the coarser particles from ST2 and SYS. Viscosity readings indicated a thixotropic behavior for all tested materials. SYS had the lowest and PT4 the highest degree of C=C conversion after 10 min. In the polymerization kinetics, PT4 had the highest maximum polymerization rate and reached earlier the transition between polymerization autoacceleration and autodeceleration. PT4 and SYS had significantly higher flexural strength and modulus than ST2 and PVP for most storage times. Results for Poisson ratio varied between materials. Longer storage periods were generally associated with higher frequency of catastrophic failures in the flexural tests. In conclusion, the performance of bis-acryl composite resins varied largely among materials.
Resumo Este estudo investigou o desempenho in vitro de quatro resinas compostas bisacrílicas comerciais: Systemp C&B II (SYS, Ivoclar Vivadent), Protemp 4 (PT4, 3M ESPE), Structur 2C (ST2, Voco) e ProviPlast (PVP, Biodinamica). A caracterização envolveu análises ópticas (estabilidade de cor, parâmetro de translucidez, fluorescência), de superfície (rugosidade, morfologia e composição elementar), físico-químicas (viscosidade, cinética de polimerização) e mecânicas (razão de Poisson, resistência à flexão biaxial, módulo de elasticidade). A maioria dos testes foram realizados após 24 h, enquanto análises ópticas e mecânicas foram realizadas após armazenamento em água a 37 °C por 1, 15 e 30 dias. Os dados foram analisados estatisticamente (a=0,05). Grande parte dos resultados foi dependente do material. SYS e PT4 mostraram estabilidade de cor e translucidez ao longo do tempo. Todos os materiais apresentaram fluorescência similar ou maior que o esmalte humano. SC2 e PVP apresentaram superfícies mais rugosas que os outros materiais. Menores partículas de carga foram observadas na superfície de PT4 e PVP comparadas às partículas mais irregulares de ST2 e SYS. As leituras de viscosidade indicaram comportamento tixotrópico para todos os materiais testados. SYS teve a menor e PT4 o maior grau de conversão de C=C após 10 min. Na cinética de polimerização, PT4 teve a maior taxa máxima de polimerização e atingiu mais cedo a transição entre autoaceleração e autodesaceleração da polimerização. PT4 e SYS apresentaram resistência à flexão e módulo de elasticidade significativamente maiores que ST2 e PVP na maioria dos períodos de armazenamento. Resultados da razão de Poisson variaram entre os materiais. Períodos mais longos de armazenamento foram em geral associados a maior frequência de falhas catastróficas nos testes de flexão. Em conclusão, o desempenho das resinas compostas bisacrílicas variou amplamente entre os materiais.
Subject(s)
Humans , Composite Resins , Dental Restoration, Temporary , Dental Enamel/chemistry , Dental Stress Analysis , Fluorescence , Kinetics , Microscopy, Electron, Scanning , Poisson Distribution , Polymerization , Surface Properties , ViscosityABSTRACT
Aim To investigate the effect of curcumin against high-fat-diet induced C57BL/6J mice bone changes and the correlation between the expression of cathepsin K and curcumin.Methods Curcumin treated C57BL/6J mice had been on high fat diet for 12 weeks.The HE, Alizarin red S staining and Safranin O/fast green staining of femur were employed to evaluate bone microstructure, bone metabolism and bone development.The expressions of cathepsin K were assessed by Western blot and immunohistochemical staining.Results Histopathological results showed that curcumin could improve the destruction of trabecular bone structure, cartilage development and bone calcification.Biomechanical results proved that curcumin could improve the bone strength of the type 2 diabetic mice induced by high fat.The results of immunohistochemistry and Western blot assay indicated that curcumin could significantly inhibit the expression of cathepsin K in bone tissues of mice.Conclusion Curcumin can increase bone strength, improve bone microstructure, and enhance the degree of bone calcification, which may be achieved by inhibiting the expression of cathepsin K.
