Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 67.889
Filtrar
1.
ACS Appl Mater Interfaces ; 13(27): 31379-31392, 2021 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-34197081

RESUMO

Osteoarthritis (OA) is treated with the intra-articular injection of steroids such as dexamethasone (DEX) to provide short-term pain management. However, DEX treatment suffers from rapid joint clearance. Here, 20 × 10 µm, shape-defined poly(d,l-lactide-co-glycolide)acid microPlates (µPLs) are created and intra-articularly deposited for the sustained release of DEX. Under confined conditions, DEX release is projected to persist for several months, with only ∼20% released in the first month. In a highly rigorous murine knee overload injury model (post-traumatic osteoarthritis), a single intra-articular injection of Cy5-µPLs is detected in the cartilage surface, infrapatellar fat pad/synovium, joint capsule, and posterior joint space up to 30 days. One intra-articular injection of DEX-µPL (1 mg kg-1) decreased the expression of interleukin (IL)-1ß, tumor necrosis factor (TNF)-α, IL-6, and matrix metalloproteinase (MMP)-13 by approximately half compared to free DEX at 4 weeks post-treatment. DEX-µPL also reduced load-induced histological changes in the articular cartilage and synovial tissues relative to saline or free DEX. In sum, the µPLs provide sustained drug release along with the capability to precisely control particle geometry and mechanical properties, yielding long-lasting benefits in overload-induced OA. This work motivates further study and development of particles that provide combined pharmacological and mechanical benefits.


Assuntos
Cartilagem Articular/metabolismo , Dexametasona/química , Dexametasona/metabolismo , Portadores de Fármacos/química , Osteoartrite/tratamento farmacológico , Osteoartrite/metabolismo , Animais , Biomarcadores/metabolismo , Preparações de Ação Retardada , Dexametasona/administração & dosagem , Dexametasona/uso terapêutico , Regulação da Expressão Gênica/efeitos dos fármacos , Injeções Intra-Articulares , Camundongos , Copolímero de Ácido Poliláctico e Ácido Poliglicólico/química , Estresse Mecânico
2.
Int J Mol Sci ; 22(11)2021 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-34199865

RESUMO

In obese patients, enhanced serum levels of free fatty acids (FFA), such as palmitate (PA) or oleate (OA), are associated with an increase in systemic inflammatory markers. Bacterial infection during periodontal disease also promotes local and systemic low-grade inflammation. How both conditions concomitantly impact tooth movement is largely unknown. Thus, the aim of this study was to address the changes in cytokine expression and the secretion of human periodontal ligament fibroblasts (HPdLF) due to hyperlipidemic conditions, when additionally stressed by bacterial and mechanical stimuli. To investigate the impact of obesity-related hyperlipidemic FFA levels on HPdLF, cells were treated with 200 µM PA or OA prior to the application of 2 g/cm2 compressive force. To further determine the additive impact of bacterial infection, HPdLF were stimulated with lipopolysaccharides (LPS) obtained from Porphyromonas gingivalis. In mechanically compressed HPdLF, PA enhanced COX2 expression and PGE2 secretion. When mechanically stressed HPdLF were additionally stimulated with LPS, the PGE2 and IL6 secretion, as well as monocyte adhesion, were further increased in PA-treated cultures. Our data emphasize that a hyperlipidemic condition enhances the susceptibility of HPdLF to an excessive inflammatory response to compressive forces, when cells are concomitantly exposed to bacterial components.


Assuntos
Fibroblastos/imunologia , Hiperlipidemias/fisiopatologia , Inflamação/imunologia , Lipopolissacarídeos/farmacologia , Ligamento Periodontal/imunologia , Porphyromonas gingivalis/química , Estresse Mecânico , Força Compressiva , Citocinas/metabolismo , Fibroblastos/efeitos dos fármacos , Fibroblastos/patologia , Humanos , Inflamação/induzido quimicamente , Inflamação/patologia , Ligamento Periodontal/efeitos dos fármacos , Ligamento Periodontal/patologia , Pressão
3.
Int J Mol Sci ; 22(13)2021 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-34206862

RESUMO

We report an ultra-high vacuum low-temperature scanning tunneling microscopy (STM) study of the C60 monolayer grown on Cd(0001). Individual C60 molecules adsorbed on Cd(0001) may exhibit a bright or dim contrast in STM images. When deposited at low temperatures close to 100 K, C60 thin films present a curved structure to release strain due to dominant molecule-substrate interactions. Moreover, edge dislocation appears when two different wavy structures encounter each other, which has seldomly been observed in molecular self-assembly. When growth temperature rose, we found two forms of symmetric kagome lattice superstructures, 2 × 2 and 4 × 4, at room temperature (RT) and 310 K, respectively. The results provide new insight into the growth behavior of C60 films.


