THE SIMULATION ASSESSMENT OF THE VENEERING LAYERS OF PROSTHETIC CROWNS IN CONCENTRATED CONTACT

Tribologia ◽  
2021 ◽  
Vol 293 (5) ◽  
pp. 39-50
Author(s):  
Wojciech Ryniewicz ◽  
Anna M. Ryniewicz ◽  
Łukasz Bojko ◽  
Konrad Mazur
Keyword(s):  
Shear Stress ◽  
Layered Structure ◽  
Layered Material ◽  
Strength Parameters ◽  
Metal Type ◽  
Cad Cam ◽  
Concentrated Loading ◽  
The Impact ◽  
External Loads ◽  
Distribution Of Stresses

The aim of the study is to simulate and analyse the distributions of stresses and resultant displacements during concentrated loading of the layered material compositions used in prosthetic crowns in order to assess their resistance and demonstrate the impact of strength parameters of the veneer and framework on the transfer of external loads. The research materials are samples replicating the layered structure of prosthetic crowns. The load-bearing layers were made using CAD/CAM technology, and the dedicated veneering layers were fired or polymerized on the frameworks and constituted the top structure for cooperation during occlusion. If the material of the veneering layer differs from the material building the framework, for example, in the ceramic-metal type, spreading of the resultant displacements to the framework and high values of shear stress at the border of the veneering layer and the framework may be unfavourable and cause the veneer layer to chip off. This distribution of stresses and displacements may have a much smaller impact on the ceramic veneering of a ceramic or glass-ceramic framework, as both layers are much more homogeneous in terms of material.

scholarly journals Solvothermal Preparation of Spherical Bi2O3 Nanoparticles Uniformly Distributed on Ti3C2Tx for Enhanced Capacitive Performance

2021 ◽  
Author(s):  
Tao Li ◽  
Xuefeng Chang ◽  
Lifang Mei ◽  
Xiayun Shu ◽  
Jidong Ma ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Chemical Stability ◽  
Layered Structure ◽  
Layered Material ◽  
Two Dimensional ◽  
Capacitive Performance ◽  
Solvothermal Preparation

Ti3C2Tx is a promising new two-dimensional layered material for supercapacitors with good electrical conductivity and chemical stability. However, Ti3C2Tx has problems such as collapse of the layered structure and low...

P3588The synergistic effect of NIRS-detected lipid-rich plaque and 5 different multidirectional wall shear stress metrics on human coronary plaque growth

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
E M J Hartman ◽  
A M Kok ◽  
A Hoogendoorn ◽  
F J H Gijsen ◽  
A F W Steen ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Synergistic Effect ◽  
Coronary Arteries ◽  
Wall Thickness ◽  
Plaque Progression ◽  
Lipid Rich Plaque ◽  
Plaque Growth ◽  
Wall Shear ◽  
The Impact

Abstract Introduction Local wall shear stress (WSS) metrics, high local lipid levels (as detected by near-infrared spectroscopy (NIRS)), as well as systemic lipid levels, have been individually associated with atherosclerotic disease progression. However, a possible synergistic effect remains to be elucidated. This study is the first study to combine WSS metrics with NIRS-detected local lipid content to investigate a potential synergistic effect on plaque progression in human coronary arteries. Methods The IMPACT study is a prospective, single centre study investigating the relation between atherosclerotic plaque progression and WSS in human coronary arteries. Patients with ACS treated with PCI were included. At baseline and after 1-year follow-up, patients underwent near-infrared spectroscopy intravascular ultrasound (NIRS-IVUS) imaging and intravascular doppler flow measurements of at least one non-culprit coronary artery. After one month, a CT angiography was made. CT derived centreline combined with IVUS lumen contours resulted in a 3D reconstruction of the vessel. The following WSS metrics were computed using computational fluid dynamics applying the vessel specific invasive flow measurements: time-average wall shear stress (TAWSS), relative residence time (RRT), cross-flow index, oscillatory shear index and transverse wall shear stress. Low TAWSS is known as pro atherogenic, in contrast to all the other shear stress metrics, at which a high magnitude is pro-atherogenic. The arteries were divided into 1.5mm/45° sectors. Based on NIRS-IVUS, wall thickness change over time was determined and NIRS positive sectors detected. Furthermore, per vessel the shear stress was divided into tertiles (low, intermediate, high). To investigate the synergistic effect of local lipids on shear stress related plaque growth, wall thickness change over time was related to the different shear stress metrics comparing the NIRS-positive with the NIRS-negative sectors. Results 15 non-culprit coronary arteries from the first 14 patients were analyzed (age 62±10 years old and 92.9% male). A total of 2219 sectors were studied (5.2%, N=130, NIRS-positive) for wall thickness changes. After studying all five shear stress metrics, we found for TAWSS and RRT that presence of lipids, as detected by NIRS, amplified the effect of shear stress on plaque progression (see figure). Sectors presenting with lipid-rich plaque, compared to NIRS-negative sectors, showed more progression when they were exposed to low TAWSS (p=0.07) or high RRT (p=0.012) and more regression in sectors exposed to high TAWSS (p=0.10) or low RRT (p=0.06). Delta wall thickness vs shear stress Conclusion We presented the first preliminary results of the IMPACT study, showing the synergistic effect of lipid rich plaque and shear stress on plaque progression. Therefore, intravascular lipid-rich plaque (NIRS) assessment has added value to shear stress profiling for the prediction of plaque growth, leading to improved risk stratification. Acknowledgement/Funding ERC starting grant 310457

