Effect of elastomeric urethane monomer on physicochemical properties and shrinkage stress of resin composites

Abstract This study aimed to evaluate the effect of an elastomeric urethane monomer (Exothane-24) in different concentrations on physicochemical properties, gap formation, and polymerization shrinkage stress of experimental resin composites. All experimental composites were prepared with 50 wt.% of Bis-GMA and 50 wt.% of TEGDMA, to which 0 wt.% (control), 10 wt.%, 20 wt.%, 30 wt.%, and 40 wt.% of Exothane-24 were added. Filler particles (65 wt.%) were then added to these resin matrixes. Ultimate tensile strength (UTS: n = 10), flexural strength (FS: n = 10), flexural modulus (FM: n = 10), hardness (H: n = 10), hardness reduction (HR: n = 10), degree of conversion (DC: n = 5), gap width (GW: n = 10), and polymerization shrinkage stress in Class I (SS-I: n = 10) and Class II (SS-II: n = 10) simulated configuration. All test data were analyzed using one-way ANOVA and Tukey's test (α = 0.05; β= 0.2). Exothane-24 in all concentrations decreased the H, HR, DC, GW, SS-I, and SS-II (p < 0.05) without affecting the UTS, and FS (p > 0.05). Reduction in FM was observed only in the Exothane 40% and 30% groups compared to the control (p < 0.05). Exothane-24 at concentrations 20% and 30% seems suitable since it reduced GW and polymerization SS without affecting the properties of the composite resins tested, except for H.

Resumo Este estudo teve como objetivo avaliar o efeito de um monômero elastomérico de uretano (Exothane-24) em diferentes concentrações em propriedades físico-químicas, formação de fenda e tensão de contração de polimerização de resinas compostas experimentais. Todos os compósitos experimentais foram preparados com 50% em peso de Bis-GMA e 50% em peso de TEGDMA, nos quais 0% (controle), 10%, 20%, 30% e 40% em peso de Exothane-24 foram adicionados. Partículas de carga (65% em peso) foram então adicionadas as matrizes resinosas. Resistência coesiva (RC: n = 10), resistência à flexão (RF: n = 10), módulo de flexão (MF: n = 10), dureza (D: n = 10), redução de dureza (RD: n = 10), grau de conversão (GC: n = 5), largura de fenda (LF: n = 10) e tensão de contração de polimerização em simulações de cavidades Classe I (TC-I: n = 10) e Classe II (TC-II: n = 10). Todos os dados do teste foram analisados usando one-way ANOVA e teste de Tukey (α = 0,05; β = 0,2). O Exothane-24 em todas as concentrações diminuiu a D, RD, GC, LF, TC-I e TC-II (p < 0,05) sem afetar o RC e RF (p > 0,05). A redução da MF foi observada apenas nos grupos Exothane 40% e 30% em relação ao controle (p < 0,05). O Exothane-24 nas concentrações de 20% e 30% pareceu ser adequado, pois reduziu LF e TC de polimerização sem afetar as propriedades das resinas compostas testadas, exceto para D.

Tratamentos de superfície prévios à camada de caracterização: efeitos na resistência adesiva e comportamento mecânico de cerâmicas de óxido de zircônio / Surface treatments prior to the characterization layer: effects on bond strength and mechanical behavior of zirconium oxide ceramics

Este estudo avaliou o efeito do jateamento com óxido de alumínio prévio à camada de caracterização no comportamento adesivo e mecânico de zircônias de segunda e terceira gerações. Na parte A, foi realizado um estudo de resistência flexural. Para isso, discos de cada zircônia (3Y-TZP, 4Y-PSZ ou 5YPSZ) foram confeccionados. Após polimento e sinterização, os discos foram divididos de acordo com os tratamentos de superfície: Polimento, Jateamento com Al2O3 50 µm e Jateamento com Al2O3 110 µm (n = 30). A superfície tratada de todos os discos recebeu uma fina camada de pigmentação e uma fina camada de glaze. O ensaio de flexão biaxial foi realizado na configuração pistonon-three-balls e as superfícies fraturadas foram observadas em Microscopia Eletrônica de Varredura (MEV). Os dados foram submetidos à Análise de Weibull. Na parte B, avaliou-se o efeito dos diferentes tratamentos de superfície prévio à camada de caracterização no comportamento à fadiga das diferentes zircônias. Discos de 3Y-TZP, 4Y-PSZ e 5Y-PSZ foram confeccionados e distribuídos entre os tratamentos de superfície: Polimento ou Jateamento Al2O3 50 µm (n = 15), que foram realizados conforme a parte A deste estudo. Os discos foram cimentados adesivamente a um análogo de dentina (NEMA G10). Os testes de fadiga foram realizados pelo método stepwise, com aplicação de carga axial por um pistão hemisférico (carga inicial: 400 N, step: 100 N, ciclos/step: 10.000, frequência: 20 Hz). Na parte C, avaliou-se a resistência de união entre as diferentes zircônias e a camada de caracterização. Foram preparados os mesmos grupos descritos na "parte A" (n = 15). Cilindros de stain seguido por glaze foram construídos nas superfícies das zircônias. A resistência de união foi avaliada pelo teste de cisalhamento. Os tipos de falha (adesiva, predominantemente adesiva ou coesiva) foram analisados em estereomicroscópio e MEV. Análises complementares em perfilômetro e goniômetro foram realizadas. Para a parte A, o jateamento com Al2O3 110 µm aos menores valores de resistência à flexão, seguido do jateamento com as partículas de Al2O3 50 µm. Os maiores valores foram observados no grupo que não recebeu jateamento prévio à camada de caracterização. Esses resultados foram observados em todos os materiais. Na parte B, o jateamento com Al2O3 reduziu significativamente a carga e o número de ciclos para falha em fadiga de todos os materiais. Na parte C, os melhores valores de resistência de união foram atribuídos para o tratamento de superfície com Al2O3 110 µm, seguido de jateamento com Al2O3 50 µm e polimento. Dessa forma, o jateamento prévio à camada de caracterização reduz a resistência mecânica de zircônias de segunda geração e melhora a resistência de união entre os dois materiais (AU)