Assuntos
Microscopia de Tunelamento/métodos , Compostos Organometálicos/química , Cristalização , Polimerização , Estresse Mecânico , Temperatura , Vácuo
4.
Int J Mol Sci ; 22(11)2021 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-34205045

RESUMO

SGLT-2i's exert direct anti-inflammatory and anti-oxidative effects on resting endothelial cells. However, endothelial cells are constantly exposed to mechanical forces such as cyclic stretch. Enhanced stretch increases the production of reactive oxygen species (ROS) and thereby impairs endothelial barrier function. We hypothesized that the SGLT-2i's empagliflozin (EMPA), dapagliflozin (DAPA) and canagliflozin (CANA) exert an anti-oxidative effect and alleviate cyclic stretch-induced endothelial permeability in human coronary artery endothelial cells (HCAECs). HCAECs were pre-incubated with one of the SGLT-2i's (1 µM EMPA, 1 µM DAPA and 3 µM CANA) for 2 h, followed by 10% stretch for 24 h. HCAECs exposed to 5% stretch were considered as control. Involvement of ROS was measured using N-acetyl-l-cysteine (NAC). The sodium-hydrogen exchanger 1 (NHE1) and NADPH oxidases (NOXs) were inhibited by cariporide, or GKT136901, respectively. Cell permeability and ROS were investigated by fluorescence intensity imaging. Cell permeability and ROS production were increased by 10% stretch; EMPA, DAPA and CANA decreased this effect significantly. Cariporide and GKT136901 inhibited stretch-induced ROS production but neither of them further reduced ROS production when combined with EMPA. SGLT-2i's improve the barrier dysfunction of HCAECs under enhanced stretch and this effect might be mediated through scavenging of ROS. Anti-oxidative effect of SGLT-2i's might be partially mediated by inhibition of NHE1 and NOXs.


Assuntos
Células Endoteliais/efeitos dos fármacos , Inflamação/tratamento farmacológico , Estresse Oxidativo/efeitos dos fármacos , Proteínas de Transporte de Sódio-Glucose/antagonistas & inibidores , Trocador 1 de Sódio-Hidrogênio/antagonistas & inibidores , Compostos Benzidrílicos/farmacologia , Canagliflozina/farmacologia , Permeabilidade da Membrana Celular/efeitos dos fármacos , Células Endoteliais/metabolismo , Glucosídeos/farmacologia , Guanidinas/farmacologia , Humanos , Inflamação/genética , Inflamação/patologia , NADPH Oxidases/antagonistas & inibidores , NADPH Oxidases/genética , Estresse Oxidativo/genética , Pirazóis/farmacologia , Piridonas/farmacologia , Espécies Reativas de Oxigênio/metabolismo , Proteínas de Transporte de Sódio-Glucose/genética , Inibidores do Transportador 2 de Sódio-Glicose/farmacologia , Trocador 1 de Sódio-Hidrogênio/genética , Estresse Mecânico , Sulfonas/farmacologia
5.
J Contemp Dent Pract ; 22(4): 335-341, 2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-34266999

