Comportamiento Mecánico de un Premolar Humano Sano Sometido a Fuerzas Funcionales y Disfuncionales en un MEF / Mechanical Behavior of a Healthy Human Premolar Subjected to Functional and Dysfunctional Forces in a FEM

El propósito de este estudio fue analizar el comportamiento mecánico de la estructura dental sana de un primer premolar inferior humano sometido a fuerzas funcionales y disfuncionales en diferentes direcciones. Se buscó comprender, bajo las variables contempladas, las zonas de concentración de esfuerzos que conllevan al daño estructural de sus constituyentes y tejidos adyacentes. Se realizó el modelo 3D de la reconstrucción de un archivo TAC de un primer premolar inferior, que incluyó esmalte, dentina, ligamento periodontal y hueso alveolar considerando tres variables: dirección, magnitud y área de la fuerza aplicada. La dirección fue dirigida en tres vectores (vertical, tangencial y horizontal) bajo cuatro magnitudes, una funcional de 35 N y tres disfuncionales de 170, 310 y 445 N, aplicadas sobre un área de la cara oclusal y/o vestibular del premolar que involucró tres contactos estabilizadores (A, B y C) y dos paradores de cierre. Los resultados obtenidos explican el fenómeno de combinar tres vectores, cuatro magnitudes y un área de aplicación de la fuerza, donde los valores de esfuerzo efectivo equivalente Von Mises muestran valores máximos a partir de los 60 MPa. Los valores de tensión máximos se localizan, bajo la carga horizontal a 170 N y en el proceso masticatorio en la zona cervical, cuando la fuerza pasa del 60 %. Sobre la base de los hallazgos de este estudio, se puede concluir que la reacción de los tejidos a fuerzas funcionales y disfuncionales varía de acuerdo con la magnitud, dirección y área de aplicación de la fuerza. Los valores de tensión resultan ser más altos bajo la aplicación de fuerzas disfuncionales tanto en magnitud como en dirección, produciendo esfuerzos tensiles significativos para la estructura dental y periodontal cervical, mientras que, bajo las cargas funcionales aplicadas en cualquier dirección, no se generan esfuerzos lesivos. Esto supone el reconocimiento del poder de detrimento estructural del diente y periodonto frente al bruxismo céntrico y excéntrico.

SUMMARY: The purpose of this study was to analyze the mechanical behavior of the healthy dental structure of a human mandibular first premolar subjected to functional and dysfunctional forces in different directions. It was sought to understand, under the contemplated variables, the areas of stress concentration that lead to structural damage of its constituents and adjacent tissues. The 3D model of the reconstruction of a CT file of a lower first premolar was made, which included enamel, dentin, periodontal ligament and alveolar bone considering three variables: direction, magnitude and area of the applied force. The direction was directed in three vectors (vertical, tangential and horizontal) under four magnitudes, one functional of 35 N and three dysfunctional of 170, 310 and 445 N, applied to an area of the occlusal and/or buccal face of the premolar that involved three stabilizing contacts (A, B and C) and two closing stops. The results obtained explain the phenomenon of combining three vectors, four magnitudes and an area of force application, where the values of effective equivalent Von Mises stress show maximum values from 60 MPa. The maximum tension values are located under the horizontal load at 170 N and in the masticatory process in the cervical area, when the force exceeds 60%. Based on the findings of this study, it can be concluded that the reaction of tissues to functional and dysfunctional forces varies according to the magnitude, direction, and area of application of the force. The stress values turn out to be higher under the application of dysfunctional forces both in magnitude and in direction, producing significant tensile stresses for the dental and cervical periodontal structure, while under functional loads applied in any direction, no damaging stresses are generated. This supposes the recognition of the power of structural detriment of the tooth and periodontium against centric and eccentric bruxism.

Influência da profundidade e de um processo de envelhecimento acelerado em propriedades de resinas bulk fill / Influence of depth and an accelerated aging process on bulk fill resin properties