This study evaluated the effect of aluminum oxide sandblasting prior to the characterization layer on the adhesive and mechanical behavior of second- and third-generation zirconia. Part A consisted of a flexural strength study. Discs of each zirconia (3Y-TZP, 4Y-PSZ, or 5Y-PSZ) were prepared. After polishing and sintering, the discs were divided according to the surface treatments: Polishing, Sandblasting with Al2O3 50 µm and Sandblasting with Al2O3 110 µm (n = 30). The treated surface of all discs received a thin layer of stain and a thin layer of glaze. The biaxial bending test was performed in a piston-on-three-balls set-up. The fractured surfaces were observed by Scanning Electron Microscopy (SEM). Data were subjected to Weibull Analysis. In part B, the effect of different surface treatments prior to the characterization layer on the fatigue behavior of different zirconia was evaluated. Discs of 3Y-TZP, 4Y-PSZ and 5Y-PSZ were prepared and divided among the surface treatments: Polishing or Sandblasting Al2O3 50 µm (n = 15), which were performed according to part A of this study. The discs were adhesively cemented to a dentin-analogue (NEMA G10). Fatigue tests were performed using the stepwise method, with an axial load application by a hemispherical piston (initial load: 400 N, step: 100 N, cycles/step: 10,000, frequency: 20 Hz). Part C evaluated the bond strength between the different zirconia and the characterization layer. The same groups described in part A (n = 15) were prepared. Stain cylinders followed by glaze were built on the zirconia surfaces. The bond strength was evaluated by the shear test. The types of failure (adhesive, predominantly adhesive or cohesive) were analyzed using a stereomicroscope and SEM. Complementary analyzes in profilometer and goniometer were carried out. In part A, sandblasting with Al2O3 110 µm led to the lowest flexural strength results, followed by sandblasting with Al2O3 50 µm. Polishing group achieved the highest values. These results were observed in all tested ceramics. In part B, sandblasting with Al2O3 50 µm significantly reduced the fatigue failure load and the number of cycles for fatigue failure. In part C, the highest bond strength results were reached by sandblasting with Al2O3 110 µm, followed by sandblasting with Al2O3 50 µm, and polishing. Therefore, aluminum oxide particles sandblasting diminishes the mechanical behavior of second- and third-generation zirconias and improves the bond strength between the two materials. (AU)

Quantitative characterization of cell physiological state based on dynamical cell mechanics for drug efficacy indication / 药物分析学报

Cell mechanics is essential to cell development and function,and its dynamics evolution reflects the physiological state of cells.Here,we investigate the dynamical mechanical properties of single cells under various drug conditions,and present two mathematical approaches to quantitatively character-izing the cell physiological state.It is demonstrated that the cellular mechanical properties upon the drug action increase over time and tend to saturate,and can be mathematically characterized by a linear time-invariant dynamical model.It is shown that the transition matrices of dynamical cell systems signifi-cantly improve the classification accuracies of the cells under different drug actions.Furthermore,it is revealed that there exists a positive linear correlation between the cytoskeleton density and the cellular mechanical properties,and the physiological state of a cell in terms of its cytoskeleton density can be predicted from its mechanical properties by a linear regression model.This study builds a relationship between the cellular mechanical properties and the cellular physiological state,adding information for evaluating drug efficacy.

Study of Typical Functional Failure and Mechanical Properties of Non-absorbable Suture Anchor / 中国医疗器械杂志

OBJECTIVE@#To study the mechanical properties related to the typical functional failure modes of non-absorbable suture anchor in clinical use, and to support product design, development and verification.@*METHODS@#By retrieving the database of relevant adverse events, the typical functional failure modes of non-absorbable suture anchor were summarized, and the influencing factors of functional failure were further analyzed by studying the mechanical properties related to functional failure. The publicly available test data was retrieved for verification and provided reference for the researchers.@*RESULTS@#The typical functional failure modes of non-absorbable suture anchor include anchor failure, suture failure, fix loosening, inserter failure, which are related to the mechanical properties of products, such as screw-in torque and break torque of screw-in anchors, insertion force of knock-in anchors, suture strength, pull-out force before and after system fatigue test and elongation of sutures after fatigue test.@*CONCLUSIONS@#Enterprises should pay attention to improving the mechanical performance level of products through material, structural design and the suture weaving process to ensure the safety and effectiveness of products.

Macroscopic and mesoscopic biomechanical analysis of the bone unit in idiopathic scoliosis / 生物医学工程学杂志

To investigate the effects of postoperative fusion implantation on the mesoscopic biomechanical properties of vertebrae and bone tissue osteogenesis in idiopathic scoliosis, a macroscopic finite element model of the postoperative fusion device was developed, and a mesoscopic model of the bone unit was developed using the Saint Venant sub-model approach. To simulate human physiological conditions, the differences in biomechanical properties between macroscopic cortical bone and mesoscopic bone units under the same boundary conditions were studied, and the effects of fusion implantation on bone tissue growth at the mesoscopic scale were analyzed. The results showed that the stresses in the mesoscopic structure of the lumbar spine increased compared to the macroscopic structure, and the mesoscopic stress in this case is 2.606 to 5.958 times of the macroscopic stress; the stresses in the upper bone unit of the fusion device were greater than those in the lower part; the average stresses in the upper vertebral body end surfaces were ranked in the order of right, left, posterior and anterior; the stresses in the lower vertebral body were ranked in the order of left, posterior, right and anterior; and rotation was the condition with the greatest stress value in the bone unit. It is hypothesized that bone tissue osteogenesis is better on the upper face of the fusion than on the lower face, and that bone tissue growth rate on the upper face is in the order of right, left, posterior, and anterior; while on the lower face, it is in the order of left, posterior, right, and anterior; and that patients' constant rotational movements after surgery is conducive to bone growth. The results of the study may provide a theoretical basis for the design of surgical protocols and optimization of fusion devices for idiopathic scoliosis.

