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1.
Braz. dent. j ; 32(4): 55-61, July-Aug. 2021. tab, graf
Article in English | LILACS, BBO | ID: biblio-1345512

ABSTRACT

Abstract The purpose of this in vitro study was to evaluate the force decrease of different elastomeric chains after different times: initial, 10 minutes, 1 day, 28 days and after mechanical brushing. Twenty orthodontic elastomeric chains segments were utilized for each commercial brand. Initially, the elastomeric chain of 15mm long were immediate stretched up to 20 mm in an Instron and the force was measured in gf. After all specimens were placed stretched on rectangular acrylic jigs with distance of 20 mm, immersed in deionized water at 37oC for 10 minutes and the force (gf) was measured again. Five test measurements of remaining force were made at the following time intervals: initial, 10 minutes, 1 day, 28 days and mechanical brushing. After 28 days, the acrylic plates with the specimens were adapted in the mechanical brushing machines (MSCT 3) and the elastomeric chains were submitted to mechanical brushing and the force (gf) measure again. The force (gf) was submitted to mixed-model ANOVA and Sidak post-hoc test (α=0.05). A statistically significant reduction in the force was found for all orthodontic elastomeric chain types after 1 day, 28 days and mechanical brushing (p<0.05). Morelli and 3M Unitek elastomeric chains showed significantly higher force than Abzil and GAC (p<0.05) after 1 day, 28 days and mechanical brushing. In conclusion, the force delivered by all elastomeric chains decayed rapidly over time. Morelli and 3M Unitek elastomeric chains consistently had a significantly greater force after mechanic brushing, while GAC the lowest.


Resumo O objetivo deste estudo in vitro foi avaliar a redução da força de diferentes cadeias elastoméricas após diferentes tempos: inicial, 10 minutos, 1 dia, 28 dias e após escovação mecânica. Vinte segmentos de cadeias elastoméricas ortodônticas foram utilizadas para cada marca comercial. Inicialmente, a cadeia elastomérica de 15 mm de comprimento foi esticada imediatamente até 20 mm na Instron e a força foi medida em (gf). Após, todas as amostras foram adaptadas esticadas em placas retangulares de acrílico na distância de 20 mm, imersas em água deionizada a 37o C por 10 minutos e a força (gf) foi medida novamente. Cinco medidas de força foram feitas nos seguintes intervalos de tempo: inicial, 10 minutos, 1 dia, 28 dias e após a escovação mecânica. Após 28 dias, as placas de acrílico com as amostras foram adaptadas na máquina de escovação (MSCT 3) e as cadeias elastoméricas foram submetidas a escovação mecânica e a medida de força (gf) novamente. Os dados da força (gf) foram submetidos a ANOVA modelo misto e teste post-hoc de Sidak (α = 0,05). Uma redução estatisticamente significativa na força foi encontrada para todos os tipos de cadeia elastomérica ortodôntica após 1 dia, 28 dias e escovação mecânica (p<0,05). As cadeias elastoméricas Morelli e 3M Unitek apresentaram força significativamente superior em relação a Abzil e GAC (p<0,05) após 1 dia, 28 dias e escovação mecânica. Em conclusão, a força distribuída por todas as cadeias elastoméricas decaiu rapidamente com o tempo. As cadeias elastoméricas Morelli e 3M Unitek consistentemente tiveram uma força significativamente maior após a escovação mecânica, enquanto GAC a mais baixa.


Subject(s)
Orthodontic Appliances , Elastomers , Stress, Mechanical , Toothbrushing , Materials Testing , Elasticity
2.
Braz. dent. j ; 32(1): 34-41, Jan.-Feb. 2021. tab, graf
Article in English | LILACS, BBO | ID: biblio-1180717

ABSTRACT

Abstract The objective of this study was to compare the biomechanical behavior of peri-implant bone tissue and prosthetic components in two modalities of treatment for posterior region of the maxilla, using short implants or standard-length implants associated with bone graft in the maxillary sinus. Four 3D models of a crown supported by an implant fixed in the posterior maxilla were constructed. The type of implant: short implant (S) or standard-length implant with the presence of sinus graft (L) and type of crown retention: cemented (C) or screwed (S) were the study factors. The models were divided into SC- cemented crown on a short implant; SS- screwed crown on the short implant; LC- cemented crown on a standard-length implant after bone graft in the maxillary sinus and LS- crown screwed on a standard-length implant after bone graft in the maxillary sinus. An axial occlusal loading of 300 N was applied, divided into five points (60N each) corresponding to occlusal contact. The following analysis criteria were observed: Shear Stress, Maximum and Minimum Main Stress for bone tissue and von Mises Stress for the implant and prosthetic components. The use of standard-length implants reduced the shear stress in the cortical bone by 35.75% and the medullary bone by 51% when compared to short implants. The length of the implant did not affect the stress concentration in the crown, and the cement layer acted by reducing the stresses in the ceramic veneer and framework by 42%. Standard-implants associated with cemented crowns showed better biomechanical behavior.


Resumo O objetivo do estudo foi avaliar o comportamento biomecânico do tecido ósseo peri-implantar e dos componentes protéticos em duas modalidades de tratamento para região posterior da maxila, utilizando implantes curtos ou implantes de comprimento padrão associados a enxerto ósseo em seio maxilar. Foram construídos quatro modelos 3D de uma coroa suportada por um implante osseointegrado na região posterior da maxila. O tipo de implante: implante curto (S) ou implante de comprimento padrão com presença de enxerto sinusal (L) e tipo de retenção da restauração: cimentada (C) ou parafusada (S) foram os fatores de estudo. Foi aplicada uma força oclusal de 300N, dividida em cinco pontos (60 N cada) correspondentes ao contato oclusal de um primeiro molar superior. Foram observados os seguintes critérios de análise: tensão de cisalhamento, tensão principal máxima e mínima para o tecido ósseo e tensão de Von Mises para o implante e componentes protéticos. O uso de implantes de comprimento padrão reduziu a tensão de cisalhamento no osso cortical em 35,75% e no osso medular em 51% quando comparado aos implantes curtos. O comprimento do implante não afetou a concentração de tensão na restauração. A camada de cimento atuou reduzindo as tensões na cerâmica de cobertura e infraestrutura de cerâmica em 42%. Os implantes de tamanho padrão associados às coroas cimentadas apresentaram o melhor comportamento biomecânico.