RESUMO

AIM AND OBJECTIVE: The aim and objective of this study is to evaluate the interface between heat-pressed glass-ceramic masses on a Cr-Co metal substrate using a scanning electron microscope and an X-ray energy dispersion spectrometer. MATERIALS AND METHODS: A pressed porcelain-leucite-based ceramic (IPS InLine press-on-metal (PoM); Ivoclar Vivadent AG) was used. Three cylindrical metal specimens cast (diameter 5 mm, height 1.5 mm) in Co-Cr alloy and covered with pressed ceramic (height 1.5 mm), according to the instructions of the manufacturer. All the specimens were covered with conductive carbon and then examined with a scanning electron microscope. The interface areas were studied using projections from an ETD secondary emission detector and a reversing atomic SSD contrast beam at a magnification of 1200× and 2000×, with a voltage 25 kV acceleration and 110 mA climb current. The elemental analysis was done with genesis 3.5 software, without the use of templates. Surface mapping areas and linear line scan projections of elemental distributions during the interface were recorded. RESULTS: The distribution of specific elements in the ceramic coating concludes the existence of ion diffusion from one side of the interface to the other, which leads to an initial conclusion of the development of primary bonds with oxygen bridges. Also, in the interface, there are ledges of the mass of opaquer on the metal substrate, which results in the creation of a mechanical bond. Therefore, the adhesive mechanism must be due to both micromechanical retention and wetting phenomena and is similar to the conventional layering technique. CONCLUSION: The PoM technique can be used as an alternative fabrication method for metal-ceramic restorations. Factors, such as material composition and properties, firing temperatures, cooling rates, operator's skill, porosities, and fabrication process, may affect the quality and strength of the bond between the core and the veneering materials. CLINICAL SIGNIFICANCE: The PoM technique can be used as an alternative fabrication method for metal-ceramic restorations.


Assuntos
Colagem Dentária , Ligas Metalo-Cerâmicas , Cerâmica , Porcelana Dentária , Temperatura Alta , Teste de Materiais , Microscopia Eletrônica de Varredura , Estresse Mecânico , Propriedades de Superfície
6.
J Contemp Dent Pract ; 22(4): 427-434, 2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-34267014

RESUMO

AIM: The aim of this systemic review is to investigate these parameters by analyzing the characteristics of fractured instruments to determine which is the most relevant mechanical stress that induces intracanal separation in vivo. BACKGROUND: The fracture of nickel-titanium (Ni-Ti) instruments is a result of flexural fatigue and torsional fatigue. An electronic search was conducted in MEDLINE database, Web of Science, and Cochrane following preferred reporting items for systematic reviews and meta-analyses guidelines. Data were collected and the key features from the included studies were extracted. Overview quality assessment questionnaire scoring assessed the quality of the articles. A total of 12 articles were selected, where the lowest score was 13. REVIEW RESULTS: Considering Ni-Ti rotary instruments, this overall evaluation comprehends 939 broken instruments with an incidence of fracture of 5%. Out of the 12 selected articles, 10 studies revealed that flexural failure was the predominant mode (range of 62-92%). It appears that motion plays an important role when it comes to mechanisms of fracture. The majority of defects found in hand-operated instruments were in the form of torsional failure. Although the major cause of separation of rotary instruments is flexural fatigue, smaller instruments show more torsional fracture than the larger instruments. The average fragment length was found to be 2.5 mm and 3.35 mm, respectively, for torsional failure and flexural failure. The risk of bias depends on fractographic analysis. CONCLUSION: Flexural fatigue is the predominant mode of fracture in rotary Ni-Ti instruments. The type of motion and size of the instrument seem to affect the mechanism of fracture. Fragment length may show a strong association with the type of fracture mechanism. CLINICAL SIGNIFICANCE: This systemic review found that flexural fatigue is the most relevant mechanical stress that induces intracanal separation in vivo. Moreover, in clinical practice, the fragment length might be an excellent indicator of the type of fracture.


Assuntos
Níquel , Titânio , Ligas Dentárias , Instrumentos Odontológicos , Desenho de Equipamento , Falha de Equipamento , Incidência , Preparo de Canal Radicular , Estresse Mecânico , Torção Mecânica
7.
Int J Mol Sci ; 22(12)2021 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-34207723

RESUMO

A hypofibrotic phenotype has been observed in cardiac fibroblasts (CFs) isolated from a volume overload heart failure model, aortocaval fistula (ACF). This paradoxical phenotype results in decreased ECM synthesis despite increased TGF-ß presence. Since ACF results in decreased tissue stiffness relative to control (sham) hearts, this study investigates whether the effects of substrate stiffness could account for the observed hypofibrotic phenotype in CFs isolated from ACF. CFs isolated from ACF and sham hearts were plated on polyacrylamide gels of a range of stiffness (2 kPa to 50 kPa). Markers related to cytoskeletal and fibrotic proteins were measured. Aspects of the hypofibrotic phenotype observed in ACF CFs were recapitulated by sham CFs on soft substrates. For instance, sham CFs on the softest gels compared to ACF CFs on the stiffest gels results in similar CTGF (0.80 vs. 0.76) and transgelin (0.44 vs. 0.57) mRNA expression. The changes due to stiffness may be explained by the observed decreased nuclear translocation of transcriptional regulators, MRTF-A and YAP. ACF CFs appear to have a mechanical memory of a softer environment, supported by a hypofibrotic phenotype overall compared to sham with less YAP detected in the nucleus, and less CTGF and transgelin on all stiffnesses.