O presente estudo teve como objetivo avaliar o desempenho de quatro resinas bulk fill (Filtek Bulk Fill (FBF), Opus Bulk Fill (OBF), Sonicfill (SF) e Tetric N-Ceram Bulk Fill (TNBF)) e uma resina convencional (Charisma Diamond (CD)) quanto às seguintes propriedades: resistência à flexão (RF), módulo de elasticidade (ME) e dureza Knoop (KHN) em função da profundidade e após a realização de um envelhecimento acelerado. Corpos de prova em formato de barra foram confeccionados simultaneamente em diferentes profundidades (1, 2, 3, 4 e 5 mm) para realização dos testes de resistência à flexão (n=10), módulo de elasticidade (n=10) e dureza Knoop (n=3). Os testes foram realizados em dois momentos, previamente e após a realização de um envelhecimento acelerado, que consistiu na realização de uma termociclagem com banhos alternados em água a 5 e 55ºC, com 1 min de imersão em cada, por 2000 ciclos. Os resultados para o teste de RF e ME mostraram que os valores para estas duas propriedades diminuíram em função da profundidade e após a realização da termociclagem para todas as resinas estudadas. Apenas a resina TNBF não apresentou diferença estatística para valores de ME após o envelhecimento acelerado. Quanto à dureza, os valores também diminuíram em função da profundidade, porém aumentaram após a realização do envelhecimento acelerado. Apenas a resina SF não apresentou diferença estatística entre os valores de dureza antes e após o envelhecimento. A resina convencional CD após a ciclagem térmica foi a única que apresentou relação base/topo (2 mm) acima de 80%. Nenhuma das resinas do tipo bulk fill apresentou uma relação base/topo acima de 80% para a dureza quando avaliadas na espessura máxima recomendada. Com base nos resultados obtidos, pode-se afirmar que, quando fotoativadas na espessura máxima recomendada, apenas a resina convencional CD apresentou resultados condizentes com a homogeneidade esperada em todas as condições deste estudo. Entretanto, para as resinas do tipo bulk fill, pode-se observar que as propriedades estudadas, de modo geral, sofreram uma diminuição significativa em função da profundidade. Para o envelhecimento, a dureza, diferentemente dos outros parâmetros, mostrou uma tendência de aumento.

Study of nonlinear viscoelastic mechanical properties of degenerated intervertebral discs / Estudio de las propiedades mecánicas viscoelásticas no lineales de discos intervertebrales degenerados

SUMMARY: Biomechanical factors are important factors in inducing intervertebral disc degeneration, in this paper, the nonlinear viscoelastic mechanical properties of degenerated intervertebral discs were analyzed experimentally. Firstly, the loading and unloading curves of intervertebral discs before and after degeneration at different strain rates were compared to analyze the changes of their apparent viscoelastic mechanical properties; The internal stress/strain distribution of the disc before and after degeneration was then tested by combining digital image technology and fiber grating technology. The results show that the intervertebral disc is strain-rate- dependent whether before or after degeneration; The modulus of elasticity and peak stress of the degenerated disc are significantly reduced, with the modulus of elasticity dropping to 50 % of the normal value and the peak stress decreasing by about 55 %; Degeneration will not change the distribution of the overall internal displacement of the intervertebral disc, but has a greater impact on the superficial and middle AF; The stress in the center of the nucleus pulposus decreases, and the stress in the outer AF increases after degeneration. Degeneration has a great impact on the nonlinear viscoelastic mechanical properties of intervertebral disc, which has reference value for the mechanism, treatment and prevention of clinical degenerative diseases.

RESUMEN: Los factores biomecánicos son importantes en la inducción de la degeneración del disco intervertebral. En este estudio se analizaron experimentalmente las propiedades mecánicas viscoelásticas no lineales de los discos intervertebrales degenerados. En primer lugar se compararon las curvas de carga y descarga de los discos intervertebrales, antes y después de la degeneración, a diferentes velocidades de deformación para analizar los cambios aparentes de sus propiedades mecánicas viscoelásticas. La distribución interna de tensión/deformación del disco antes y después de la degeneración se probó luego combinando tecnología de imagen digital y tecnología de rejilla de fibra. Los resultados mostraron que el disco intervertebral depende de la velocidad de deformación antes o después de la degeneración; El módulo de elasticidad y la tensión máxima del disco degenerado se reducen significativamente, cayendo el módulo de elasticidad al 50 % del valor normal y la tensión máxima disminuyendo en aproximadamente un 55 %; La degeneración no cambiará la distribución del desplazamiento interno general del disco intervertebral, pero tiene un mayor impacto en la FA superficial y media; El estrés en el centro del núcleo pulposo disminuye y el estrés en el FA externo aumenta después de la degeneración. La degeneración tiene un gran impacto en las propiedades mecánicas viscoelásticas no lineales del disco intervertebral, que tiene valor de referencia para el mecanismo, tratamiento y prevención de enfermedades clínicas degenerativas.

The detection and evaluation of vascular stiffness / 生理学报

Cardiovascular homeostasis is regulated by both physical and chemical factors. Vascular stiffness, a physical property of vessel, is crucial in maintaining the physiological function of vasculature. Vascular stiffness has been indicated to be correlated with hypertension, heart failure and other cardiovascular diseases. It has been the most widely accepted clinical index for assessment of vascular function and dysfunction. This paper reviews the commonly used experimental and clinical techniques for evaluating vascular stiffness including direct detection of the Young's modulus and indirect detection method that is based on ultrasound technique and others. Principles of these methodologies, as well as their advantages and disadvantages, are also presented here. Researchers and clinical staff are encouraged to choose the most suitable methods for detecting vascular stiffness according to their purposes and objects, so as to effectively evaluate vascular function.