Subject(s)
Dental Implants , Maxilla/surgery , Stress, Mechanical , Dental Prosthesis Design , Dental Prosthesis, Implant-Supported , Finite Element Analysis , Crowns , Dental Stress Analysis
3.
Article in Chinese | WPRIM | ID: wpr-888213

ABSTRACT

This study aims to overcome the shortcomings such as low efficiency, high cost and difficult to carry out multi-parameter research, which limited the optimization of infusion bag configuration and manufacture technique by experiment method. We put forward a fluid cavity based finite element method, and it could be used to simulate the stress distribution and deformation process of infusion bag under external load. In this paper, numerical models of infusion bag with different sizes was built, and the fluid-solid coupling deformation process was calculated using the fluid cavity method in software ABAQUS subject to the same boundary conditions with the burst test. The peeling strength which was obtained from the peeling adhesion test was used as failure criterion. The calculated resultant force which makes the computed peeling stress reach the peeling strength was compared with experiment data, and the stress distribution was analyzed compared with the rupture process of burst test. The results showed that considering the errors caused by the difference of weak welding and eccentric load, the flow cavity based finite element method can accurately model the stress distribution and deformation process of infusion bag. It could be useful for the optimization of multi chamber infusion bag configuration and manufacture technique, leading to cost reduction and study efficiency improvement.


Subject(s)
Finite Element Analysis , Software , Stress, Mechanical
4.
Acta Physiologica Sinica ; (6): 539-550, 2021.
Article in Chinese | WPRIM | ID: wpr-887689

ABSTRACT

The article aims to study the effect and mechanism of shear stress on eicosanoids produced by the metabolism of polyunsaturated fatty acids in endothelial cells. First, human umbilical vein endothelial cells were treated by control (Static), laminar shear stress (LSS) and oscillatory shear stress (OSS) for 6 h. Then the endothelial cells were incubated with fresh M199 medium for 3 h, and the cell culture medium was collected. Ultra-performance liquid chromatography-mass spectrometer was used to detect the level of eicosanoid metabolites secreted by endothelial cells. The results showed that under different shear stress, the level of eicosanoid metabolites were changed significantly. We found 10 metabolites were significantly up-regulated by OSS compared with those in LSS group, including PGD2, PGE2, PGF2α and PGJ2 produced by cyclooxygenase; 11-HETE, 15-HETE, 13-HDoHE produced by lipoxygenase or spontaneous oxidation; 12,13-EpOME, 9,10-EpOME, 9,10-DiHOME produced by cytochrome P450 oxidase and soluble epoxide hydrolase. The transcription levels of these up-regulated eicosanoids metabolic enzyme-related genes were also increased in vitro and in vivo. These results indicate that OSS may promote the increase of metabolites by up-regulating the transcription level of metabolic enzyme-related genes, which playing a key role in the development of atherosclerosis. This study reveals the effect of shear stress on eicosanoid metabolism in endothelial cells, which provides a novel supplement to the systems biology approach to study systemic hemodynamics.


Subject(s)
Cells, Cultured , Eicosanoids , Human Umbilical Vein Endothelial Cells , Humans , Metabolomics , Stress, Mechanical
5.
Journal of Biomedical Engineering ; (6): 1097-1102, 2021.
Article in Chinese | WPRIM | ID: wpr-921850

ABSTRACT

Atherosclerotic plaque rupture is the main cause of many cardiovascular diseases, and biomechanical factors play an important role in the process of plaque rupture. In the study of plaque biomechanics, there are relatively few studies based on fatigue fracture failure theory, and most of them mainly focus on the whole fatigue propagation process from crack initiation to plaque rupture, while there are few studies on the influence of crack on plaque rupture at a certain time in the process of fatigue propagation. In this paper, a two-dimensional plaque model with crack was established. Based on the theory of fracture mechanics and combined with the finite element numerical simulation method, the stress intensity factor (SIF) and related influencing factors at the crack tip in the plaque were studied. The SIF was used to measure the influence of crack on plaque rupture. The results show that the existence of crack can lead to local stress concentration, which increases the risk of plaque rupture. The SIF at the crack tip in the plaque was positively correlated with blood pressure, but negatively correlated with fibrous cap thickness and lipid pool stiffness. The effect of the thickness and angle of lipid pool on the SIF at the crack tip in the plaque was less than 4%, which could be ignored. This study provides a theoretical basis for the risk assessment of plaque rupture with cracks.


Subject(s)
Biomechanical Phenomena , Computer Simulation , Humans , Plaque, Atherosclerotic , Stress, Mechanical
6.
Article in Chinese | WPRIM | ID: wpr-879278

ABSTRACT

Lower extremity movement is a complex and large range of limb movement. Arterial stents implanted in lower extremity are prone to complex mechanical deformation, so the stent is required to have high comprehensive mechanical properties. In order to evaluate the mechanical property of different stents, in this paper, finite element method was used to simulate and compare the mechanical properties of six nitinol stents (Absolute Pro, Complete SE, Lifestent, Protégé EverFlex, Pulsar-35 and New) under different deformation modes, such as radial compression, axial compression/tension, bending and torsion, and the radial support performance of the stents was verified by experiments. The results showed that the comprehensive performance of New stent was better than other stents. Among which the radial support performance was higher than Absolute Pro and Pulsar-35 stent, the axial support performance was better than Complete SE, Lifestent and Protégé EverFlex stent, the flexibility was superior to Protégé Everflex stent, and the torsion performance was better than Complete SE, Lifestent and Protégé Everflex stent. The TTR2 type radial support force tester was used to test the radial support performance of 6 types, and the finite element analysis results were verified. The mechanical properties of the stent are closely related to the structural size. The result provides a reference for choosing a suitable stent according to the needs of the diseased location in clinical applications.