Assuntos
Fibroblastos/metabolismo , Regulação da Expressão Gênica , Insuficiência Cardíaca/metabolismo , Miocárdio/metabolismo , Estresse Mecânico , Animais , Fibroblastos/patologia , Fibrose , Insuficiência Cardíaca/patologia , Masculino , Miocárdio/patologia , Ratos , Ratos Sprague-Dawley
8.
J Biol Regul Homeost Agents ; 35(3 Suppl. 1): 213-218, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34289681

RESUMO

The loss of dental substance due to the presence of decay, to wide conservative repairs, to the preparation of prosthetics or to enamel-dentine fractures, often causes an important structural weakening in the element that is endodontically treated (1-15). It is therefore necessary to use endocanal posts in the coronal reconstruction. Mineral fibre posts and epoxy resins that are available at present, fixed with resinous cements, thanks to their excellent integration, exceed the concept of reconstruction, meant as assembly of heterogeneous materials, arranging homogeneous materials according to a similar flexibility module (16-18). This allows to get a "post dentine cement monobloc", which is ideal for the morphofunctional tooth resetting (19-35). The aim of our experimental study was to analyse and compare the surface characteristics of same posts that are available at present by observing them in their relationship with cement and dental materials (36-44).


Assuntos
Cimentação , Técnica para Retentor Intrarradicular , Resinas Compostas , Vidro , Teste de Materiais , Estresse Mecânico , Propriedades de Superfície
9.
Zhonghua Shao Shang Za Zhi ; 37(7): 647-653, 2021 Jul 20.
Artigo em Chinês | MEDLINE | ID: mdl-34304405

RESUMO

Objective: To establish mechanical stress-induced hypertrophic scar mouse models, and to examine the roles of interleukin-6/signal transduction and activator of transcription 3 (IL-6/STAT3) pathway and ß-catenin. Methods: The experimental research method was used. Sixteen female C57/BL6 mice of 12-week-old were collected and two straight full-thickness skin incisions of 2 cm in length were inflicted on the back of each mouse. On the fourth day post injury, the two wounds on the back of each mouse were divided into mechanical traction group and blank control group according to the random number table method, with 16 wounds in each group. The wounds in mechanical traction group were given continuous mechanical traction for 14 days, while the wounds in blank control group were given no treatment. After 14 days of mechanical traction for wounds in mechanical traction group, the appearances of the scar tissue in wounds of 2 groups were visually observed, and the areas of scars were measured; the morphological changes of the scar tissue in wounds of 2 groups were observed by hematoxylin-eosin staining, and the cross-sectional areas of scars were measured; the content of IL-6 in supernatant of the scar tissue in wounds of 2 groups was detected by enzyme-linked immunosorbent assay; the protein expression of phosphorylated STAT3 (p-STAT3) of the scar tissue in wounds of 2 groups was detected by Western blotting; and the expression of ß-catenin of the scar tissue in wounds of 2 groups was detected by immunohistochemistry. Data were statistically analyzed with paired sample t test. Results: Red hairless area similar to human scar tissue formed in wounds of mechanical traction group after 14 days of mechanical traction, with large area of scar, thickened local area, hardened texture, and some even slightly raised, while scar in wounds of blank control group was linear and not obvious. After 14 days of mechanical traction for wounds in mechanical traction group, the scar area of wounds in mechanical traction group was (5.65±0.95) mm2, which was significantly larger than (1.07±0.28) mm2 in blank control group (t=26.333, P<0.01). After 14 days of mechanical traction for wounds in mechanical traction group, the skin appendages of scar tissue were absent, and the dermis hyperplasia was active and obviously thickened, while skin appendages of scar tissue of wounds in blank control group were still present, with unconspicuous dermis hyperplasia; the cross-sectional area of scar in wounds of mechanical traction group was (0.82±0.23) mm2, which was significantly larger than (0.29±0.07) mm2 of blank control group (t=8.879, P<0.01). After 14 days of mechanical traction for wounds in mechanical traction group, the content of IL-6 in the supernatant of scar tissue and the protein expression of p-STAT3 in scar tissue of wounds in mechanical traction group were significantly higher than those in blank control group (t=37.552, 25.863, P<0.01). The expression of ß-catenin was high in the scar tissue of wounds in mechanical traction group after 14 days of mechanical traction, while that in blank control group was low. Conclusions: The study successfully establishes mechanical stress-induced hypertrophic scar mouse models. Mechanical stress can participate in wound healing and induce scar hyperplasia of mice wounds through continuous or overexpression of IL-6/STAT3 pathway, and ß-catenin can also promote the formation of hypertrophic scar.