Mechanical, optical, and physicochemical properties of HPMC-based doxazosin mesylate orodispersible films

Abstract In this study, orodispersible films formed from hydroxypropyl methylcellulose (HPMC) E6 (2, 2.5, and 3%) and plasticizers ((glycerin (Gly), propylene glycol (PP), or polyethylene glycol (PEG)), containing doxazosin mesylate, were prepared by the solvent casting method and characterized. Design of experiments (DoE) was used as a statistical tool to facilitate the interpretation of the experimental data and allow the identification of optimal levels of factors for maximum formulation performance. Differential scanning calorimetry (DSC) curves and X-ray powder diffraction (XRPD) diffractograms showed doxazosin mesylate amorphization, probably due to complexation with the polymer (HPMC E6), and the glass transition temperature of the polymer was reduced by adding a plasticizer. Fourier transformed infrared (FTIR) spectroscopy results showed that the chemical structure of doxazosin mesylate was preserved when introduced into the polymer matrix, and the plasticizers, glycerin and PEG, affected the polymer matrix with high intensity. The addition of plasticizers increased the elongation at break and adhesiveness (Gly > PEG > PP), confirming the greater plasticizer effect of Gly observed in DSC and FTIR studies. Greater transparency was observed for the orodispersible films prepared using PP. The addition of citric acid as a pH modifier was fundamental for the release of doxazosin mesylate, and the desirability formulation had a release profile similar to that of the reference product

Effect of a polymerization inhibitor on the chemomechanical properties and consistency of experimental resin composites

Abstract This study investigated the effect of butylated hydroxytoluene (BHT) inhibitor on degree of conversion (DC), flexural strength (FS), flexural modulus (FM), Knoop microhardness (KH), microhardness reduction (HR), and consistency of experimental resin composites at different BHT concentrations: C0 (control-0%); C0.01 (0.01%); C0.025 (0.025%); C0.05 (0.05%); C0.1 (0.1%); and C0.5 (0.5%). For the consistency, the composites were tested immediately after being exposed to a dental chair headlight (0, 20, 40 and 60 s). Data concerning DC, FS, FM, KH, and HR were submitted to one-way ANOVA, while the consistency data was submitted to 2-way ANOVA; mean values were then compared (Tukey's test; α=0.05). The KH, FS and FM analyses showed no significant difference among the composites tested. For DC, C0 showed the highest mean value (74.2%) and differed only from C0.5 (67.2%). For HR, C0.5 showed the lowest mean (13.09%) value and differed from C0 (26.4%) and C0.01 (24.87). The consistency analysis showed no difference among C0.05, C0.1 and C0.5, considering 0 and 20 s of light exposure, while C0 (14.07 mm), C0.01 (13.97 mm), and C0.025 (14.18 mm) showed higher mean values at 0 s when compared to 20 s (12.67, 12.77 and 13.05 mm, respectivelly). Polymerization occurred within 40 s of light exposure for C0, C0.01, C0.025, and C0.05 and within 60 s for C0.1. In conclusion, the BHT concentrations had no significant influence on FS, FM and KH. The higher the BHT concentration, the longer was its handling time under light, with a significant improvement in the HR, but a decrease in DC. Therefore, BHT at 0.1% showed the best outcomes concerning all the BHT concentrations tested.

Resumo O objetivo foi investigar o efeito do inibidor de polimerização BHT no grau de conversão (GC), resistência à flexão (RF), módulo de flexão (MF), microdureza Knoop (KH) e redução da microdureza (RKH), e consistência de um compósito experimental contendo diferentes concentrações de BHT (% em peso): C0 - controle (0%); C0,01 (0,01%); C0,025 (0,025%); C0,05 (0,05%); C0,1 (0,1%); e C0,5 (0,5%). Para o teste de consistência, os compósitos foram testados imediatamente após serem expostos à luz de um refletor odontológico por 0, 20, 40 e 60 s. Os dados relativos a GC, RF, MF, KH e RKH foram submetidos a one-way ANOVA, enquanto os dados de consistência foram submetidos a two-way ANOVA; os valores médios foram comparados (teste de Tukey; α = 0,05). As análises de KH, RF e MF não mostraram diferença significativa entre os compósitos testados. Para GC, C0 apresentou o maior valor médio e diferiu apenas de C0,5. Para a RKH, C0,5 apresentou o menor valor médio e diferiu de C0 e C0,01. A análise de consistência não mostrou diferença entre C0,05, C0,1 e C0,5, considerando-se 0 e 20 s de exposição à luz, enquanto C0, C0,01 e C0,025 apresentaram maiores valores médios a 0 s quando comparados a 20 s. A polimerização ocorreu dentro de 40 s de exposição à luz para C0, C0.01, C0.025 e C0.05 e dentro de 60 s para C0.1. Em conclusão, as concentrações de BHT não tiveram influência significativa sobre RF, MF e KH. Quanto maior a concentração de BHT, maior o tempo de manuseio sob luz, com melhora significativa da RKH, mas diminuição da GC. Portanto, o compósito contendo 0,1 % de BHT apresentou os melhores resultados entre as demais concentrações testadas.