Subject(s)
Alloys , Femoral Artery , Finite Element Analysis , Lower Extremity , Mechanical Phenomena , Prosthesis Design , Stents , Stress, Mechanical
7.
Article in Chinese | WPRIM | ID: wpr-879277

ABSTRACT

In the study of oral orthodontics, the dental tissue models play an important role in finite element analysis results. Currently, the commonly used alveolar bone models mainly have two kinds: the uniform and the non-uniform models. The material of the uniform model was defined with the whole alveolar bone, and each mesh element has a uniform mechanical property. While the material of the elements in non-uniform model was differently determined by the Hounsfield unit (HU) value of computed tomography (CT) images where the element was located. To investigate the effects of different alveolar bone models on the biomechanical responses of periodontal ligament (PDL), a clinical patient was chosen as the research object, his mandibular canine, PDL and two kinds of alveolar bone models were constructed, and intrusive force of 1 N and moment of 2 Nmm were exerted on the canine along its root direction, respectively, which were used to analyze the hydrostatic stress and the maximal logarithmic principal strain of PDL under different loads. Research results indicated that the mechanical responses of PDL had been affected by alveolar bone models, no matter the canine translation or rotation. Compared to the uniform model, if the alveolar bone was defined as the non-uniform model, the maximal stress and strain of PDL were decreased by 13.13% and 35.57%, respectively, when the canine translation along its root direction; while the maximal stress and strain of PDL were decreased by 19.55% and 35.64%, respectively, when the canine rotation along its root direction. The uniform alveolar bone model will induce orthodontists to choose a smaller orthodontic force. The non-uniform alveolar bone model can better reflect the differences of bone characteristics in the real alveolar bone, and more conducive to obtain accurate analysis results.


Subject(s)
Biomechanical Phenomena , Computer Simulation , Finite Element Analysis , Humans , Models, Biological , Periodontal Ligament , Stress, Mechanical , Tooth Movement Techniques
8.
Dental press j. orthod. (Impr.) ; 26(2): e211945, 2021. tab, graf
Article in English | LILACS, BBO | ID: biblio-1249705

ABSTRACT

ABSTRACT Objective: This paper aims to verify the thermodynamic, mechanical and chemical properties of CuNiTi 35ºC commercial wires. Methods: Forty pre-contoured copper-nickel-titanium thermodynamic 0.017 x 0.025-in archwires with an Af temperature of 35°C were used. Eight wires from five different manufacturers (American Orthodontics® [G1], Eurodonto® [G2], Morelli® [G3], Ormco® [G4] and Orthometric® [G5]) underwent cross-sectional dimension measurements, tensile tests, SEM-EDS and differential scanning calorimetry (DSC) tests. Parametric tests (One-way ANOVA and Tukey post-test) were used, with a significance level of 5%, and Pearson's correlation coefficient test was performed between the Af and chemical elements of the wires. All sample tests and statistical analyses were double-blinded. Results: All wires presented standard dimensions (0.017 x 0.025-in) and superelastic behavior, with mean plateau forces of: G1 = 36.49N; G2 = 27.34N; G3 = 19.24 N; G4 = 37.54 N; and G5 = 17.87N. The Af means were: G1 = 29.40°C, G2 = 29.13°C and G3 = 31.43°C, with p>0.05 relative to each other. G4 (32.77°C) and G5 (35.17°C) presented statistically significant differences between each other and among the other groups. All samples presented Ni, Ti, Cu and Al in different concentrations. Conclusions: The chemical concentration of the elements that compose the alloy significantly influenced the thermodynamic and mechanical properties.


RESUMO Objetivo: O presente artigo teve como objetivo verificar as propriedades termodinâmicas, mecânicas e químicas de fios CuNiTi 35°C comerciais. Métodos: Foram utilizados 40 arcos termodinâmicos pré-contornados de cobre-níquel-titânio de 0,017" x 0,025" e temperatura Af de 35°C. Oito fios de cinco fabricantes diferentes (American Orthodontics® [G1], Eurodonto® [G2], Morelli® [G3], Ormco® [G4] e Orthometric® [G5]) foram submetidos a medições de suas secções transversais, testes de tração, MEV-EDS e calorimetria diferencial (DSC). Foram utilizados testes paramétricos (One-way ANOVA e pós-teste de Tukey), com nível de significância de 5%, e foi realizado o teste do coeficiente de correlação de Pearson entre a temperatura Af e os elementos químicos dos fios. Todos os testes das amostras e análises estatísticas foram duplo-cegos. Resultados: Todos os fios apresentavam dimensões padronizadas (0,017" x 0,025") e comportamento superelástico, com forças médias de platô de G1 = 36,49 N; G2 = 27,34 N; G3 = 19,24 N; G4 = 37,54 N; e G5 = 17,87 N. As médias de Af foram: G1 = 29,40°C, G2 = 29,13°C e G3 = 31,43°C, com p> 0,05 entre si. G4 (32,77°C) e G5 (35,17°C) apresentaram diferenças estatisticamente significativas entre si e entre os demais grupos. Todas as amostras apresentaram Ni, Ti, Cu e Al em diferentes concentrações. Conclusões: A concentração química dos elementos que compõem a liga influenciou significativamente as propriedades termodinâmicas e mecânicas.