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The focus of this study was to test the fracture resistance of upper arch dental retainers, made by two different manipulation techniques of acrylic resin. 84 plates Wraparound type retainers were made by two different manipulation techniques forming two groups (n = 42): Group 1 (Addition Technique) and Group 2 (Pressing Technique). All the retainers were duly shaped in U form with the aid of standardized plaster cast models. During the confection process the standardizing of the retainers was conducted carefully regarding their thickness and dimensions with the aid of a gauge and a straight caliper. After confection they remained immersed in water for 24 hours at 37°C. Next, they were tested through mechanical compression until fracture in a universal mechanical testing machine. Data were analyzed by Student's t test. The significance level was set at 5% ( = 0.05). It was found that the average was of 79.12 N for Group 1 and of 77.07 N for Group 2 with a standard deviation of 17.30 N and 16.31, respectively, showing that there is no significant difference in resistance for the retainers when made through any of the two methods (P=0.788). The addition and pressure techniques of acrylic resin do not influence the resistance to compression of the upper dental retainers.
O foco deste estudo foi testar a resistência à fratura de retentores odontológicos do arco superior, feito por duas diferentes técnicas de manipulação de resina acrílica. 84 placas de retentores tipo Wraparound foram feitas por duas diferentes técnicas de manipulação que formam dois grupos (n = 42): Grupo 1 (técnica de adição) e Grupo 2 (técnica de prensagem). Todos os retentores foram devidamente moldado em forma de U, com o auxílio de modelos de gesso padronizados. Durante o processo de confecção a padronização dos retentores foi conduzida cuidadosamente em relação à sua espessura e dimensões, com o auxílio de um medidor e um compasso de calibre linear. Após a confecção eles permaneceram imersos em água por 24 horas a 37 °C. Em seguida, eles foram testados através de compressão mecânica até a fratura em uma máquina universal de ensaios mecânicos. Os dados foram analisados pelo teste t de Student. O nível de significância foi de 5% ( = 0,05). Verificou-se que a média foi de 79,12 N para o Grupo 1 e de 77,07 N para o Grupo 2, com um desvio padrão de 17,30 N e 16,31, respectivamente, indicando que não há diferença significativa na resistência para os retentores, quando feita através de qualquer um dos dois métodos (P = 0,788). As técnicas de adição e pressão de resina acrílica não influenciaram a resistência à compressão dos retentores dentárias superiores.
Subject(s)
Orthodontics , Acrylic Resins , Orthodontic RetainersABSTRACT
Aims: The objective of this study was to synthesize and characterize the poly (acrylic acid) or PAA with different molecular architectures, use these polymers to formulate the cements with glass fillers, and evaluate the mechanical strengths of the formed cements. Materials and Methods: The novel poly (acrylic acid)s with different molecular architectures were synthesized via ATRP technique. The reaction kinetics was studied. The formed cements were evaluated using compression, diametral compression, and 3- point bending, fracture toughness, knoop hardness, and wear resistance tests. The experimental cement was also evaluated for its in vitro biocompatibility. Results: The results showed that either hyperbranched or star-hyperbranched polymer synthesis proceeds more slowly at the early stage but accelerates more quickly at the later stage than the star-shaped polymer synthesis. The higher the arm number and initiator concentration, the faster the ATRP reaction. It was also found that the higher the arm number and branching that the polymer had, the lower the viscosity of the polymer aqueous solution and the lower the mechanical strengths of the formed cement exhibited. The mechanical strengths of all three experimental glass-ionomer cements were very similar to each other but much higher than those of Fuji II LC. The aging study showed that all the experimental cements increased their CS continuously during 30 days, unlike Fuji II LC. This novel cement system was proven to be in vitro biocompatible because it showed no any noticeable cytotoxicity to human dental pulp cells and mouse 3T3 mouse fibroblasts.