Incorporation of a polymerization catalyst for improved mechanical behavior and physicochemical characteristics of a light-cured pulp capping material / Incorporação de um catalisador de polimerização para aprimorar propriedades mecânicas e fisíco-químicas de um protetor pulpar fotoativável

Objective: To evaluate the influence of the incorporation of a polymerization catalyst to a light-cured pulp capping material on mechanical behavior and physicochemical characteristics. Material and Methods: Different percentages (2 wt%, and 4 wt%) of diphenyliodonium hexafluorophosphate (DPI) were incorporated into the Ultra-Blend Plus, a resin-modified calcium-based cement. The material without incorporation of DPI (0 wt%) served as control. Degree of Conversion (DC), Flexural Strength (FS), Elastic Modulus (EM), Water Sorption (WSp), Solubility (Sl), and pH of eluate at 24-h, 72-h, and 7-day storage times were measured. One-way ANOVA/Tukey posthoc tests were used to analyze the data (p <0.05). Results: For DC, FS, and EM, materials with different % of DPI showed statistically significant differences, so that 0% provided the lowest values and 2% the highest values. Materials with 0% and 2% of DPI provided statistically the lowest WSp, whilst material with 0% of DPI showed statistically the highest Sl. Conclusion: All materials provided statistically similar pH to eluates regardless of storage time, although only materials with DPI at 2% and 4% maintained pH of eluates statistically similar from 72 h to 7 days storage times.(AU)

Objetivo: avaliar a influência nas propriedades mecânicas e físico-químicas da incorporação de um catalisador de polimerização a um protetor pulpar fotoativável. Material e Métodos: foram adicionadas diferentes porcentagens em massa (2% e 4%) de hexafluorofosfato de difeniliodônio (DPI) ao Ultra-Blend Plus, um cimento à base de hidróxido de cálcio modificado por resina. O material sem a adição do DPI (0%) serviu como controle. Foram avaliados: Grau de Conversão (DC), Resistência Flexural (FS), Módulo de Elasticidade (EM), Sorção (WSp), Solubilidade (SI) e o pH do eluato nos tempos de 24h, 72h e 7 dias de armazenamento. ANOVA 1-way com pós-teste de Tukey (p <0.05). Foi utilizado para avaliar os resultados estatisticamente. Resultados: Os materiais com diferentes % de DPI apresentaram diferenças significativas para os testes de DC, FS e EM. A porcentagem em massa de 0% de DPI mostrou valores inferiores a todos os testados e os materiais com adição 2% apresentaram a melhor performance. Materiais com 0% e 2% de DPI apresentaram valores inferiores de WSp; a porcentagem de 0% proporcionou valores estatisticamente maiores para SI. Conclusão: Todos os materiais testados apresentaram pH semelhante nos eluatos independente do tempo de armazenamento, contudo, apenas os materiais com 2% e 4% mantiveram o pH dos eluatos estatisticamente similares nos tempos de estocagem de 72h a 7 dias.(AU)

Comparación del módulo de elasticidad y resistencia de la resina acrílica de termocurado y la resina flexible superpoliamida. Estudio in vitro / Comparison of the module of elasticity and resistance of thermal curing acrylic resin and flexible superpolyamide resin. An in vitro study

Objetivo: Comparar el módulo de elasticidad y resistencia de la resina acrílica de termocurado y la resina flexible superpoliamida. Métodos: Se diseñó un estudio experimental que empleó dos tipos de resinas acrílicas preparadas en cera para obtener una forma rectangular de 64 mm de largo, 10 mm de ancho y 2,5 mm de grosor, pasadas a acrílico de termocurado y resina flexible superpoliamida. Se emplearon 10 bloques de resina acrílica de cada tipo sometidas a compresión por la máquina de ensayos universal, que generó una fuerza de aproximación de 0,001 N sobre los bloques con un avance de 0,01 mm/min. El módulo de resistencia y el módulo de elasticidad se analizaron mediante la prueba de flexión de tres puntos. Resultados: El módulo de elasticidad de la resina acrílica de termocurado fue de 2501,83 ± 139,42, mientras que el módulo de resistencia fue de 78,36 ± 11,69 MPa. Por otro lado, el módulo de elasticidad de la resina flexible superpoliamida fue de 1020,59 ± 92,95, mientras que el módulo de resistencia fue de 36,04 ± 2,71 MPa. El módulo de elasticidad de la resina acrílica de termocurado fue mayor al de la resina flexible superpoliamida, esta diferencia fue de 1481,24 MPa. El módulo de resistencia de la resina acrílica de termocurado fue mayor al de la resina flexible superpoliamida. Conclusiones: Se concluyó que el módulo de elasticidad (rigidez) y resistencia fue mayor en la resina acrílica de termocurado en comparación a la resina flexible superpoliamida(AU)