Mechanical performance of original; yellowish and blueish ProFile instruments: isolating heat-treatment as a variable

Resumo O presente estudo teve como objetivo realizar dois tratamentos térmicos diferentes em instrumentos de NiTi austenítico ProFile e comparar o desempenho mecânico de instrumentos originais e tratados termicamente. O tratamento térmico dos instrumentos ProFile (tamanho de ponta 25 e conicidade 0.06) foi realizado em um forno em atmosfera de argônio usando uma taxa de aquecimento de 10°C/min. Após atingir as temperaturas programadas de 450 ºC ou 500 ºC o sistema permaneceu em temperatura constante por 10 minutos; seguido de resfriamento em água à temperatura ambiente. Em seguida; os três grupos de instrumentos (n=30 por grupo) foram comparados quanto à fadiga cíclica (n=10 por grupo); flexão (n=10 por grupo) e resistência à flambagem (n=10 por grupo). Após testes de fadiga cíclica; um microscópio eletrônico de varredura foi utilizado para analisar as superfícies de fratura e observar o modo de fratura. A análise estatística foi realizada por meio dos testes de One-way ANOVA e teste de Student-Newman-Keuls; com erro de tipo alfa fixado em 0.05. Coloração amarelada e azulada foi observada nos instrumentos ProFile após tratamentos térmicos a 450 ºC ou 500 ºC; respectivamente. Os instrumentos ProFile originais apresentaram menor fadiga cíclica e maior resistência à flexão e flambagem (P<0.05). Em contraste; os instrumentos ProFile azulados (tratados termicamente a 500°C) apresentaram maior fadiga cíclica e menor resistência à flexão e flambagem (P>0.05). Pode-se concluir que os diferentes tratamentos térmicos realizados nos instrumentos ProFile aumentaram sua resistência à fadiga cíclica e melhoraram a flexibilidade e resistência à flambagem.

Abstract The present study aimed to perform two different heat-treatments in an austenitic NiTi ProFile instrument and to compare the mechanical performance of original and heat-treated instruments. Heat treatment of ProFile (tip size 25 and 0.06 taper) instruments were carried out in a furnace in argon atmosphere using a heating rate of 10° C/min. After reaching the programmed temperatures of 450 ºC or 500 ºC the system remained at a constant temperature for 10 minutes; followed by cooling in water at room temperature. Afterwards; the three groups (n=30 per group) of instruments were compared regarding their cyclic fatigue (n=10 per group); bending (n=10 per group); and buckling resistance (n=10 per group). After cyclic fatigue tests; a scanning electron microscope was used to analyze the fracture surfaces and observe the fracture mode. Statistical analysis was performed using One-way ANOVA and Student-Newman-Keuls test; with an alpha type error set at 0.05. Yellowish and blueish coloration was observed in the ProFile instruments after 450 ºC or 500 ºC heat treatments; respectively. Conventional ProFile instruments showed the lower cyclic fatigue; and the higher bending and buckling resistance (P<0.05). In contrast; yellowish ProFile instruments (heat treated at 500° C) showed the higher cyclic fatigue; and the lower bending and buckling resistance (P>0.05). It can be concluded that the different heat treatments performed on ProFile instruments increased its cyclic fatigue resistance and improved the flexibility and buckling resistance.

Desempeño Mecánico de Compuestos de Madera Plástica de Matriz Poliolefínica / Mechanical performance of polyolefinic wood plastic composites / Desempenho mecânicos de compostos de Madeira Plástica de Matriz Poliolefina

Resumen Los polímeros termoplásticos, pueden ser mezclados con diferentes tipos de cargas con el propósito de mejorar su rendimiento físico-mecánico, al mismo tiempo que permiten en muchos casos, generar soluciones a problemáticas ambientales como por ejemplo la disposición final de residuos de madera. Los compuestos de madera plástica son productos elaborados mediante la incorporación de fibras o partículas de madera en la matriz polimérica, donde la interacción entre los dos materiales (nula o con acople) es clave para lograr un adecuado desempeño del producto final. En esta revisión se establecen las matrices poliméricas y los tipos de maderas empleadas comúnmente en la elaboración de productos de madera plástica, al mismo tiempo que se definen los tratamientos previos que deben ser realizados tanto en la madera como en el polímero con el propósito de mejorar la compatibilidad de los dos materiales, y de esta manera mejorar propiedades como la absorción de agua, la resistencia a la descomposición, a la intemperie y el desempeño mecánico. En cuanto a las propiedades mecánicas, al adicionar un contenido de madera en el polímero se modifica la rigidez del material polimérico y la resistencia en tensión, flexión e impacto; sin embargo, se establece que es clave el uso de agentes funcionalizantes para que el efecto de la incorporación de la madera en polímero sea positivo. Finalmente se estudian las nuevas tendencias en el uso de diferentes tipos de residuos y matrices poliméricas para la elaboración de maderas plásticas.

Abstract Polymeric materials, especially thermoplastics, can be mixed with different types of fillers to improve their physical-mechanical performance, at the same time they allow, in many cases, to generate solutions to environmental problems such as the final disposal of wood waste. The plastic wood composites are products made by incorporating wood fibers in the polymer matrix, where the interaction between the two materials is key to achieve an adequate performance of the final product. This review establishes the polymer matrices and the types of wood commonly used in the production of plastic wood products, at the same time defining the previous treatments that must be carried out in the wood and in the polymer to improve the compatibility of the two materials, and in this way improve properties such as water absorption, resistance to decomposition, resistance to weathering and mechanical performance. Related to the mechanical properties, adding the wood fibers in the polymer modifies the rigidity of the polymeric material and the resistance in tension, bending and impact; however, it is established that the use of functionalizing agents is a fundamental key to improve the effect of wood incorporation into the polymer matrix. Finally, the new trends in the use of different types of waste and polymeric matrices to produce plastic wood are studied.