Assuntos
Cicatriz Hipertrófica , Animais , Feminino , Interleucina-6 , Camundongos , Transdução de Sinais , Estresse Mecânico , beta Catenina
10.
Sensors (Basel) ; 21(12)2021 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-34200918

RESUMO

This research employs displacement fields photogrammetrically captured on the surface of a solid or structure to estimate real-time stress distributions it undergoes during a given loading period. The displacement fields are determined based on a series of images taken from the solid surface while it experiences deformation. Image displacements are used to estimate the deformations in the plane of the beam surface, and Poisson's Method is subsequently applied to reconstruct these surfaces, at a given time, by extracting triangular meshes from the corresponding points clouds. With the aid of the measured displacement fields, the Boundary Element Method (BEM) is considered to evaluate stress values throughout the solid. Herein, the unknown boundary forces must be additionally calculated. As the photogrammetrically reconstructed deformed surfaces may be defined by several million points, the boundary displacement values of boundary-element models having a convenient number of nodes are determined based on an optimized displacement surface that best fits the real measured data. The results showed the effectiveness and potential application of the proposed methodology in several tasks to determine real-time stress distributions in structures.


Assuntos
Fotogrametria , Imagens de Fantasmas , Estresse Mecânico
11.
Mater Sci Eng C Mater Biol Appl ; 127: 112250, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34225889

RESUMO

Customized spinal implants fabricated by additive manufacturing have been increasingly used clinically to restore the physiological functions. However, the mechanisms and methods about the design for the spinal implants are not clear, especially for the reconstruction of multi-segment vertebral. This study aims to develop a novel multi-objective optimization methodology based on various normal spinal activities, to design the artificial vertebral implant (AVI) with lightweight, high-strength and high-stability. The biomechanical performance for two types of AVI was analyzed and compared under different loading conditions by finite element method. These implants were manufactured via selective laser melting technology and evaluated via compressive testing. Results showed the maximum Mises stress of the optimized implant under various load cases were about 41.5% of that of the trussed implant, and below fatigue strength of 3D printed titanium materials. The optimized implant was about 2 times to trussed implant in term of the maximum compression load and compression stiffness to per unit mass, which indicated the optimized implant can meet the safety requirement. Finally, the optimized implant has been used in clinical practice and good short-term clinical outcomes were achieved. Therefore, the novel developed method provides a favorable guarantee for the design of 3D printed multi-segment artificial vertebral implants.


Assuntos
Próteses e Implantes , Titânio , Fenômenos Biomecânicos , Análise de Elementos Finitos , Lasers , Impressão Tridimensional , Estresse Mecânico
12.
Sensors (Basel) ; 21(12)2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-34203702

RESUMO

In this paper we present a novel, cost-effective camera-based multi-axis force/torque sensor concept for integration into metallic load-bearing structures. A two-part pattern consisting of a directly incident and mirrored light beam is projected onto the imaging sensor surface. This allows the capturing of 3D displacements, occurring due to structure deformation under load in a single image. The displacement of defined features in size and position can be accurately analyzed and determined through digital image correlation (DIC). Validation on a prototype shows good accuracy of the measurement and a unique identification of all in- and out-of-plane displacement components under multiaxial load. Measurements show a maximum deviation related to the maximum measured values between 2.5% and 4.8% for uniaxial loads (Fx, Fy,Fz,Mz) and between 2.5% and 10.43% for combined bending, torsion and axial load. In the course of the investigations, the measurement inaccuracy was partly attributed to the joint used between the sensor parts and the structure as well as to eccentric load.