Objective: Compare the module of elasticity and resistance of thermal curing acrylic resin and flexible superpolyamide resin. Methods: An experimental study was conducted of two types of acrylic resins molded in wax to obtain a 64 mm long, 10 mm wide and 2.5 mm thick rectangular shape, and then transferred to thermal curing acrylic resin and flexible superpolyamide resin. Ten acrylic resin blocks of each type were used. The blocks were compressed by the universal testing machine, which generated an approximation force of 0.001 N on the blocks at a forward speed of 0.01 mm/min. The resistance module and the elasticity module were analyzed with the three point flexural test. Results: The elasticity module of the thermal curing acrylic resin was 2501.83 ± 139.42, whereas the resistance module was 78.36 ± 11.69 MPa. The elasticity module of the flexible superpolyamide resin was 1020.59 ± 92,95, whereas the resistance module was 36.04 ± 2.71 MPa. The elasticity module of the thermal curing acrylic resin was greater than that of the flexible superpolyamide resin, the difference being 1481.24 MPa. The resistance module of the thermal curing acrylic resin was greater than that of the flexible superpolyamide resin. Conclusions: The elasticity (rigidity) and resistance module was greater in the thermal curing acrylic resin than in the flexible superpolyamide resin(AU)

Prediction Method of Elastic Modulus of Trabecular Bone Based on SE-DenseVoxNet / 中国医疗器械杂志

Osteoporosis is one of the common metabolic diseases, which can easily lead to osteoporotic fractures. Accurate prediction of bone biomechanical properties is of great significance for the early prevention and diagnosis of osteoporosis. Bone mineral density measurement is currently used clinically as the gold standard for assessing bone strength and diagnosing osteoporosis, but studies have shown that bone mineral density can only explain 60% to 70% of bone strength changes, and trabecular bone microstructure is an important factor affecting bone strength. In order to establish the connection between trabecular bone microstructure and bone strength, this paper proposes a prediction method of trabecular bone modulus based on SE-DenseVoxNet. This method takes three-dimensional binary images of trabecular bone as input and predicts its elastic modulus in the z-axis direction. Experiments show that the error and bias between the predicted value of the method and the true value of the sample are small and have good consistency.

Effect of antioxidant agents after dental bleaching on luting of ceramic laminates / Efeito de agentes antioxidantes pós-clareamento na cimentação de laminados cerâmicos

O objetivo deste estudo in vitro foi avaliar o efeito da aplicação de agentes antioxidantes após o clareamento dentário e previamente à cimentação de laminados cerâmicos na estabilidade cromática do conjunto restaurador, assim como nas propriedades mecânicas de nanodureza (HIT), módulo de elasticidade (Eit*), grau de conversão, resistência de união e morfologia da interface adesiva. Ademais, a neutralização de peróxido de hidrogênio e a caracterização superficial do esmalte, como ângulo de contato, energia de superfície, energia livre total de interação, microscopia eletrônica de varredura e espectroscopia de energia dispersiva do substrato submetido à ação das soluções antioxidantes e do agente clareador também foram analisados. Duzentos e quarenta e dois blocos de esmalte dentário (7x8x0,6mm) foram utilizados para o processo de cimentação e distribuídos em grupos experimentais de acordo com os métodos de procedimentos (grupo não clareado, grupo clareado com Whiteness HP Maxx 35%), tipos de antioxidantes adotados (controle; ácido ascórbico 10% e α-tocoferol 10%) e períodos de cimentação (após 24 horas e 14 dias do processo de cimentação) (n = 22). Foi utilizado o sistema adesivo Tetric N Bond Universal e o cimento resinoso Variolink Esthetic LC (Ivoclar Vivadent) como agentes cimentantes. Os dados foram submetidos a testes estatísticos de normalidade e analisados por ANOVA e teste de Tukey (α = 0,05). Os dados da morfologia da interface adesiva, obtidas pela microscopia confocal a laser, foram submetidas ao teste Kappa inter-examinadores e os dados foram submetidos aos testes Kruskal-Wallis e Dunn (α = 0,05). Os resultados mostraram que, de modo geral, a utilização da solução antioxidante α-tocoferol 10% pós-clareamento no período mediato promoveu resultados satisfatórios com relação à estabilidade cromática do conjunto restaurador, assim como para as propriedades mecânicas, grau de conversão, resistência de união e morfologia da interface adesiva comparado ao grupo clareado sem associação dos agentes antioxidantes, tanto para o período mediato, quanto para o período de 14 dias (p< 0,05). A solução de αtocoferol 10% apresentou maiores valores de neutralização do peróxido de hidrogênio e maiores valores de molhabilidade do esmalte em relação aos grupos controle e ácido ascórbico (p< 0,05). A energia de superfície e energia livre total de interação do esmalte dentário foi significativamente influenciada pelo tratamento clareador (p< 0,05). Dessa forma, conclui-se que o emprego da solução antioxidante α-tocoferol 10% promoveu resultados promissores, sugerindo que o mesmo poderia ser utilizado mediatamente após o clareamento dental na cimentação de laminados cerâmicos(AU)