Subject(s)
Orthodontic Wires , Dental Alloys , Stress, Mechanical , Titanium , Materials Testing , Cross-Sectional Studies , Elasticity
9.
Braz. oral res. (Online) ; 35: e021, 2021. tab, graf
Article in English | LILACS, BBO | ID: biblio-1153624

ABSTRACT

Abstrac The aim of the present study was to evaluate the cyclic fatigue, torsional resistance and surface roughness of Reciproc R25 instruments in four different situations, namely as new instruments and as instruments tested after clinical preparation of one, two or three maxillary molars with four root canals. The total time required to perform each root canal preparation was recorded. Cyclic fatigue resistance was determined by the time to fracture using a customized testing device (n = 10 per group). The torsional test evaluated the torque and angle of rotation to failure according to ISO 3630-1 (n = 10 per group). The roughness of the working parts of new and used instruments was evaluated with a profilometer (n = 5 per group). Statistical analysis was performed using one-way ANOVA and Tukey's test. The level of significance was set at 5%. No fractures or deformations were observed after clinical use. Higher preparation time was needed during the third use of the instruments for all root canals (p < 0.05). There were no significant differences among the groups in regard to either cyclic fatigue or torsional resistance (p > 0.05). Regarding the roughness measurements, groove depth was higher on new and one- versus two- or three-maxillary-molar-prepared instruments (p < 0.05). It can be concluded that the clinical use of Reciproc instruments increased preparation time and decreased surface roughness. However, clinical use did not affect the cyclic fatigue or torsional resistance of the Reciproc instruments.


Subject(s)
Titanium , Root Canal Preparation , Stress, Mechanical , Materials Testing , Torque , Dental Instruments , Equipment Design
10.
São José dos Campos; s.n; 2021. 99 p. ilus, graf, tab.
Thesis in Portuguese | LILACS, BBO | ID: biblio-1362094

ABSTRACT

Este estudo avaliou o efeito de 3 desenhos de preparos dentários para restaurações parciais indiretas de cobertura total na veracidade e precisão de modelos digitais obtidos por 3 escâneres intraorais; e na tensão de contração de polimerização residual por meio de análise de elementos finitos. Foram considerados os seguintes preparos: contendo redução de istmo (IST); sem redução de istmo (wIST) e preparo não retentivo (nRET). Para avaliação da veracidade e precisão, 10 varreduras foram realizadas em modelos referência de resina epóxi de contendo os dentes 45, 47 e com preparo no 46. Os modelos de referência digital foram obtidos usando um escâner industrial. Três escâneres intraorais foram comparados (n=10): Element 2 (ELE); Trios 3 (TRI); Primescan (PRI). A veracidade (µm) e a precisão (µm) foram analisadas em um software de sobreposição tridimensional. Os dados foram analisados utilizando os testes de Kruskal-Wallis e Dunn (α = 0,05). Para avaliar a tensão de contração, os preparos foram modelados em um dente 46 contendo: esmalte, dentina, cimento, restauração de cerâmica, polpa, ligamento periodontal, osso cortical e esponjoso. As interfaces foram consideradas coladas e os volumes considerados homogêneos, lineares e isotrópicos. A contração do cimento foi simulada e critério de Tensão Máxima Principal foi adotado para análise dos resultados. O preparo não retentivo obteve maior veracidade (3,8 µm) e precisão (2,7 µm) em comparação com os demais (veracidade = 6-7 µm, precisão = 4-5 µm). A veracidade foi menor no grupo ELE × IST (16), seguido por ELE × wIST (13 µm) e PRI × IST (7,8 µm). Não foi encontrada diferença entre os escâneres PRI e TRI (6 µm), com desempenho inferior para ELE (13 µm). As discrepâncias positivas foram maiores na proximal em IST e wIST. Os picos de tensão (MPa) de contração seguiram a seguinte sequência: restauração=IST (13,4) > wIST (9,3) > nRET (9); cimento=IST (16,9) > wIST (12,6) > nRET (10-7,5); dente=IST (10,7) > wIST (10,5) > (9). Conclui-se que o preparo nRET foi vantajoso para a redução da tensão de contração e para a obtenção de modelos com maior veracidade e precisão.


This study evaluated the effect of 3 preparations designs for full-coverage onlay on the accuracy of digital models obtained by intraoral scanners; and in the polymerization residual shrinkage stress by means of finite element analysis. The following preparations were evaluated: with isthmus preparation (IST); without isthmus preparation (sIST) and non-retentive preparation (nRET). For the evaluation of accuracy, 10 digital impressions were performed in a reference epoxy resin model from a lower hemiarch (teeth 45, 46 and 47) with a preparation on the teeth 46. The digital reference models were obtained using an industrial scanner. Three intraoral scanners were compared (n=10): Element 2 (ELE); Trios 3 (TRI); Primescan (PRI). Trueness (µm) and precision (µm) were analyzed using a three-dimensional superimposition software. Data were analyzed using Kruskal-Wallis and Dunn tests (α = 0.05). To assess the shrinkage stress, the preparations were modeled on a tooth #46 containing: enamel, dentin, cement, ceramic restoration, pulp, periodontal ligament, cortical and cancellous bone. The interfaces were considered bonded and the volumes as homogeneous, linear and isotropic. The cement shrinkage was simulated, and the Maximum Principal Stress criterion was adopted to analyze the results. The non-retentive preparation had greater trueness (3.8 µm) and precision (2.7 µm) compared to the others (trueness = 6-7 µm, precision = 4-5 µm). The trueness was lower in the ELE × IST (16), followed by ELE × wIST (13 µm) and PRI × IST (7.8 µm). No difference was found between PRI and TRI scanners (6 µm), with lower performance for ELE (13 µm). Positive discrepancies were greater in the proximal in IST and wIST. The stress (MPa) of followed the sequence: restoration=IST (13.4) > wIST (9.3) > nRET (9); cement=IST (16.9) > wIST (12.6) > nRET (10-7.5); tooth=IST (10.7) > wIST (10.5) > (9). It can be concluded that the nRET preparation was advantageous for reducing the contraction stress and for obtaining models with greater accuracy and precision.