Resumo Os materiais poliméricos, principalmente os termoplásticos, podem ser misturados a diferentes tipos de cargas para melhorar seu desempenho físico-mecânico, ao mesmo tempo que, em muitos casos, permitem gerar soluções para problemas ambientais como a destinação final de resíduos. madeira. Os compósitos madeira-plástico são produtos obtidos pela incorporação de fibras de madeira à matriz polimérica, onde a interação entre os dois materiais é fundamental para um desempenho adequado do produto final. Nesta revisão, são estabelecidas as matrizes poliméricas e os tipos de madeira comumente utilizados na produção de produtos plásticos de madeira, ao mesmo tempo em que são definidos os tratamentos anteriores que devem ser realizados na madeira e no polímero para melhorar a compatibilidade dos dois materiais, e desta forma melhorar propriedades como absorção de água, resistência à decomposição, intempéries e desempenho mecânico. Em relação às propriedades mecânicas, ao adicionar as fibras de madeira ao polímero, a rigidez do material polimérico e a resistência à tração, flexão e impacto são modificadas; porém, está estabelecido que o uso de agentes funcionalizantes é fundamental para que o efeito da incorporação da madeira no polímero seja positivo. Por fim, são estudadas as novas tendências no uso de diferentes tipos de resíduos e matrizes poliméricas para a produção de madeira plástica.

Cytotoxicity and mechanical properties of the prosthetic liner / 中国康复理论与实践

@# Objective To investigate the current status of cytotoxicity and mechanical properties of the prosthetic liner on the market in China.Methods Six kinds of liner were collected, namely domestic 6 mm thick foam liner (A), domestic 5 mm thick EVA foam liner (B), German 5 mm thick EVA foam liner (C), Germany 12 mm thick PE foam liner (D), Iceland 3 mm thick silicone liner (E) and Germany 4 mm thick gel liner (F). Microscopic observation and thiazole blue colorimetry were used to detect the cytotoxicity. The content of small organic molecules was determined by the consumption of potassium permanganate. The tensile strength, elongation at break (%), and 100% tensile strength of the prosthetic liner were tested by material mechanics testing machine. The hardness was tested using the Shore hardness tester oo type.Results The cytotoxicity was grade 2 for prosthetic liners A, B, C and D, and was grade 0 for E and F. The redox substance content of prosthetic liners A、B、C exceeded 150 mg/kg. Except the prosthetic liner C, the hardness of the other products were all ≤ 70 HA. Except prosthetic liner D, the tensile strengths were > 1 MPa, breaking elongations were > 120.0%, 100% tensile strengths were > 0.9 MPa for other products.Conclusion Due to materials and production processes, the cytotoxicity and mechanical properties of the six samples are quite different.

Experimental Study on Puncture Mechanical Properties of Biomimetic Materials / 医用生物力学

Objective To obtain a more suitable puncture method for venipuncture robot through experiments.Methods By using different puncture speeds and angles for biomimetic materials, the force-time curves by various puncture methods were obtained. Results During puncture process, with the increase of the puncture angle, a smaller puncture force was required. The faster puncture speed would lead to a larger puncture force. Conclusions The 40°-45° puncture angleand the 120-300 mm/min puncture speed should be used for designing the puncture method of venipuncture robot. The results provide references for selecting the puncture angle and speed of the venipuncture robot.

Spatial Distribution of Biomechanical Characteristics for Trabecular Bone in the Femoral Head with Osteonecrosis / 医用生物力学

Objective To explore the spatial distribution of microstructural parameters and mechanical properties for trabecular bone in the femoral head with osteonecrosis. Methods Microstructural parameters and mechanical properties of trabecular bone in different regions were analyzed by combined use of imaging measurements and numerical simulation method, and the spatial distribution of biomechanical properties for trabecular bone along coronal, sagittal and vertical directions was investigated. Results Microstructural characteristics and mechanical properties of trabecular bone were Y-shaped distributed along coronal and sagittal directions, and mechanical properties of trabecular bone in Y-shaped region were higher than those in the other regions. Such distribution characteristics was consistent with the location of principle compressive group in the femoral head. Conclusions Necrotic lesions in Y-shaped region had a greater influence on stress distribution of the femoral head and might cause the deterioration of osteonecrosis. The spacial correlation between necrotic lesions and Y-shaped region should be fully considered during clinical diagnosis.

Research progress in influencing factors on mechanical properties of medical PVC / 国际生物医学工程杂志

PVC resin is widely used in medical and other industrial fields because of its good chemical corrosion resistance, wear resistance, low cost and simple production. In this study, the related research progress in the influence of resin polymerization degree, processing technology and processing aids on the mechanical properties of PVC was reviewed, and the influence rules of processing aids on the properties of PVC was analyzed. Relevant research results show that the increase of the resin polymerization degree can increase the strength of PVC, but at the same time reduce the toughness. The use of compression molding process is beneficial to improve the strength and modulus of PVC. The use of injection molding process is beneficial to improve the plasticity and toughness of the PVC. Properly increasing the processing temperature and the blending time can improve the toughness of PVC. Adding heat stabilizers can improve the plasticity, toughness and strength of PVC. Adding plasticizers can improve the strength and toughness of PVC. Adding modifiers can improve the strength and toughness of PVC.

Mechanical Model for Evaluating Curative Effect of Laser on Hypertrophic Scar / 医用生物力学

:Objective To establish a mechanical model with times of laser treatment as the independent variable in treatment process of rabbit ear hypertrophic scar (HPS) by combining experimental research and numerical simulation, so as to evaluate the curative effect of HPS. Methods Firstly, the HPS model of rabbit ear was established by CO2 laser instrument, and then the HPS was treated for continuous three times by pulsed dye laser (PDL) combined with CO2 lattice laser. After each treatment, the uniaxial compressive mechanical properties of HPS were tested to fit Ogden hyperelastic model to obtain mechanical parameters of HPS during the treatment. The functional relationship between mechanical parameters of HPS and times of laser treatment was established by LM optimization algorithm. Results Mechanical parameters of HPS increased with the increase of laser treatment times, and gradually became a constant, namely, mechanical parameters of normal skin. With the increase of laser treatment times, the growth ratio of HPS mechanical parameters gradually decreased. The initial growth ratio was 60% and decreased to 4.09% after three times of treatment. Conclusions The initial curative effect of laser therapy is the most obvious, and with the relief of symptoms, the effect of single laser therapy is no longer significant.