The aim of this in vitro study was to evaluate the effect of antioxidant agents application after tooth bleaching and prior to luting of ceramic veneers on color stability of the restorative set, as well as on mechanical properties of nanohardness (HIT), elastic modulus (Eit*), degree of conversion, bond strength and morphology of the adhesive interface. Furthermore, the hydrogen peroxide neutralization and surface characterization of enamel, such as contact angle, surface energy, total free energy of interaction, scanning electron microscopy and energy-dispersive spectroscopy of the substrate submitted to the action of antioxidant solutions and bleaching agent were also analyzed. Two hundred forty two dental enamel blocks (7 x 8 x 0.6 mm) were used for the luting process and distributed into experimental groups according to the procedure methods (unbleached group, bleached group with Whiteness HP Maxx 35%), types of antioxidants adopted (control; 10% ascorbic acid and 10% α-tocopherol) and the luting periods (24 hours and 14 days after the luting process) (n = 22). Tetric N Bond Universal adhesive system and Variolink Esthetic LC resin cement (Ivoclar Vivadent) were used as luting agents. Data were submitted to statistical tests of normality and analyzed by ANOVA and Tukey tests (α = 0.05). The adhesive interface morphology data, obtained by confocal laser microscopy, were submitted to the interexaminer Kappa test and the data were submitted to Kruskal-Wallis and Dunn´s tests (α = 0.05). The results showed that, in general, the use of 10% α-tocopherol antioxidant solution after bleaching in mediate period promoted satisfactory results regarding the color stability of the restorative set, as well as for the mechanical properties, degree of conversion, shear bond strength and adhesive interface morphology compared to the bleached group without antioxidant agents association, both for the mediate and 14-day period (P < 0.05). The 10% αtocopherol solution showed higher hydrogen peroxide neutralization values and higher enamel wettability values compared to the control and ascorbic acid groups (P < 0.05). Surface energy and total free energy of interaction of tooth enamel were significantly influenced by the bleaching treatment (P < 0.05). Thus, it is concluded that the use of 10% αtocopherol antioxidant solution promoted promising results, suggesting that it could be used mediately after tooth bleaching on luting of ceramic laminates(AU)

Quantitative Evaluation of Sciatic Nerve Crush Injury with Conventional Ultrasound Combined with Shear-wave Elastography in Rabbit Models / 中国医学科学院学报

To explore the value of conventional ultrasound combined with shear-wave elastography in the quantitative evaluation of sciatic nerve crush injury in rabbit models. Forty healthy male New Zealand white rabbits were randomly divided into four groups (=10 in each group):three crush injury (CI) groups (2,4,and 8 weeks after crush) and control group (without injury). The thickness and stiffness of the crushed sciatic nerves and denervated triceps surae muscles were measured at different time points and compared with histopathologic parameters. Inter-reader variability was assessed with intraclass correlation coefficients. Compared with the control group,the inner diameters of the sciatic nerves significantly increased in the 2-week CI group [(1.65±0.34) mm (0.97±0.15) mm,=0.00] but recovered to the nearly normal level in the 8-week CI group [(1.12±0.18) mm (0.97±0.15) mm,=0.06];however,compared with control group [(8.75±1.02)kPa],the elastic modulus of the nerves increased significantly in all the CI groups [2-week:(14.77±2.53) kPa;4-week:(19.12±3.46) kPa;and 8-week:(28.39±5.26) kPa;all =0.00];pathologically,massive hyperplasia of collagen fibers were found in the nerve tissues. The thickness of denervated triceps surae muscle decreased gradually,and the elastic modulus decreased 2 weeks after injury but increased gradually in the following 6 weeks;pathologically,massive hyperplasia of collagen fibers and adipocytes infiltration were visible,along with decreased muscle wet-weight ratio and muscle fiber cross-sectional area. The inter-reader agreements were good. Conventional ultrasound combined with shear-wave elastography is feasible for the quantitative evaluation of the morphological and mechanical properties of crushed nerves and denervated muscles.