Subject(s)
Stress, Mechanical , Finite Element Analysis , Data Accuracy , Inlays
11.
Dental press j. orthod. (Impr.) ; 25(6): 59-68, Nov.-Dec. 2020. tab, graf
Article in English | LILACS, BBO | ID: biblio-1154058

ABSTRACT

ABSTRACT Objectives: Assess the stability of three different mini-implants, based on thread shape factor (TSF), and evaluate stresses at the mini-implant site and surrounding cortical bone on application of retraction force, at two different insertion angles. Methods: Mini-implants of three different diameters (M1 - Orthoimplant, 1.8mm), (M2 - Tomas, 1.6mm) and (M3 - Vector TAS, 1.4mm) and length of 8mm were used. Using scanning electronic microscopy, the mean thread depth, pitch and relationship between the two (TSF) were calculated. The mini-implants were loaded into a synthetic bone block and the pull-out strength was tested. One way ANOVA and Tukey post-hoc tests were used to compare the pull-out strength of mini-implants. P values < 0.05 were considered statistically significant. Finite element models (FEM) were constructed with insertion angulation at 90° and 60°, with retraction force of 150 g. The results were analyzed using ANSYS software. Results: Statistically significant difference was found among all the three mini-implants for thread depth and pitch (< 0.001). Statistically significant higher pull-out force value was seen for Orthoimplant. The stress distribution level in mini-implant and surrounding bone was observed to be smaller for Orthoimplant. Conclusion: Orthoimplant mini-implants have more favorable geometric characteristics among the three types, and less stress with 90°angulation.


RESUMO Objetivos: Avaliar a estabilidade de três diferentes tipos de mini-implantes, com base no fator formato da rosca (thread shape factor, TSF), e avaliar a tensão no local de inserção e no osso cortical ao redor dos mini-implantes inseridos com dois ângulos diferentes, durante a aplicação de força para retração. Métodos: Foram usados três diferentes diâmetros de mini-implantes, sendo eles 1,8 mm (M1, ORTHO Implant), 1,6 mm (M2, Tomas) e 1,4 mm (M3, Vector TAS), todos com comprimento de 8 mm. Por meio da microscopia eletrônica de varredura, foram calculados a profundidade da rosca, o passo da rosca (distância entre os filetes da rosca) e a relação entre os dois (TSF). Para realização do teste de tração (pull-out), os mini-implantes foram inseridos em um bloco de osso sintético. Os testes ANOVA de uma via e post-hoc de Tukey foram usados para comparar as forças de resistência à tração dos mini-implantes, considerando-se estatisticamente significativos valores de p< 0,05. Modelos de elementos finitos (MEF) foram gerados com ângulos de inserção dos mini-implantes a 90° e 60°, com força de retração em 150g. Os resultados foram analisados usando-se o software ANSYS. Resultados: Diferenças estatisticamente significativas foram encontradas entre os três mini-implantes quanto à profundidade da rosca e o passo da rosca (p< 0,001). O ORTHO Implant apresentou a maior força de resistência à tração, com significância estatística. O nível de distribuição das tensões no mini-implante e no osso circundante também foi menor para o ORTHO Implant. Resultados: Entre os diferentes tipos de mini-implantes analisados, o ORTHO Implant apresentou as características geométricas mais favoráveis e a menor tensão com o ângulo de inserção de 90°.


Subject(s)
Dental Implants , Dental Stress Analysis , Stress, Mechanical , Software , Finite Element Analysis
12.
Braz. dent. j ; 31(5): 540-547, Sept.-Oct. 2020. graf
Article in English | LILACS, BBO | ID: biblio-1132326

ABSTRACT

Abstract The aim of this study was to analyze the influence of orthodontic bracket type (metallic or ceramic) and mouthguard on biomechanical response during impact. Two-dimensional plane-strain models of a patient with increased positive overjet of the maxillary central incisor was created based on a CT scan, simulating the periodontal ligament, bone support, gingival tissue, orthodontic brackets (metallic or ceramic) and mouthguard. A nonlinear dynamic impact finite element analysis was performed in which a steel object hit the model at 1 m/s. Stress distributions (Von Mises and Modified Von Mises) and strain were evaluated. Stress distributions were affected by the bracket presence and type. Models with metallic and ceramic bracket had higher stresses over a larger buccal enamel impact area. Models with ceramic brackets generated higher stresses than the metallic brackets. Mouthguards reduced the stress and strain values regardless of bracket type. Mouthguard shock absorption were 88.37% and 89.27% for the metallic and ceramic bracket, respectively. Orthodontic bracket presence and type influenced the stress and strain generated during an impact. Ceramic brackets generated higher stresses than metallic brackets. Mouthguards substantially reduced impact stress and strain peaks, regardless of bracket type.


Resumo O objetivo deste estudo foi analisar a influência da presença e tipo de bráquete ortodôntico (metálico ou cerâmico), e a presença de protetor bucal na resposta biomecânica durante impacto. Modelos bidimensionais em estado plano de deformação de paciente com incisivo central superior com overjet positivo acentuado foram criados baseados em tomografia computadorizada, simulando ligamento periodontal, suporte ósseo, tecido gengival, bráquetes ortodônticos (metálico e cerâmico) e o protetor bucal. Análise de elementos finitos não-linear de impacto foi realizada na qual uma esfera de aço atingiu o modelo a 1m/s. A distribuição de tensões (Von Mises e Von Mises modificado) e a deformação foram avaliadas. As distribuições de tensões foram afetadas pela presença e tipo de bráquete. Modelos com bráquete metálico e cerâmico produziram maiores valores de tensões sobre maior área do esmalte vestibular. Modelos com bráquetes cerâmicos geraram maiores tensões do que metálicos. O protetor bucal reduziu as tensões e deformações geradas independentemente do tipo de bráquete. A capacidade de absorção de choques foi de 88.37 e 89.27% para os bráquetes metálicos e cerâmicos, respectivamente. A presença e o tipo de bráquete influenciou a distribuição de tensões e deformações durante o impacto. Bráquetes cerâmicos geraram maiores valores de tensão do que metálicos. Protetor bucal reduziu significativamente os picos de tensão e deformação.