Study on Anisotropy Properties of in vitro Pig Trachea and Numerical Simulation / 医用生物力学

Objective To study mechanical properties of the anisotropy for pig trachea and main bronchi, and determine the constitutive model of trachea deformation by finite element numerical simulation. Methods The pig tracheas were collected and cut through in their axial directions and expanded into two-dimensional planes. Then, by setting the length direction of the trachea aortas as 0°, each planar trachea was anticlockwisely cut into 6 samples with orientation of 30°,60°,90°,120°,150° and 180°, respectively. Uniaxial tensile tests were applied on the specimen in 6 angular directions by using the electronic universal test machine, to obtain stress and strain of the specimen in different directions. Nonlinear fitting to the experimental data was performed by using the Mooney-Rivilin hyperelastic model, in order to obtain the material characteristic parameters. Finite element models of the trachea and the main bronchi were established, and tensile numerical simulation was carried out.Results Samples at different angles showed different stress-strain curves. In the trachea, the stresses of samples with angle of 30°, 120° and 150° were in the range of 1.0-1.5 MPa, the stresses of samples with angle of 60° and 90° were in the range of 0.5-1.0 MPa, and the stresses of samples with angle of 180° were in the range of 2.5-3.0 MPa. In the main bronchi, the stresses of samples with angle of 30°, 120° and 150° were in the range of 0.8-1.0 MPa, the stresses of samples with angle of 90° and 180° were in the range of 1.4-1.8 MPa, and the stresses of samples with angle of 120° were in the range of 0.4-0.6 MPa. There was an obvious difference between the trachea and the main bronchi. The finite element simulation verified that the Mooney-Rivilin constitutive model was suitable for describing small deformation behavior of the trachea. Conclusions The pig trachea exhibits strong anisotropy. Meanwhile, the Mooney-Rivilin model can characterize small tracheal deformations. The results provide theoretical references for tracheal resection and reconstruction in clinical treatment and intervention with surgical instruments such as bronchoscopy.

Effects of storage duration on compressive mechanical properties of rabbit patellar ligament / 医用生物力学

Objective To study the effect of storage duration on compressive mechanical properties of rabbit patellar, so as to provide references for in vitro ligament storage.Methods The compressive mechanical properties of rabbit patellar ligament storaged at -20 ℃ at different storage durations (in 36 d) were tested with the universal tensile test machine. The microscopic morphology of collagen fibers was observed under the scanning electron microscopy (SEM). The enthalpy and denaturation temperature of collagen fibers were measured with differential scanning calorimetry (DSC).Results With the increase of storage duration, the compressive stress of the patellar ligament at 40% strain increased from 19 kPa to 112 kPa and then decreased to 57 kPa. SEM observation showed that the cross-linking of collagen fibers was initially strengthened and then weakened. DSC results showed that the enthalpy increased from 59.47 J/g to 67.10 J/g and then decreased to 54.43 J/g. The denaturation temperature increased from 67.62 ℃ to 77.28 ℃ and then decreased to 64.10 ℃.Conclusions When rabbit patellar ligament is stored at -20 ℃, with the increase of storage duration, the compressive stress of rabbit patellar ligament at 40% strain increases at first and then decreases. This change may be due to the variation of cross-linking level of collagen fibers. The stronger the cross-linking of collagen fibers, the stronger the compressive mechanical properties will be.

Post-cure heat treatments influence on mechanical and optical properties of resin composites

Abstract This study evaluated the effect of post-cure heat treatment (PCHT) on the Knoop microhardness (KHN), degree of conversion (DC), color changes, and contrast ratio (CR) of four resin composites (RCs): Z100 (3M ESPE), Z350 XT (3M ESPE), Estelite Omega (Tokuyama) and Empress Direct (Ivoclar Vivadent). Specimens (12 × 1 mm) were prepared for each material (n = 10 / group). After curing, samples were subjected to PCHT for 10 min at 100°C or 170°C. Control group was maintained at room temperature (24°C) for the same time. The DC was analyzed by FT-NIR immediately and 24 h after the PCHT (n = 3 / group). KHN was analyzed 24 h after PCHT (n = 10 / group). According to CIEDE2000 (∆E00), color measurements were obtained immediately after curing, five minutes after PCHT, and after seven days of storage in water, coffee, and red wine. Data were analyzed by One and Two-Way ANOVA (p < 0.05). Z100, Z350, and Estelite Omega showed increases in KHN with increased temperature (p < 0.05). PCHT at 100°C and 170°C led to a higher DC of all RCs (p < 0.05). Initially, the PCHT lead to increased ∆E00 values (p < 0.05), which was decreased after immersion in coffee and wine (p < 0.05). Considering the effect of PCHT and staining solutions, lower color changes were observed in the thermally treated specimens (p < 0.05). Taken collectively, the results suggest the PCHT as an economical and practical alternative to enhance direct RC's properties in direct-indirect and indirect restorations.