Increased elastic modulus of the synovial membrane in a rat ACLT model of osteoarthritis revealed by atomic force microscopy

This study aimed to explore changes in nanoscale elastic modulus of the synovium using atomic force microscopy (AFM) in addition to investigate changes in synovial histomorphology and secretory function in osteoarthritis (OA) in a rat anterior cruciate ligament transection (ACLT) model. Sprague-Dawley rats were randomly assigned to sham control and ACLT OA groups. All right knee joints were harvested at 4, 8, or 12 weeks (W) after surgery for histological assessment of cartilage damage and synovitis in both the anterior and posterior capsules. AFM imaging and nanoscale biomechanical testing were conducted to measure the elastic modulus of the synovial collagen fibrils. Immunohistochemistry was used to visualize the expression of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and matrix metalloproteinase-3 (MMP-3) in the synovium. The OA groups exhibited progressive development of disease in the cartilage and synovium. Histopathological scores of the synovium in the OA groups increased gradually. Significant differences were observed between all OA groups except for the posterior 4W group. The synovial fibril arrangement in all OA groups was significantly disordered. The synovial fibrils in all ACLT OA groups at each time point were stiffer than those in the sham controls. OA rats displayed a significantly higher expression of IL-1β and MMP3 in the anterior capsule. In summary, synovial stiffening was closely associated with joint degeneration and might be a factor contributing to synovitis and increased production of proinflammatory mediators. Our data provided insights into the role of synovitis, particularly stiffening of the synovium, in OA pathogenesis.

Can composition and preheating improve infiltrant characteristics and penetrability in demineralized enamel?

Abstract The composition of infiltrants can influence their physical properties, viscosity and depth of penetration (DP). Strategies are used to increase the DP, such as the addition of diluents or the use of heat. This study aimed to evaluate the effect of preheating and composition on physical properties and DP of infiltrants in demineralized enamel. The groups were assigned, and the following experimental formulations were made: 25%BisEMA +75%TEGDMA; 25%BisEMA +65%TEGDMA +10%ethanol; 25%BisEMA +65%TEGDMA +10%HEMA; 100%TEGDMA; 90%TEGDMA +10%ethanol; 90%TEGDMA +10%HEMA. The samples were photoactivated at two temperatures (25°C and 55°C). Degree of conversion (DC) was performed using an infrared spectrophotometer. Elastic modulus (E), flexural strength (FS) and contact angle (CA) tests were also performed. The DP of an infiltrant in demineralized enamel was determined by confocal laser scanning microscopy (CLSM) using an indirect labeling technique. The data were analyzed by two-way ANOVA and Tukey's test. DC increased after preheating in all the groups; however, 90%TEGDMA+10%ethanol showed the lowest DC for both temperatures, and the lowest E. Preheating did not influence E or FS. The CA increased at 55°C for most groups, but decreased for groups containing HEMA. Temperature did not seem to influence DP, and Icon showed the lowest DP values. The 100%TEGDMA composition showed more homogeneous penetration, whereas Icon showed heterogeneous and superficial penetration. The preheating technique does not improve all properties in all the material compositions. The composition of a material can influence and improve its properties.

The effect of regions-of-interest and elasticity modulus selection on differentiating benign and malignant cervical lymph nodes with shear wave elastography

OBJECTIVE: Imaging diagnosis of cervical lymphadenopathy has conventionally used ultrasonography. Shear wave elastography (SWE) is a recent ultrasound technological advancement that has shown promise in the important medical problem of differentiating between benign and malignant cervical lymph nodes based on quantitative measurements of elasticity modulus. However, widely varying elasticity modulus metrics and regions-of-interest (ROIs) were used in existing studies, leading to inconsistent findings and results that are hard to compare with each other. METHODS: Using a large dataset of 264 cervical lymph nodes from 200 patients, we designed a study comparing three elasticity modulus metrics (Emax, Emean, and standard deviation-SD) with three different ROIs to evaluate the effect of such selections. The metric values were compared between the benign and malignant node groups. The different ROI and metric selections were also compared through receiver operating characteristics curve analysis. RESULTS: For all ROIs, all metric values were significantly different between the two groups, indicting their diagnostic potential. This was confirmed by the ≥0.80 area under the curve (AUC) values achieved with these metrics. Different ROIs had no effect on Emax, whereas all ROIs achieved high performance at 0.88 AUC. For Emean, the smallest ROI focusing on the area of the highest elasticity achieved the best diagnostic performance. In contrast, the larger ROIs achieved higher performances for SD. CONCLUSIONS: This study illustrated the effect of elasticity modulus and ROI selection on the diagnostic performance of SWE on cervical lymphadenopathy. These new findings help guide relevant future studies and clinical applications of this important quantitative imaging modality.