Subject(s)
Humans , Orthodontic Brackets , Mouth Protectors , Stress, Mechanical , Materials Testing , Ceramics , Orthodontic Appliance Design , Finite Element Analysis , Dental Stress Analysis , Incisor
13.
Saude e pesqui. (Impr.) ; 13(1): 53-61, jan/mar 2020. ilus
Article in Portuguese | LILACS | ID: biblio-1052901

ABSTRACT

Estresse é a resposta aos diferentes estímulos que o organismo sofre em busca de adaptação à homeostasia. Devido à sua alta incidência, diversos modelos experimentais estão sendo desenvolvidos para a melhor compreensão de sua inter-relação com outros órgãos. Neste contexto, o objetivo deste estudo foi avaliar os efeitos em longo prazo do estresse físico e psicológico juvenil agudo sobre as glândulas suprarrenais de ratos, no que se refere aos aspectos morfológicos, pois tais glândulas apresentam relação direta com situações de estresse. Para tanto, as glândulas suprarrenais destes animais foram processadas e análises morfológicas da medula e do córtex foram realizadas por meio de morfometria e quantificação por planimetria. Os resultados obtidos demonstraram que o estresse tanto físico quanto psicológico não provocaram alterações significativas em relação à área de superfície e espessura das suprarrenais, indicando adaptação dos animais aos fatores estressantes aqui estudados.


Stress is a response to different stimuli experienced by the organism for its adaption to homeostasis. Due to its high occurrence, several experimental models are being developed to understand better the interrelationships between these organs. Current paper evaluates long-term effects of juvenile physical and psychological stress on the suprarenal glands of rats with regard to morphological aspects. In fact, these glands have a direct relationship with stress conditions. Rats´ suprarenal glands were processed and their medulla and cortex were morphologically investigated through planimetry. Results show that physical and psychological stress failed to cause significant changes on the surface area and thickness of the glands. This fact showed adaptation of animals to the type of stress under analysis.


Subject(s)
Animals , Mice , Stress, Mechanical , Stress, Psychological , Adrenal Glands , Cell Nucleus Shape
14.
Int. j. odontostomatol. (Print) ; 14(1): 60-66, mar. 2020. tab, graf
Article in English | LILACS | ID: biblio-1056502

ABSTRACT

ABSTRACT: The objective of the study was to evaluate marginal adaptation of Class II mesial-occlusal-distal (MOD) restorations before and after thermo-mechanical loading and volumetric shrinkage of the bulk-fill vs conventional composite resin. For marginal adaptation assessment, 24 Class II MOD cavities with cervical margins extending 1.0 mm below (distal) and 1.0 mm beyond (mesial) the cement-enamel junction were prepared in extracted human molars. The teeth were filled as follows: Group A - bulk-fill with SureFil SDR flow (first increment, 4 mm; second increment, 2 mm); Group B - bulk-fill with SureFil SDR flow as a base (first increment, 4 mm) and covered with the conventional nanohybrid composite Esthet-X HD (second increment, 2 mm); and Group C - incrementally filled with Esthet-X HD. Marginal adaptation was evaluated by scanning electron microscopy before and after thermomechanical loading (240,000 loading cycles and simultaneous 600 thermal cycles). To evaluate volumetric polymerization shrinkage, a semi-spherical mold was filled with the tested composites and placed in an AccuVol device after light curing. Both before and after loading, marginal adaptation in cervical dentin was superior (p < 0.05) for Groups A and B compared with Group C. In cervical enamel, Group B showed better marginal adaptation than Group C, and Group A presented intermediary results, between Groups B and C. Furthermore, bulk-fill flow resulted in greater shrinkage than Esthet-X HD. A significant improvement of marginal adaptation was observed when bulkfill flow was used instead of conventional composite resin both before and after thermomechanical loading. However, the bulk-fill flow presented higher volumetric polymerization shrinkage than the conventional composite.


RESUMEN: El objetivo de este trabajo consistió en evaluar la adaptación marginal de las restauraciones mesiales-oclusales-distales (MOD) de Clase II antes y después de la carga termo-mecánica y la contracción volumétrica de la carga compuesta de resina "bulk-fill" en comparación con resina convencional. Para la evaluación de adaptación, se prepararon 24 cavidades MOD de Clase II en molares humanos extraídos, los que se restauraron de la siguiente manera: Grupo A: restaurado con resina fluida Bulk-Fill SureFilSDR (primer incremento, 4 mm; segundo incremento, 2 mm); Grupo B: restaurado con resina fluida Bulk-Fill SureFil SDR (primer incremento, 4 mm) y cubierto con resina compuesta nanohíbrida Esthet-X HD (segundo incremento, 2 mm); y Grupo C - rellenado incrementalmente con Esthet-X HD. La adaptación marginal se evaluó mediante microscopía electrónica de barrido antes y después de la carga termomecánica (240.000 ciclos de carga y 600 ciclos térmicos simultáneos). Para evaluar la contracción volumétrica de la polimerización, se llenó un molde semiesférico con los compuestos probados y se colocó en un dispositivo AccuVol después del fotopolimerización. Tanto antes como después de la carga, la adaptación marginal en la dentina cervical fue superior (p <0,05) para los grupos A y B en comparación con el grupo C. En el esmalte cervical, el grupo B mostró una mejor adaptación marginal que el grupo C, y el grupo A presentó resultados intermedios, entre Grupos B y C. Se observó una mejora significativa de la adaptación marginal al utilizar la resina fluida Bulk-Fill en lugar de resina compuesta convencional tanto antes como después de la carga termomecánica. Sin embargo, la resina fluida 'Bulk-Fill' presentó una mayor contracción volumétrica de polimerización que el compuesto convencional.