Resumo Este estudo avaliou o efeito do tratamento térmico pós-cura (PCHT) na microdureza Knoop (KHN), grau de conversão (DC), mudanças de cor e razão de contraste (CR) de quatro compósitos resinosos (RCs): Z100 (3M ESPE ), Z350 XT (3M ESPE), Estelite Omega (Tokuyama) e Empress Direct (Ivoclar Vivadent). Corpos de prova (12 × 1 mm) foram preparadas para cada material (n = 10 / grupo). Após a cura, as amostras foram submetidas ao PCHT por 10 min a 100 ou 170° C. O grupo controle foi mantido à temperatura ambiente (24° C) pelo mesmo tempo. O DC foi analisada por FT-NIR imediatamente e 24 h após a PCHT (n = 3 / grupo). KHN foi analisado 24 h após PCHT (n = 10 / grupo). De acordo com o CIEDE2000 (∆E00), as medidas de cor foram obtidas imediatamente após a cura, cinco minutos após a PCHT e após sete dias de armazenamento em água, café e vinho tinto. Os dados foram analisados por ANOVA de um e dois fatores (P < 0,05). Z100, Z350 XT e Estelite Omega mostraram aumentos no KHN com o aumento da temperatura (P < 0,05). PCHT a 100 ° C e 170 ° C levou a uma maior DC de todos os RCs (P < 0,05). Inicialmente, o PCHT levou ao aumento dos valores de ∆E00 (P < 0,05), que diminuiu após a imersão em café e vinho (P < 0,05). Considerando o efeito de PCHT e soluções de coloração, menores mudanças de cor foram observadas nas amostras tratadas termicamente (P < 0,05). Os resultados sugerem o PCHT como uma alternativa econômica e prática para aumentar as propriedades diretas de compósitos resinosos em restaurações diretas-indiretas e indiretas.

CHX stabilizes the resin/demineralized dentin interface

Abstract The aim of this study was to evaluate the effect of 2% chlorhexidine digluconate (CHX) on microtensile bond strength (µTBS) between an adhesive system and under 3 dentin conditions. For that, this study evaluated the adhesive interface at initial, after 6 months and 1 year of storage. Forty-eight human third molars were prepared and randomly divided into 3 groups, according to dentin substrates: sound dentin (Sd), caries-infected dentin (Ci) and caries-affected dentin (Ca). The groups were subdivided into two according to the dentin pre-treatment: application of 2% CHX or without pre-treatment (control). The dentin surfaces were etched with 35% phosphoric acid gel and bonded with Adper Single Bond 2 (3M ESPE) adhesive system according to manufacturer's instructions. Subsequently, the specimens were stored in deionized water at 37°C for 24h, 6 months and 1 year. Two additional teeth were used to analyze the bonding interfaces by SEM. Data was submitted to three-way ANOVA in a split plot design and Tukey's test (α = 0.05). The results showed that Ci decreased µTBS values when compared to Ca and Sd, regardless storages time or treatment. Stored samples for 6 months and 1 year decreased the µTBS for the control group, but no difference was found between storages time for the CHX group. As a conclusion, the 2% CHX application after etching showed improved dentin bond strength in the storage time, regardless of the substrates evaluated.

Resumo O objetivo deste estudo foi avaliar o efeito do digluconato de clorexidina 2% (CHX) na resistência de união à microtração (µTBS) entre um sistema adesivo e sob 3 condições de dentina. Para tanto, este estudo avaliou a interface adesiva no início, após 6 meses e 1 ano de armazenamento. Quarenta e oito terceiros molares humanos foram preparados e divididos aleatoriamente em 3 grupos, de acordo com os substratos dentinários: dentina hígida (Dh), dentina infectada por cárie (Di) e dentina afetada por cárie (Da). Os grupos foram subdivididos em dois de acordo com o pré-tratamento: aplicação de CHX 2% ou sem pré-tratamento (controle). As superfícies da dentina foram condicionadas com gel de ácido fosfórico a 35%, em seguida, utilizou-se o sistema adesivo Adper Single Bond 2 (3M ESPE) de acordo com as instruções do fabricante. Posteriormente, os corpos-de-prova foram armazenados em água deionizada a 37°C por 24h, 6 meses e 1 ano. Dois dentes adicionais foram usados ​​para analisar as interfaces de união no MEV. Os dados foram submetidos a ANOVA três fatores em esquema de parcela subdividida e ao teste de Tukey (α = 0,05). Os resultados mostram que a Di diminuiu os valores de µTBS quando comparado as Da e Dh, independente do tempo de armazenamento ou tratamento. Amostras armazenadas por 6 meses e 1 ano diminuíram a µTBS para o grupo de controle, mas nenhuma diferença foi encontrada entre o tempo de armazenamento para o grupo CHX. A aplicação de CHX 2% após o condicionamento apresentou melhora na resistência de união à dentina no tempo de armazenamento, independente dos substratos avaliados.

Mechanical Properties of Teeth Restored After Selective Caries Excavation. Systematic Review and Meta-Analysis

ABSTRACT: The aim of this study was to systematically review the literature of in vitro studies comparing the mechanical properties of teeth restored after selective caries excavation (SCE) and complete caries excavation (CCE). The PubMed/MEDLINE and EMBASE electronic databases were searched systematically. In vitro studies investigating the mechanical properties of teeth restored after SCE, were independently checked by two authors. Inclusion criteria were: (1) performing SCE (2) mentioning the teeth were later restored, and (3) evaluating mechanical properties of the restored teeth. Meta-analysis was performed with and without discriminating between shallow and deep lesions. From 1,859 potentially eligible studies, 14 were selected for full text analysis and 5 were included in the meta- analysis. Fracture resistance was significantly lower after SCE than after CCE in overall analysis (SMD[95%CI]=-1.62[-3.04,-0.20]) and for deep lesion (SMD[95%CI]=-1.62[-2.62,-0.61]), whereas cuspal deflection at 200 and 400N was significantly higher after SCE than after CCE for discriminated and non- discriminated analyses. Furthermore, for shallow lesions the risk of catastrophic fracture was significantly lower after SCE than CCE (RR[95%CI]=0.58[0.43,0.78]). The included studies presented low and medium risk of bias. The mechanical behavior of restored teeth seems to be affected by the excavation strategy. Although there is a tendency for lower fracture resistance and higher cuspal deflection after SCE, there is a lower risk of catastrophic failure when compared to CCE. However, this conclusion is based on very few in vitro studies.