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Aim: Present study includes the development and evaluation of superporous hydrogel composites of acrylamide using starch silicone dioxide coprecipitate (SSC) as composite agent. Methodology: Gas blowing method was used for synthesis of superporous hydrogels. Different ingredients were mixed in specified amount in test tube and foaming agent was added at last. Simultaneous foaming and gelation lead to formation of porous hydrogel networks. Effect of different treatments (acetone dehydration and simulated gastric fluid (SGF) treatment) and drying conditions on the porous structure was evaluated. The prepared superporous hydrogels were evaluated for density, porosity, equilibrium swelling ratio, equilibrium swelling time, mechanical strength, scanning electron microscopy studies. The pure drug (Verapamil Hydrochloride) mixed with Carbopol 934 (1:0.5 and 1:1 ratio) was loaded into the selected batches of SPHC using in situ method of drug loading (drug added directly into the reaction mixture). The in vitro drug release was carried out using USP II dissolution apparatus. Results: Acetone dehydrated superporous hydrogel composites were observed as better floating devices due to least density and maximum porosity values. Maximum swelling ratio was found in case of oven dried conventional superporous hydrogel and superporous hydrogel composites with equilibrium swelling time of more than 25 min. On the other hand, acetone dehydrated SPH showed less equilibrium swelling ratio with equilibrium swelling time of 5-10 min. Minimum swelling ratio was observed in case of SGF treated hydrogels with equilibrium swelling time of 15-19 min. Mechanical strength was improved by addition of starch silicone dioxide coprecipitate as composite agent. SGF treatment also leads to enhanced mechanical strengthbut compromised swelling characteristics. SEM images showed uniformity in pore structure in case of acetone dehydrated hydrogels. Acetone dehydrated SPHC showed sustained drug release behavior with 71.14% and 57.84% of verapamil released in 12 h in the batches with Drug: Carbopol 934ratio of (1:0.5 and 1:1) respectively. Conclusion: Acetone dehydrated SPHC were found to be promising formulations with sufficient swelling and mechanical properties for achieving sustained drug delivery.
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OBJECTIVE: To study the influence of konjac glucomannan (KGM) on properties of superporous hydrogel (SPH).
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BACKGROUND:Glass ionomer cements have been gradual y employed in many aspects of dental clinical field. However, low mechanical strength and antibacterial effect restrict its further applications. OBJECTIVE:To proportional y explore the effects of titanium dioxide nanoparticles on the mechanical strength and antibacterial effect of traditional glass ionomer cements. METHODS:Base on different mass fractions of titanium dioxide nanoparticles in glass ionomer cements, al the glass ionomer cement samples were divided into control group (no titanium dioxide nanoparticles), low titanium dioxide group (containing 3%titanium dioxide nanoparticles), medium titanium dioxide group (containing 6%titanium dioxide nanoparticles), and high titanium dioxide group (containing 9%titanium dioxide nanoparticles). A universal material testing machine and a hardness tester were used to examine flexural strength, compressive strength, and surface hardness of glass ionomer cement samples, respectively. Glass ionomer cement samples were immerged into the artificial saliva, and fluoride release was measured by using a fluoride ion selective electrode. The direct contact test was used to investigate antibacterial effect of glass ionomer cement samples towards Streptococcus mutans. RESULTS AND CONCLUSION:Compared with the control group, few titanium dioxide nanoparticles (low and medium titanium dioxide group) could significantly improve flexural strength, compressive strength and surface hardness of glass ionomer cement samples (P<0.05), and high titanium dioxide nanoparticles (high titanium dioxide group) significantly decreased flexural strength, compressive strength and surface hardness (P<0.05). The introduction of titanium dioxide nanoparticles had little effect on fluorine release behavior of glass ionomer cement samples, and greatly improved antibacterial effect of glass ionomer cement samples towards Streptococcus mutans.