Subject(s)
Humans , Dental Marginal Adaptation , Composite Resins , Dental Cavity Preparation/instrumentation , Dental Restoration, Permanent/methods , Malocclusion, Angle Class II , Stress, Mechanical , Statistical Analysis , Ethics Committees , Dental Restoration Wear , Dental Cavity Preparation/standards , Polymerization
15.
Article in Chinese | WPRIM | ID: wpr-828267

ABSTRACT

OBJECTIVE@#To construct a dynamic knee joint finite element model based on CT image data and verify the validity of the model. To provide a simulation model and basic data for biomechanical research of the knee joint by further finite element analysis.@*METHODS@#The CT data of a healthy male knee joint was selected. With the help of Mimics 19.0 and Hypermesh 12.0 software, a high simulation finite element model of knee joint was established following steps, including geometric reconstruction, reverse engineering, meshing and material characterization. The dynamic knee flexion model was generated by determining the boundary conditions and torque loading, and the validity of themodel was confirmed. The biomechanical changes of the tibiofemoral and patellofemoral joints under different knee flexion angles were analyzed by applying the loads (500 N) to the finite element model during knee flexion.@*RESULTS@#A finite element model of knee joint was established based on CT images and anatomical characteristics. The model included three-dimensional elements such as bone, ligament, cartilage, meniscus and patellar retinaculum. The different finite element models of knee flexion states were produced by applying different torques after establishing boundary conditions. According to equivalent conditions (knee flexion 30 degrees, quadriceps tendon under 200 N stretch), the peak stress value of patella was 2.209 MPa and the average Mises stress was 1.132 MPa; the peak stress value of femoral trochlear was 1.405 MPa and the average Mises stress was 0.936 MPa. The validity of the model was proved by the difference between the model and previous studies of 1% to 13.5%. Dynamic model loading showed that the Mises stressof tibiofemoral joint decreased with the increase of knee flexion angle, while the Mises stress of patellofemoral joint was positively correlated with knee flexion angle. The Mises stress of cartilage stress planes at different knee flexion angles was significantly different(<0.05).@*CONCLUSION@#The finite element model established in this study is more comprehensive and can effectively simulate the biomechanical characteristics of dynamic knee joint, which provides support for further simulation mechanics researches of the knee joint.


Subject(s)
Biomechanical Phenomena , Finite Element Analysis , Humans , Knee Joint , Diagnostic Imaging , Male , Patella , Stress, Mechanical , Tomography, X-Ray Computed
16.
Article in Chinese | WPRIM | ID: wpr-828251

ABSTRACT

OBJECTIVE@#In order to select the proper size of prosthesis ball head, the biomechanical changes of hip joint using different diameter prosthesis ball head was studied by three-dimensional finite element analysis.@*METHODS@#The thin-layer CT data and related parameters of artificial femoral head prosthesis were used to establish the finite element model of hip joint after artificial femoral head replacement with different ball diameter of prosthesis(M0:preoperative model;M1:ball head diameter=original femoral head diameter;M2:ball head diameter=original femoral head diameter+1 mm;M3:Ball head diameter= Original femoral head diameter -1 mm;M4:ball head diameter =original femoral head diameter -2 mm). Loading the joint forces and related muscle loads were loaded, and the stress distribution and change of bone and cartilage around acetabulum were analyzed by simulating the standing state of one foot when walking slowly.@*RESULTS@#(1) In M1 to M4, the stress concentration in pelvis was different. The peak value of Von Mises stress in the pelvis of M3 was 44.8 MPa, which was the closest to that before operation, with an increment of 13.4%. The displacement of the pelvis of M3 was the smallest in the four groups after operation, with an increment of 1.40 mm. The next was M1, with a peak value of 47.3 MPa, with an increment of 19.7%, and a pelvic displacement of 1.59 mm. (2) In acetabulum area, the peak value of Von Mises stress in M3 was 23.3 MPa, which was the closest to that before operation, with an increment of about 6.3%, followed by M1, with a peak value of 24.0 MPa and an increment of about 8.1%. (3) On the acetabulum cartilage, the stress distribution of M1 and M3 was similar to that before operation, and the peak value of Von Mises stress of M3 was 18.5 MPa, which was the closest to that before operation, followed by M1, which was 22.5 MPa. (4) M1 to M4 showed different degree of stress concentration in the outer upper quadrant of the artificial femoral head, but showed stress shielding under it;among them, the von Mises stress distribution of M3 was more uniform than that of other models, and its peak value (70.8 MPa) was the lowest in each group, followed by M1 (80.7 MPa).@*CONCLUSION@#When femoral head replacement is performed, it is suggested that the prosthesis ball head with the diameter less than 1 mm and the prosthesis ball head with the same diameter as the original femoral head should be used first, so as to obtain the closest natural mechanical characteristics of the hip joint before the replacement and reduce the risk of complications caused by size differences.


Subject(s)
Femur Head , Finite Element Analysis , Hip Joint , Hip Prosthesis , Stress, Mechanical
17.
Article in Chinese | WPRIM | ID: wpr-828209

ABSTRACT

OBJECTIVE@#To establish a 3D finite element model of normal knee joint involved its meniscus, which can be used to simulate the anatomical morphology and characteristics of human knee joint, to verify the validity of the model by preliminary FEA mechanical analysis, and explain partially biomechanical mechanisms of meniscus.@*METHODS@#CT and MRI data were harvested by scanning the knee joint of a healthy male volunteer, and then these data were imported into Mimics 10.01 software and Geomagic Studio software to constructed the 3D models of tissue structures of knee joint. These models were combined to constructed the 3D model of intact knee joint and meshed in ANSA software. Therefore the finite element model of intact knee joint was established. Finally, after the definitionof its material behavior, boundary conditions and loading. The finite element model of knee joint was analyzed and verified using ANSYS software. Meanwhile The biomechanical properties of meniscus were analyzed.@*RESULTS@#The complete knee finite element model composed of bone, meniscus, articular cartilage, and major ligaments was established. It could effectively simulate the anatomical morphology and characteristics of knee joint and its meniscus. The contact area of medial meniscus was 771.05 mm, while the contact area of lateral meniscus was 634.31 mm, and the ratio was 1.216. The stress distribution was uniform, but the stress of the medial meniscus was higher than that of the lateral meniscus, and the peak stress located in the posterior horn of the medial meniscus and the anterior horn of the lateral meniscus, respectively, and the peak stress value was 4.11 MPa. The maximum displacement of the meniscus was located in body, and the displacement of the medial meniscus was more remarkable than that of the lateral meniscus, and the maximum displacement value is 0.33 mm. The obtained finite element analysis results corresponded to that reported in the literature, which mean the model's reliability.@*CONCLUSION@#The established finite element model of knee joint are proved to be have validity, and is a useful model for finite element analysis of meniscus tear and menisectomy. The results of finite element analysis can explain partially biomechanical mechanisms of meniscus which can provide theoretical guidance for clinical treatment of meniscus injury.