Direct resin composite restoration of endodontically-treated permanent molars in adolescents: bite force and patient-specific finite element analysis

Abstract Objective To evaluate the influence of three levels of dental structure loss on stress distribution and bite load in root canal-treated young molar teeth that were filled with bulk-fill resin composite, using finite element analysis (FEA) to predict clinical failure. Methodology Three first mandibular molars with extensive caries lesions were selected in teenager patients. The habitual occlusion bite force was measured using gnathodynamometer before and after endodontic/restoration procedures. The recorded bite forces were used as input for patient-specific FEA models, generated from cone-beam computed tomographic (CT) scans of the teeth before and after treatment. Loads were simulated using the contact loading of the antagonist molars selected based on the CT scans and clinical evaluation. Pre and post treatment bite forces (N) in the 3 patients were 30.1/136.6, 34.3/133.4, and 47.9/124.1. Results Bite force increased 260% (from 36.7±11.6 to 131.9±17.8 N) after endodontic and direct restoration. Before endodontic intervention, the stress concentration was located in coronal tooth structure; after rehabilitation, the stresses were located in root dentin, regardless of the level of tooth structure loss. The bite force used on molar teeth after pulp removal during endodontic treatment resulted in high stress concentrations in weakened tooth areas and at the furcation. Conclusion Extensive caries negatively affected the bite force. After pulp removal and endodontic treatment, stress and strain concentrations were higher in the weakened dental structure. Root canal treatment associated with direct resin composite restorative procedure could restore the stress-strain conditions in permanent young molar teeth.

Mechanical and Mechanosensing Properties of Tumor Affected Bone Cells Were Inhibited via PI3K/Akt Pathway

BACKGROUND: Osteolytic metastasis is a common destructive form of metastasis, in which there is an increased bone resorption but impaired bone formation. It is hypothesized that the changed mechanical properties of tumor affected bone cells could inhibit its mechanosensing, thus contributing to differences in bone remodeling. METHODS: Here, atomic force microscopy indentation on primary bone cells exposed to 50% conditioned medium from Walker 256 (W) carcinoma cell line or its adaptive tumor (T) cells was carried out. Nitric oxide levels of bone cells were monitored in response to low-magnitude, high-frequency (LMHF) vibrations. RESULTS: A stronger sustained inhibitive effect on bone cell viability and differentiation by T cells as compared to that of its cell line was demonstrated. This could be attributed to the higher levels of transforming growth factor-β1 (TGF-β1) in the T-conditioned medium as compared to W-conditioned medium. Bone cell elastic moduli in W and T-groups were found to decrease significantly by 61.0% and 69.6%, respectively compared to control and corresponded to filamentous actin changes. Nitric oxide responses were significantly inhibited in T-conditioned group but not in W-conditioned group. CONCLUSIONS: It implied that a change in cell mechanical properties is not sufficient as an indicator of change in mechanosensing ability. Moreover, inhibition of phosphoinositide 3-kinase/Akt downstream signaling pathway of TGF-β1 alleviated the inhibition effects on mechanosensing in T-conditioned cells, further suggesting that growth factors such as TGF-β could be good therapeutic targets for osteoblast treatment.

Shear-Wave and Strain Ultrasound Elastography of the Supraspinatus and Infraspinatus Tendons in Patients with Idiopathic Adhesive Capsulitis of the Shoulder: A Prospective Case-Control Study

OBJECTIVE: To compare the elasticity of the supraspinatus tendon (SST) and infraspinatus tendon (IST) in patients with idiopathic adhesive capsulitis of the shoulder (ACS) with those in the control groups and to evaluate the relationship between age and tendon elasticity. MATERIALS AND METHODS: The Institutional Review Board approved this prospective, case-control study, which was conducted between November 2017 and March 2018, and informed consent was obtained from all participants. Control groups comprised healthy individuals or those with asymptomatic contralateral shoulders. Twenty-five shoulders in 20 participants in the ACS group (14 women; 53.5 ± 7.9 years) and 24 shoulders in 18 participants in the control group (6 women; 52.6 ± 10.5 years) were included. Elastography was performed in the oblique coronal plane at the neutral shoulder position. Mean/maximum/minimum velocity and stiffness from the shear-wave ultrasound elastography (SWE) and strain ratio (subcutaneous fat/target-tendon) from the strain ultrasound elastography (SE) of the SST and IST were evaluated. Statistical analyses were performed using the Mann-Whitney U test, receiver operating characteristic (ROC) curve, and Spearman correlation. RESULTS: Both velocity and stiffness in SWE were higher, and the strain ratio in SE was lower in participants with symptomatic shoulders than in those with normal shoulders (p 0.970). The elastic modulus was little correlated with age (ρ = −0.340–0.239). CONCLUSION: SWE and SE indicated that SST and IST were stiffer in patients with ACS than in those with normal shoulders regardless of aging.