RESUMEN: El objetivo de este estudio fue revisar sistemáticamente la literatura de estudios in vitro que comparan las propiedades mecánicas de los dientes restaurados después de la excavación selectiva de caries (ESC) y la excavación de caries completa (ECC). Se realizaron búsquedas sistemáticas en las bases de datos electrónicas PubMed / MEDLINE y EMBASE. Los estudios in vitro que investigan las propiedades mecánicas de los dientes restaurados después de la ESC fueron verificados de forma independiente por dos autores. Los criterios de inclusión fueron: (1) realizar ESC (2) mencionar que los dientes fueron posteriormente restaurados y (3) evaluar las propiedades mecánicas de los dientes restaurados. El metanálisis se realizó con y sin discriminación entre lesiones superficiales y profundas. De 1.859 estudios potencialmente elegibles, se seleccionaron 14 para el análisis de texto completo y 5 se incluyeron en el metanálisis. La resistencia a la fractura fue significativamente menor después de ESC que después de CCE en el análisis general (DME [IC del 95 %] = - 1,62 [-3,04, -0,20]) y para la lesión profunda (DME [IC del 95 %] = - 1,62 [-2,62, - 0,61]), mientras que la deflexión de las cúspides a 200 y 400 N fue significativamente mayor después de ESC que después de CCE para análisis discriminados y no discriminados. Además, para las lesiones superficiales, el riesgo de fractura catastrófica fue significativamente menor después de ESC que de CCE (RR [IC 95 %] = 0,58 [0,43,0,78]). Los estudios incluidos presentaron riesgo de sesgo bajo y medio. El comportamiento mecánico de los dientes restaurados parece verse afectado por la estrategia de excavación. Aunque existe una tendencia a una menor resistencia a la fractura y una mayor deflexión de la cúspide después de la ESC, existe un menor riesgo de falla catastrófica en comparación con la CCE. Sin embargo, esta conclusión se basa en muy pocos estudios in vitro.

Avaliação das propriedades físico-químicas de instrumentos reciprocantes de níquel-titânio tratados termicamente / Evaluation of the physicochemical properties of heat-treated nickel-titanium reciprocating instruments

Os instrumentos endodônticos de níquel-titânio acionados a motor foram desenvolvidos para se obter um preparo químico-mecânico mais rápido e seguro, no entanto, esses instrumentos apresentam como desvantagem o risco de fraturar durante o seu uso. Diante disso, os fabricantes têm desenvolvido mudanças no design dos instrumentos, nos acabamentos das ligas e na cinemática de uso, pois são características que contribuem para que as fraturas aconteçam. O objetivo deste estudo foi avaliar e comparar propriedades mecânicas de novos instrumentos de níquel-titânio com memória controlada lançados no mercado. Os sistemas WaveOne Gold (WOG; Dentsply Sirona, Ballaigues, Switzerland), WA1 File (WA1; TDKaFile, Cidade do México, México) e X1 File (X1; MK Life, Porto Alegre, RS, Brasil) foram submetidos ao teste de resistência à torção, de acordo com a norma ISO 3630-1, ao teste rigidez à flexão, através do ensaio de flexão em cantiléver (45º) e ao teste de resistência à flambagem. Os resultados foram avaliados através da análise de variância (ANOVA), o teste F e o teste de Tukey, considerando um nível de significância de 5%. No teste de resistência à torção os instrumentos WOG apresentaram maior deflexão angular, ou seja, maior resistência à fratura em torção, enquanto os instrumentos WA1 a menor e na comparação do torque máximo em torção não houve diferença estatística significante entre os sistemas. Nos testes de rigidez a flexão e resistência à flambagem houve diferença estatística significante entre os 3 sistemas, sendo os instrumentos X1 os mais rígidos. No primeiro teste os instrumentos WA1 se apresentaram como os mais flexíveis e no segundo, os instrumentos WOG. Conclui-se que os instrumentos WOG, WA1 e X1 mostraram diferenças estatísticas nos testes mecânicos, sendo os instrumentos WOG e WA1 os mais resistentes à fratura por torção e os mais flexíveis, diferentemente dos instrumentos X1 que se apresentaram mais susceptíveis à fratura por torção e menos flexíveis (AU)

Reciprocating nickel-titanium endodontic instruments have been developed to obtain a faster and safer preparation, however, these instruments have the disadvantage of fracturing during use. Facing this disadvantage, manufacturers have developed changes in instrument design and alloy finishes, as metallurgical characteristics are one of the factors that contribute to fractures. The aim of this study was to evaluate and compare mechanical properties of new nickel-titanium instruments with controlled memory. The WaveOne Gold (WOG; Dentsply Sirona, Ballaigues, Switzerland), WA1 File (WA1; TDKaFile, Mexico City, Mexico) and X1 File (X1; MK Life, Porto Alegre, RS, Brazil) systems were subjected to the torsional fatigue test, according to the ISO 3630-1 standard, flexural stiffness test, through the cantilever flexion test (45°) and buckling resistance test. The results were evaluated through analysis of variance (ANOVA), the F test and the Tukey test, considering a significance level of 5%. In the torsional fatigue test, the WOG instruments showed greater angular deflection, that is, greater resistance to torsional fracture and the WA1 instruments the lesser, and when comparing the maximum torsional torque, there was no statistically significant difference between the systems. In the flexural stiffness and buckling resistance tests, there was a statistically significant difference between the 3 systems, with the X1 instruments being the most rigid. In the first test, the WA1 instruments were the most flexible followed by the WOG instruments. In conclusion, the WOG, WA1 and X1 instruments showed differences in the mechanical tests, with the WOG and WA1 instruments being the most resistant to torsion fracture and the most flexible, unlike the X1 instruments that were more susceptible to torsion fracture and also the most rigid (AU).