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Introduction: Bone strength is influenced by a number of different determinants, such as mass, size, geometry and also by the intrinsic material properties of the tissue. Aims: The structure and mechanical properties of the femur were analyzed in aged (14 mo-old) animals submitted to hindlimb unloading (HU) for 21 days. Methods: Twenty Wistar rats were randomly divided into Control and HU groups and the femur was submitted to dual X ray absorptiometry (DXA), DIGORA radiographic density, mechanical compression testing and Knoop microhardness analyse in cortical and cancellous bone. Results: Femurs from HU group presented significantly lower failure load, decreased bone mineral density (BMD)/bone mineral content (BMC) in whole bone; proximal/distal epiphysis and middiaphyseal cortical bone measured by DXA were similar in the two groups; radiographic density from areas in proximal epiphysis was significantly lower in HU group, and microhardness measured at periosteal and endosteal levels were also significantly diminished in HU compared with Control group. Conclusion: Disuse induced damage in the trabecular femoral bone architecture with decisive effect on the head and trochanteric fossa, which became weaker. Bone diaphyseal cortical hardness also suffered effect of unloading, probably related to osteocyte/osteoblast activity.
Subject(s)
Animals , Male , Rats , Absorptiometry, Photon , Bone and Bones , Femur/anatomy & histology , Femur/metabolism , Biomechanical Phenomena , Densitometry , Femur/physiopathology , Rats, WistarABSTRACT
Na Odontologia, ao se confeccionar peças restauradoras dentárias, pela técnica indireta, o processo mais rotineiramente empregado utiliza um modelo de gesso, obtido a partir de um molde de elastômero, tomado de um dente preparado. Vários fatores podem influenciar na boa precisão de ajustes destas peças como o escoamento do material de vazamento dentro da moldagem, a compatibilidade do material de vazamento com o da moldagem, o tempo de presa, a estabilidade dimensional, a resistência mecânica do material quando da separação moldagem/modelo, a resistência a abrasão e a fidelidade de reprodução de detalhes. Materiais foram introduzidos na odontologia para utilização na confecção de troquéis no intuito de minimizar as desvantagens do gesso, como baixa resistência a abrasão e ligeira expansão de presa. Dentre eles os troquéis metalizados e as resinas epóxicas, que tem vantagens em relação às propriedades mecânicas, porém o primeiro exige técnica demorada e de alto custo e o segundo apresenta contração. O presente trabalho se propõe a testar uma nova composição de poliéster insaturado com estireno adicionado ao carbonato de cálcio em diferentes proporções (10, 20, 30, 40, 50, 60 e 70%) e compará-la ao gesso tipo IV e a resina epoxídica com óxido de alumínio, através de ensaios mecânicos, de abrasão e de alteração dimensional, para avaliar a possibilidade de sua utilização como material de confecção de troquéis para a construção de restaurações indiretas. Para caracterização dos materiais foram feitas análises de espectrometria no infravermelho, Calorimetria de varredura diferencial, termogravimétrica e Microscopia eletrônica de varredura. O compósito a base de poliéster insaturado com 50% de carbonato de cálcio se mostrou viável para utilização como material para troquel. Quando comparado aos materiais de controle mostrou propriedades mecânicas próximas as da resina epoxídica e bem superiores ao gesso, resistência a abrasão superior ao gesso ...
In dentistry, the most commonly used procedure to manufacture indirect dental restorations uses a cast of type IV stone. This cast is made from an elastomeric impression of a prepared tooth. Many factors may influence the accuracy of adaptation of these restorations, such as the flow of the pouring material into the mold, the compatibility between the pouring and the impression materials, the setting time, the dimensional stability, the mechanical strength of the material during the mold / cast separation, the abrasion resistance and fidelity to reproduce details. Materials were introduced for preparing dies in order to minimize the disadvantages of the stone, such as its low resistance to abrasion and slight expansion of setting. These materials include metal-plated dies and epoxy resins, which have advantages concerning mechanical properties. However, the first one has a time-consuming technique and requires high costs while the second material shows shrinkage. This study tested a new composition of unsaturated polyester with styrene added to calcium carbonate in different proportions (10, 20, 30, 40, 50, 60 and 70%) and compared it to the type IV stone and to the epoxy resin with aluminum oxide. This comparison was made by mechanical, abrasion and dimensional changes tests in order to evaluate the possibility of using it as material for dies in the process of construction of indirect restorations. The materials were characterized using the analysis of the infrared spectrometry, differential scanning calorimetry, thermogravimetric and scanning electron microscopy. The composite based on unsaturated polyester with 50% calcium carbonate (P5) was considered viable as material for dies. When it was compared to the control materials the following results were found: a) the mechanical properties of P5 are similar to those ones of the epoxy resin and well above the stone ones; b) the abrasion resistance of this new material is lower in relation to ...