Assuntos
Transdutores , Estresse Mecânico , Suporte de Carga
13.
Int J Comput Dent ; 24(2): 125-131, 2021 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-34085498

RESUMO

AIM: The aim of the present study was to verify the possibility of obtaining an optimized prosthetic substructure using generic software, respecting the distribution loads and forces involved. What is considered to be original and innovative in this study is the possibility of designing the prosthetic substructure on the basis of the individual patient's chewing biomechanics, with the purpose of obtaining an even greater efficiency than a prosthesis designed according to a traditional method. MATERIALS AND METHODS: The starting standard triangulation language (STL) file was processed with Rhinoceros software and the tOpos plugin. It was decided to submit the entire prosthetic solution, intended as total volume, to structural analysis and topological optimization because the entire prosthesis is subjected to load during the chewing act. The software program was provided with information on the material, modulus, and direction of the applied forces. The objective was to optimize stiffness by maximizing volume. RESULTS: The volume of the final structure was 2% compared with the starting model and was a completely different design compared with the traditional model. This new design was characterized by trabeculations that reflect the normal bone architecture. The material was distributed on the basis of the load points as well as the direction and modulus of the applied force. CONCLUSIONS: After assessing the applicability of the proposed workflow and the results obtained thus far, the most important clinical implication is represented by the greater efficiency and the same resistance of the prosthesis obtained with topological optimization compared with that obtained with the traditional method.


Assuntos
Implantes Dentários , Fenômenos Biomecânicos , Planejamento de Prótese Dentária , Análise de Elementos Finitos , Humanos , Estresse Mecânico
14.
Sensors (Basel) ; 21(11)2021 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-34070904

RESUMO

The orthodontic miniscrew is driven into bone in a clockwise direction. Counter-clockwise rotational force applied to the implanted miniscrew can degrade the stability. The purpose of this three-dimensional finite element study was to figure out the effect of shifting the miniscrew head hole position from the long axis. Two miniscrew models were developed, one with the head hole at the long axis and the other with an eccentric hole position. One degree of counter-clockwise rotation was applied to both groups, and the maximum Von-Mises stress and moment was measured under various wire insertion angles from -60° to +60°. All Von-Mises stress and moments increased with an increase in rotational angle or wire insertion angle. The increasing slope of moment in the eccentric hole group was significantly higher than that in the centric hole group. Although the maximum Von-Mises stress was higher in the eccentric hole group, the distribution of stress was not very different from the centric hole group. As the positive wire insertion angles generated a higher moment under a counter-clockwise rotational force, it is recommended to place the head hole considering the implanting direction of the miniscrew. Clinically, multidirectional and higher forces can be applied to the miniscrew with an eccentric head hole position.


Assuntos
Procedimentos de Ancoragem Ortodôntica , Parafusos Ósseos , Análise de Elementos Finitos , Fenômenos Mecânicos , Estresse Mecânico
15.
Int J Mol Sci ; 22(11)2021 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-34073212

RESUMO

In the 1900s, researchers established animal models experimentally to induce atherosclerosis by feeding them with a cholesterol-rich diet. It is now accepted that high circulating cholesterol is one of the main causes of atherosclerosis; however, plaque localization cannot be explained solely by hyperlipidemia. A tremendous amount of studies has demonstrated that hemodynamic forces modify endothelial athero-susceptibility phenotypes. Endothelial cells possess mechanosensors on the apical surface to detect a blood stream-induced force on the vessel wall, known as "wall shear stress (WSS)", and induce cellular and molecular responses. Investigations to elucidate the mechanisms of this process are on-going: on the one hand, hemodynamics in complex vessel systems have been described in detail, owing to the recent progress in imaging and computational techniques. On the other hand, investigations using unique in vitro chamber systems with various flow applications have enhanced the understanding of WSS-induced changes in endothelial cell function and the involvement of the glycocalyx, the apical surface layer of endothelial cells, in this process. In the clinical setting, attempts have been made to measure WSS and/or glycocalyx degradation non-invasively, for the purpose of their diagnostic utilization. An increasing body of evidence shows that WSS, as well as serum glycocalyx components, can serve as a predicting factor for atherosclerosis development and, most importantly, for the rupture of plaques in patients with high risk of coronary heart disease.