Compliant substratum modulates vinculin expression in focal adhesion plaques in skeletal cells / 国际口腔科学杂志·英文版

The biophysical properties of the extracellular matrix (ECM) dictate tissue-specific cell behaviour. In the skeleton system, bone shows the potential to adapt its architecture and contexture to environmental rigidity via the bone remodelling process, which involves chondrocytes, osteoblasts, osteoclasts, osteocytes and even peripheral bone marrow-derived stem/stromal cells (BMSCs). In the current study, we generated stiff (~1 014 ± 56) kPa, Young's modulus) and soft (~46 ± 11) kPa silicon-based elastomer polydimethylsiloxane (PDMS) substrates by mixing curing agent into oligomeric base at 1:5 and 1:45 ratios, respectively, and investigated the influence of substrate stiffness on the cell behaviours by characterizing cell spreading area, cell cytoskeleton and cell adhesion capacity. The results showed that the cell spreading areas of chondrocytes, osteoblasts, osteoclasts, osteocytes and BMSCs were all reduced in the soft substrate relative to those in the stiff substrate. F-actin staining confirmed that the cytoskeleton was also changed in the soft group compared to that in the stiff group. Vinculin in focal adhesion plaques was significantly decreased in response to soft substrate compared to stiff substrate. This study establishes the potential correlation between microenvironmental mechanics and the skeletal system, and the results regarding changes in cell spreading area, cytoskeleton and cell adhesion further indicate the important role of biomechanics in the cell-matrix interaction.

Experimental study on mechanical properties of the ventral and the dorsal tissues of porcine descending aorta / 生物医学工程学杂志

The mechanical properties of the aorta tissue is not only important for maintaining the cardiovascular health, but also is closely related to the development of cardiovascular diseases. There are obvious differences between the ventral and dorsal tissues of the descending aorta. However, the cause of the difference is still unclear. In this study, a biaxial tensile approach was used to determine the parameters of porcine descending aorta by analyzing the stress-strain curves. The strain energy functions Gasser-Ogden-Holzapfel was adopted to characterize the orthotropic parameters of mechanical properties. Elastic Van Gieson (EVG) and Sirius red stain were used to observe the microarchitecture of elastic and collagen fibers, respectively. Our results showed that the tissue of descending aorta had more orthotropic and higher elastic modulus in the dorsal region compared to the ventral region in the circumferential direction. No significant difference was found in hyperelastic constitutive parameters between the dorsal and ventral regions, but the angle of collagen fiber was smaller than 0.785 rad (45°) in both dorsal and ventral regions. The arrangement of fiber was inclined to be circumferential. EVG and Sirius red stain showed that in outer-middle membrane of the descending aorta, the density of elastic fibrous layer of the ventral region was higher than that of the dorsal region; the amount of collagen fibers in dorsal region was more than that of the ventral region. The results suggested that the difference of mechanical properties between the dorsal and ventral tissues in the descending aorta was related to the microstructure of the outer membrane of the aorta. In the relatively small strain range, the difference in mechanical properties between the ventral and dorsal tissues of the descending aorta can be ignored; when the strain is higher, it needs to be treated differently. The results of this study provide data for the etiology of arterial disease (such as arterial dissection) and the design of artificial blood vessel.

Evaluation of bovine pericardium performance after liquid nitrogen freezing and thinning / 生物医学工程学杂志

In the present study, the performance of the liquid nitrogen frozen and thinned bovine pericardium was studied and compared with the porcine pericardium. The microstructure and mechanical properties of the bovine pericardium were observed and tested by hematoxylin-eosin (HE) staining and tensile test respectively. In all conditions, porcine pericardium was selected as a control group. The results showed that there was little difference in the performance of bovine pericardium after being frozen by liquid nitrogen. The secant modulus and ultimate strength of the thinned bovine pericardium were similar to those of porcine pericardium, however, the elastic modulus was a little higher than porcine pericardium. The study suggested that the performance of the thinned bovine pericardium was similar to those of porcine pericardium. It was easy for the thinned bovine pericardium to obtain a relatively ideal thickness and expected performance, therefore, the thinned bovine pericardium can be used as the materials of transcatheter aortic valve leaflets.