Nguyengrace3126

Significance Conditioning of the titanium surfaces with APP or LPP was not a significant influencing factor in the initial adhesion of the osteoblasts.Objective In this study the mechanical and adhesion properties of an experimental methacrylate based dentin bonding system containing a combination of spherical and layered platelet nanoparticles were investigated. The nanoparticles were first modified through surface graft polymerization of methacrylic acid in order to make the particles surface compatible with the bonding matrix resin. Materials and methods Graft free radical polymerization in aqueous media was performed to attach Poly (methacrylic acid) (PMA) chains onto the surface of Na-MMT nanoclay (Cloisite® Na+) and silica nanoparticles (Aerosil® 200). The hybrid PMA grafted nanoparticles (PMA-g-NC-Sil) were characterized using GPC, FTIR, TGA, and X-ray diffraction (XRD). Dentin adhesives containing different amounts of the hybrid modified nanoparticles were photopolymerized and their characteristics were studied using FTIR, TEM, SEM, EDXA, and XRD techniques. The adhesives containing different amounts of PMA-g-NC-Sil were applied to the conditioned hin bonding agent with enhanced shear bond strength through reinforcing the adhesive matrix and potential interactions between their carboxylic acid groups and the tooth structure. The dispersion stability of the nanoparticles was also dramatically improved by the surface modification of the nanoparticles.The fracture resistance of load-bearing trabecular bone is adversely affected by diseases such as osteoporosis. However, there are few published measurements of trabecular bone fracture toughness due to the difficulty of conducting reliable tests in small specimens of this highly porous material. A new approach is demonstrated that uses digital volume correlation of X-ray computed tomographs to measure 3D displacement fields in which the crack shape and size can be objectively identified using a phase congruency analysis. The criteria for crack propagation, i.e. fracture toughness, can then be derived by finite element simulation, with knowledge of the elastic properties.Atherosclerotic plaques are characterized by structural heterogeneity affecting aortic behaviour under mechanical loading. There is evidence of direct connections between the structural plaque arrangement and the risk of plaque rupture. As a consequence of aortic plaque rupture, plaque components are transferred by the bloodstream to smaller vessels, resulting in acute cardiovascular events with a poor prognosis, such as heart attacks or strokes. Hence, evaluation of the composition, structure, and biochemical profile of atherosclerotic plaques seems to be of great importance to assess the properties of a mechanically induced failure, indicating the strength and rupture vulnerability of plaque. The main goal of the research was to determine experimentally under uniaxial loading the mechanical properties of different types of the human abdominal aorta and human aortic atherosclerotic plaques identified based on vibrational spectra (ATR-FTIR and FT-Raman spectroscopy) analysis and validated by histological staining. The potential of spectroscopic techniques as a useful histopathological tool was demonstrated. Three types of atherosclerotic plaques - predominantly calcified (APC), lipid (APL), and fibrotic (APF) - were distinguished and confirmed by histopathological examinations. Compared to the normal aorta, fibrotic plaques were stiffer (median of EH for circumferential and axial directions, respectively 8.15 MPa and 6.56 MPa) and stronger (median of σM for APLc = 1.57 MPa and APLa = 1.64 MPa), lipidic plaques were the weakest (median of σM for APLc = 0.76 MPa and APLa = 0.51 MPa), and calcified plaques were the stiffest (median of EH for circumferential and axial directions, respectively 13.23 MPa and 6.67 MPa). Therefore, plaques detected as predominantly lipid and calcified are most prone to rupture; however, the failure process reflected by the simplification of the stress-stretch characteristics seems to vary depending on the plaque composition.This paper investigates the effects of multiple stents, with and without overlap, on the outcome of stent deployment in a patient-specific coronary artery using the finite element method. Specifically, the objective of this study is to reveal the effect of stent overlap on lumen gain, tissue damage and in-stent restenosis in percutaneous coronary intervention. Based on intravital optical coherency tomography imaging, three-dimensional model of a specific patient's coronary artery was developed, with two constituent layers (media and adventitia) and plaque, using Mimics. Hyperelastic models with damage, verified against experimental results, were used to describe stress-stretch responses of arterial layers and plaque. Abaqus CAE was used to create the models for Resolute Integrity™ drug-eluting stents and tri-folded expansion balloons. The results showed that lumen gain was improved by the overlapping stents than a single stent after deployment; however, damage to the media layer was greater, promoting a higher rate of in-stent restenosis. Meanwhile, the lumen gain achieved with the non-overlapping stents was smaller than that with the overlapping ones, due to an increased recoiling effect. Also, non-overlapping stents induced more tissue damage and higher rate of in-stent restenosis than overlapping stents. With respect to long-term clinical outcomes, the study recommended the use of a single stent where possible or multiple stents with minimal overlaps to treat long or angulated lesions.Many material properties of articular cartilage are anisotropic, particularly in the superficial zone where collagen fibers have a preferential direction. However, the anisotropy of cartilage wear had not been previously investigated. The objective of this study was to evaluate the anisotropy of cartilage material behavior in an in vitro wear test. click here The wear and coefficient of friction of bovine condylar cartilage were measured with loading in directions parallel (longitudinal) and orthogonal (transverse) to the collagen fiber orientation at the articular surface. An accelerated cartilage wear test was performed against a T316 stainless-steel plate in a solution of phosphate buffered saline with protease inhibitors. A constant load of 160 N was maintained for 14000 cycles of reciprocal sliding motion at 4 mm/s velocity and a travel distance of 18 mm in each direction. The contact pressure during the wear test was approximately 2 MPa, which is in the range of that reported in the human knee and hip joint. Wear was measured by biochemically quantifying the glycosaminoglycans (GAGs) and collagen that was released from the tissue during the wear test.