Assuntos
Doença da Artéria Coronariana , Circulação Coronária , Células Endoteliais , Placa Aterosclerótica , Resistência ao Cisalhamento , Estresse Mecânico , Doença da Artéria Coronariana/metabolismo , Doença da Artéria Coronariana/patologia , Doença da Artéria Coronariana/fisiopatologia , Células Endoteliais/metabolismo , Células Endoteliais/patologia , Humanos , Placa Aterosclerótica/metabolismo , Placa Aterosclerótica/patologia , Placa Aterosclerótica/fisiopatologia , Placa Aterosclerótica/terapia
16.
Am J Dent ; 34(3): 157-162, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34143586

RESUMO

PURPOSE: To evaluate the effect of different substrate stiffness [sound dentin (SD), resin composite core (RC) or metal core (MC)] on the stress distribution of a zirconia posterior three-unit fixed partial denture (FPD). METHODS: The abutment teeth (first molar and first premolar) were modeled, containing 1.5 mm of axial reduction, and converging axial walls. A static structural analysis was performed using a finite element method and the maximum principal stress criterion to analyze the fixed partial denture (FPD) and the cement layers of both abutment teeth. The materials were considered isotropic, linear, elastic, homogeneous and with bonded contacts. An axial load (300 N) was applied to the occlusal surface of the second premolar. RESULTS: The region of the prosthetic connectors showed the highest tensile stress magnitude in the FPD structure depending on the substrate stiffness with different core materials. The highest stress peak was observed with the use of MC (116.4 MPa) compared to RC and SD. For the cement layer, RC showed the highest values in the molar abutment (14.7 MPa) and the highest values for the premolar abutment (14.4 MPa) compared to SD (14.1 and 13.4 MPa) and MC (13.8 and 13.3 MPa). Both metal core and resin composite core produced adequate stress concentration in the zirconia fixed partial denture during the load incidence. However, more flexible substrates, such as composite cores, can increase the tensile stress magnitude on the cement. CLINICAL SIGNIFICANCE: The present study shows that the choice of the cast core and metallic post by the resin composite core and fiberglass post did not improve the biomechanical behavior of the FPD. This choice must be performed based on clinical criteria (other) than mechanical.


Assuntos
Prótese Parcial Fixa , Zircônio , Análise do Estresse Dentário , Análise de Elementos Finitos , Estresse Mecânico
17.
Am J Dent ; 34(3): 171-176, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34143589

RESUMO

PURPOSE: To evaluate the stress distribution of inlays fabricated with restorative materials of different elastic moduli under two functional loading conditions by using three-dimensional (3D) finite element analysis (FEA) models of a second maxillary premolar. METHODS: A 3D model of a sound maxillary left second premolar and its supporting bone was generated in a previous study and reutilized under permission of the authors for the present study. Inlay models obtained from the sound tooth were then assigned according to the type and inherent elastic modulus of the restorative material used, as follows: microhybrid composite (Filtek Z250); indirect resin composite (Paradigm); lithium disilicate reinforced glass ceramic (IPS e.max Press); and type III gold alloy. The geometric models were then exported for 3D FEA. All materials were considered isotropic, homogeneous, and linear-elastic. A static load of 100 N was applied in two conditions: axially at both cusps (axial loading) and at the mesial marginal ridge (proximal loading). Maximum principal and von Mises stresses were used to analyze the stress distribution pattern in inlays and sound premolar models. RESULTS: Under axial loading condition, either resin composite, ceramic or type III gold alloy inlays generated a similar biomechanical behavior, especially in terms of stress distribution in the remaining tooth structure and cusp deflection. However, higher tensile stresses were observed along the proximal gingival margin of the preparation under proximal loading in the Z250 and Paradigm models, as well as a greater cusp deflection. In contrast, a deflection like the sound model was observed in the ceramic and gold inlay models. CLINICAL SIGNIFICANCE: Restorative materials with higher elastic modulus, such as dental ceramics and type III gold alloys, seem to be the best choice for maxillary premolars restored with inlays in the presence of occlusal contact on the marginal ridge.


Assuntos
Porcelana Dentária , Restaurações Intracoronárias , Dente Pré-Molar , Resinas Compostas , Materiais Dentários , Análise do Estresse Dentário , Análise de Elementos Finitos , Teste de Materiais , Estresse Mecânico
18.
Int J Mol Sci ; 22(9)2021 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-34066472