Subject(s)
Calcium Carbonate , Dental Impression Materials , Dental Restoration, Permanent , Polyesters , Calorimetry , Compressive Strength , Mass Spectrometry , Materials Testing , Microscopy, Electron, Scanning , Tensile Strength , Thermogravimetry , Tooth AbrasionABSTRACT
Na Odontologia, ao se confeccionar peças restauradoras dentárias, pela técnica indireta, o processo mais rotineiramente empregado utiliza um modelo de gesso, obtido a partir de um molde de elastômero, tomado de um dente preparado. Vários fatores podem influenciar na boa precisão de ajustes destas peças como o escoamento do material de vazamento dentro da moldagem, a compatibilidade do material de vazamento com o da moldagem, o tempo de presa, a estabilidade dimensional, a resistência mecânica do material quando da separação moldagem/modelo, a resistência a abrasão e a fidelidade de reprodução de detalhes. Materiais foram introduzidos na odontologia para utilização na confecção de troquéis no intuito de minimizar as desvantagens do gesso, como baixa resistência a abrasão e ligeira expansão de presa. Dentre eles os troquéis metalizados e as resinas epóxicas, que tem vantagens em relação às propriedades mecânicas, porém o primeiro exige técnica demorada e de alto custo e o segundo apresenta contração. O presente trabalho se propõe a testar uma nova composição de poliéster insaturado com estireno adicionado ao carbonato de cálcio em diferentes proporções (10, 20, 30, 40, 50, 60 e 70%) e compará-la ao gesso tipo IV e a resina epoxídica com óxido de alumínio, através de ensaios mecânicos, de abrasão e de alteração dimensional, para avaliar a possibilidade de sua utilização como material de confecção de troquéis para a construção de restaurações indiretas. Para caracterização dos materiais foram feitas análises de espectrometria no infravermelho, Calorimetria de varredura diferencial, termogravimétrica e Microscopia eletrônica de varredura. O compósito a base de poliéster insaturado com 50% de carbonato de cálcio se mostrou viável para utilização como material para troquel. Quando comparado aos materiais de controle mostrou propriedades mecânicas próximas as da resina epoxídica e bem superiores ao gesso, resistência a abrasão superior ao gesso...
In dentistry, the most commonly used procedure to manufacture indirect dental restorations uses a cast of type IV stone. This cast is made from an elastomeric impression of a prepared tooth. Many factors may influence the accuracy of adaptation of these restorations, such as the flow of the pouring material into the mold, the compatibility between the pouring and the impression materials, the setting time, the dimensional stability, the mechanical strength of the material during the mold / cast separation, the abrasion resistance and fidelity to reproduce details. Materials were introduced for preparing dies in order to minimize the disadvantages of the stone, such as its low resistance to abrasion and slight expansion of setting. These materials include metal-plated dies and epoxy resins, which have advantages concerning mechanical properties. However, the first one has a time-consuming technique and requires high costs while the second material shows shrinkage. This study tested a new composition of unsaturated polyester with styrene added to calcium carbonate in different proportions (10, 20, 30, 40, 50, 60 and 70%) and compared it to the type IV stone and to the epoxy resin with aluminum oxide. This comparison was made by mechanical, abrasion and dimensional changes tests in order to evaluate the possibility of using it as material for dies in the process of construction of indirect restorations. The materials were characterized using the analysis of the infrared spectrometry, differential scanning calorimetry, thermogravimetric and scanning electron microscopy. The composite based on unsaturated polyester with 50% calcium carbonate (P5) was considered viable as material for dies. When it was compared to the control materials the following results were found: a) the mechanical properties of P5 are similar to those ones of the epoxy resin and well above the stone ones; b) the abrasion resistance of this new material is lower in relation to...