Subject(s)
Biomechanical Phenomena , Finite Element Analysis , Humans , Knee Joint , Male , Menisci, Tibial , Meniscus , Reproducibility of Results , Stress, Mechanical
18.
Article in Chinese | WPRIM | ID: wpr-828162

ABSTRACT

In order to evaluate the safety performance of self-expandable NiTi alloy stents systematically, the dynamic safety factor drawn up by International Organization for Standardization, was used to quantitatively reflect the safety performance of stents. Based on the constitutive model of super-elastic memory alloy material in Abaqus and uniaxial tensile test data of NiTi alloy tube, finite element method and experiments on accelerated fatigue life were carried out to simulate the self-expansion process and the shape change process under the action of high and low blood pressure for three -type stents of 8×30 mm, 10×30 mm, 12×30 mm. By analyzing the changes of stress and strain of self-expanding NiTi alloy stent, the maximum stress and strain, stress concentration position, fatigue strength and possible failure modes were studied, thus the dynamic safety factor of stent was calculated. The results showed that the maximum stress and plastic strain of the stent increased with the increase of grip pressure, but the maximum stress and strain distribution area of the stent had no significant change, which were all concentrated in the inner arc between the support and the connector. The dynamic safety factors of the three stents were 1.31, 1.23 and 1.14, respectively, which indicates that the three stents have better safety and reliability, and can meet the fatigue life requirements of more than 10 years, and safety performance of the three stents decreases with the increase of stent's original diameter.


Subject(s)
Alloys , Finite Element Analysis , Nickel , Reproducibility of Results , Self Expandable Metallic Stents , Stress, Mechanical , Titanium
19.
Clinics ; 75: e1123, 2020. tab, graf
Article in English | LILACS | ID: biblio-1101082

ABSTRACT

OBJECTIVE: The objective of this study was to compare two postero-lateral bundle (PLB) tibial fixation techniques for the reconstruction of the anterior cruciate ligament with double bundle: a technique without the use of an interference screw, preserving the native tibial insertion of the tendons of the gracilis and semitendineous muscles, and a technique with the use of an interference screw and without preserving the insertion of the tendons. METHODS: A comparative study was conducted in cadavers with a universal mechanical test machine. In total, 23 cadaver knees were randomized for tibial fixation of the PLB using the two techniques: Maintaining the tibial insertion of the tendons during reconstruction, without the use of an interference screw (group A, 11 cases); and fixating the graft with an interference screw, without maintaining the insertion of the tendons (group B, 12 cases). A continuous traction was performed (20 mm/min) in the same direction as the produced tunnel, and force (N), elongation (mm), rigidity (N/mm), and tension (N/mm2) were objectively determined in each group. RESULTS: Group A exhibited a maximum force (MF) of 315.4±124.7 N; maximum tension of 13.57±3.65 N/mm2; maximum elongation of 19.73±4.76 mm; force at the limit of proportionality (FLP) of 240.6±144.0 N; and an elongation at the limit of proportionality of 14.37±6.58 mm. Group B exhibited a MF of 195.7±71.8 N; maximum tension of 8.8±3.81 N/mm2; maximum elongation of 15.3±10.73 mm; FLP of 150.1±68.7 N; and an elongation at the limit of proportionality of 6.86±2.42 mm. When comparing the two groups, significant differences were observed in the variables of maximum force (p=0.016), maximum tension (p=0.019), maximum elongation (p=0.007), and elongation at the limit of proportionality (p=0.003). CONCLUSION: The use of the native insertion of the semitendineous and gracilis tendons, without an additional fixation device, presented mechanical superiority over their fixation with interference screws.


Subject(s)
Humans , Bone Screws , Anterior Cruciate Ligament/surgery , Muscle, Skeletal/transplantation , Reconstructive Surgical Procedures/instrumentation , Hamstring Tendons/surgery , Anterior Cruciate Ligament Injuries , Stress, Mechanical , Tibia/surgery , Biomechanical Phenomena , Reconstructive Surgical Procedures/methods
20.
Article in Chinese | WPRIM | ID: wpr-828885

ABSTRACT

OBJECTIVE@#To analyze the biomechanics of cystic lesions in the mandibular body in a three-dimensional (3D) finite element model.@*METHODS@#A 3D finite element model of cystic lesion of the mandibular body was constructed based on the CT images of the mandible of a healthy adult female volunteer with normal occlusion. The size of the cyst and the residual bone wall were analyzed when the lesion area approached the stress peak under certain constraints and loading conditions.@*RESULTS@#When the size of the cyst reached 37.63 mm×11.32 mm×21.45 mm, the maximal von Mises stress in the lesion area reached 77.295 MPa, close to the yield strength of the mandible with a risk of pathological fracture. At this point, the remaining bone thickness of the buccal and lingual sides and the lower margin of the mandible in the lesion area was 1.52 mm, 0.76 mm and 1.04 mm, respectively.@*CONCLUSIONS@#Residual bone mass is an important factor to affect the risk of pathological fracture after curettage of cystic lesions. A thickness as low as 1 mm of the residual bone cortex in the cystic lesion area of the mandibular body can be used as the threshold for a clinical decision on one-stage windowing decompression combined with two- stage curettage.


Subject(s)
Adult , Biomechanical Phenomena , Female , Finite Element Analysis , Humans , Imaging, Three-Dimensional , Mandible , Stress, Mechanical
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