RESUMO

The mechanosensitive gene tenomodulin (Tnmd) is implicated in tendon maturation and repair. However, the mechanism by which mechanical loading regulates Tnmd's expression and its role in tenocyte migration is yet to be defined. Here, we show that Tnmd and migration were upregulated in uniaxial cyclic stress-stimulated tenocytes. The knockdown of Tnmd reduced cell migration in the presence and absence of mechanical loading, suggesting that Tnmd is involved in tenocyte migration. Moreover, the treatment of stress-stimulated tenocytes with the actin inhibitor latrunculin (Lat A), histone acetyltransferase inhibitor anacardic acid (ANA), or histone demethylases inhibitor GSK-J4 suppressed Tnmd expression and tenocyte migration. These results show that actin stress fiber formation and chromatin decondensation regulates Tnmd expression, which might then regulate tenocyte migration. Thus, this study proposes the involvement of the actin and chromatin mechanotransduction pathway in the regulation of Tnmd and reveals a novel role of Tnmd in tenocyte migration. The identification of Tnmd function in tenocyte migration provides insight into the molecular mechanisms involved in Tnmd-mediated tendon repair.


Assuntos
Actinas/metabolismo , Movimento Celular , Montagem e Desmontagem da Cromatina , Proteínas de Membrana/metabolismo , Estresse Mecânico , Tenócitos/citologia , Tenócitos/metabolismo , Animais , Células Cultivadas , Cromatina/metabolismo , Proteínas de Membrana/genética , Ratos Sprague-Dawley , Fibras de Estresse/metabolismo , Regulação para Cima/genética
19.
Molecules ; 26(10)2021 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-34070087

RESUMO

Fused filament fabrication (FFF) is a process used to manufacture oral forms adapted to the needs of patients. Polyethylene oxide (PEO) filaments were produced by hot melt extrusion (HME) to obtain a filament suitable for the production of amiodarone hydrochloride oral forms by FFF 3D printing. In order to produce personalized oral forms adapted to the patient characteristics, filaments used by FFF must be controlled in terms of mass homogeneity along filament. This work highlights the relation between filament mass homogeneity and its diameter. This is why the impact of filler excipients physical properties was studied. It has been showed that the particle's size distribution of the filler can modify the filament diameter variability which has had an impact on the mass of oral forms produced by FFF. Through this work it was shown that D-Sorbitol from Carlo Erba allows to obtain a diameter variability of less than 2% due to its unique particle's size distribution. Using the filament produced by HME and an innovating calibration method based on the filament length, it has been possible to carry out three dosages of 125 mg, 750 mg and 1000 mg by 3D printing with acceptable mass uniformity.


Assuntos
Fenômenos Físicos , Medicina de Precisão , Impressão Tridimensional , Sorbitol/química , Varredura Diferencial de Calorimetria , Tamanho da Partícula , Estresse Mecânico , Resistência à Tração , Termogravimetria , Fatores de Tempo , Difração de Raios X
20.
BMC Oral Health ; 21(1): 301, 2021 06 13.
Artigo em Inglês | MEDLINE | ID: mdl-34120593

RESUMO

BACKGROUND: The mechanics of double key loop (DKL) are not well defined, and this finite element study was designed to explore its force system. METHODS: A simplified 3-dimensional finite element model of single and double key loops with an archwire between the lateral incisor and second premolar was established in Ansys Workbench 17.0. Activation in Type-1 (retraction at the distal end), Type-2 (retraction at the distal key) and Type-3 (Type-2 plus ligation between keys) was simulated. The vertical force, load/deflection ratio and moment/force ratio of stainless-steel and titanium-molybdenum alloy (TMA) loops were calculated and compared. RESULTS: The double key loop generated approximately 40% of the force of a single key loop. Type-2 loading of DKL showed a higher L/D ratio than Type-1 loading with a similar M/F ratio. Type-3 loading of DKL showed the highest M/F ratio with a similar L/D ratio as single key loop. The M/F ratio in Type-3 loading increased with the decreasing of retraction force. The DKL of TMA produced approximately 40% of the force and moment compared with those of SS in all loading types. When activated at equal distances below 1 mm, the M/F ratios of SS and TMA DKL with equal preactivation angles were almost the same. CONCLUSION: The M/F ratio on anterior teeth increases with the preactivation angle and deactivation of DKL. The M/F ratio at a certain distance of activation mainly depends on the preactivation angle instead of the wire material. TMA is recommended as a substitute for SS in DKL for a lower magnitude of force.


Assuntos
Desenho de Aparelho Ortodôntico , Fios Ortodônticos , Ligas Dentárias , Análise do Estresse Dentário , Análise de Elementos Finitos , Humanos , Estresse Mecânico , Técnicas de Movimentação Dentária
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...