scholarly journals The impact of the health condition of oaks from the Krotoszyn Plateau on the mechanical properties of timber structures

2015 ◽  
Vol 57 (4) ◽  
pp. 224-232
Author(s):  
Jarosław Siwiński ◽  
Katarzyna Kubiak ◽  
Miłosz Tkaczyk ◽  
Anna Mazur ◽  
Ryszard Rekucki
Keyword(s):  
Mechanical Properties ◽  
Health Condition ◽  
Health State ◽  
Timber Structures ◽  
Strength Parameters ◽  
Modified Method ◽  
Strength Tests ◽  
Prior Selection ◽  
The Impact ◽  
Selection Of

Abstract The study was conducted to perform a comparative analysis of the mechanical properties of wood samples derived from oaks in the Krotoszyn Plateau, which depend on the health state of the trees. Strength parameters of oak wood were calculated for selected diseased and healthy trees (according to the Roloff classification). The study was conducted by a modified method described in the standard Polish Norm PN EN 408+ A1: 2012. For testing, prior selection of wood samples showed that more wood samples of diseased trees compared with those of healthy oaks did not fulfil the Polish standard requirements. According to the method used, the average results of strength tests of timber structures from healthy oaks exhibited higher strength parameters than those of the diseased trees.

The Min-Max Load Criteria as a Measure of Machining Fixture Performance

1994 ◽  
Vol 116 (4) ◽  
pp. 500-507 ◽  
Author(s):  
E. C. DeMeter
Keyword(s):  
Convex Hull ◽  
Linear Model ◽  
Model Validation ◽  
Contact Region ◽  
Extreme Points ◽  
Simulation Experiments ◽  
Machining Operations ◽  
The Impact ◽  
External Loads ◽  
The Continuum

Spherical-tipped locators and clamps are often used for the restraint of castings during machining. For structurally rigid castings, contact region deformation and micro-slippage are the predominant modes of workpiece displacement. In turn contact region deformation and micro-slippage are heavily influenced by contact region loading. This paper presents a linear model for predicting the impact of locator and clamp placement on workpiece displacement throughout a series of machining operations. It illustrates how the continuum of external loads exerted on a workpiece during machining can be bounded within a convex hull, and how the extreme points of this hull are used within the model. Finally it describes the simulation experiments which were used for model validation.

scholarly journals The impact of particle shape on friction angle and resulting critical shear stress: an example from a coarse-grained, steep, megatidal beach

2013 ◽  
Vol 1 (1) ◽  
pp. 1187-1208 ◽  
Author(s):  
N. Stark ◽  
A. E. Hay ◽  
R. Cheel ◽  
C. B. Lake
Keyword(s):  
Shear Stress ◽  
Particle Motion ◽  
Particle Shape ◽  
Critical Shear Stress ◽  
Friction Angle ◽  
Sediment Dynamics ◽  
Tidal Range ◽  
Strong Increase ◽  
Elliptic Plate ◽  
The Impact

Abstract. The impact of particle shape on the friction angle, and the resulting critical shear stress on sediment dynamics, is still poorly understood. In areas characterized by sediments of specific shape, particularly non-rounded particles, this can lead to large departures from the expected sediment dynamics. The steep slope (1:10) of the mixed sand-gravel beach at Advocate Harbour was found stable in large-scale morphology over decades, despite a high tidal range of ten meters or more, and strong shorebreak action during storms. The Advocate sand (d < 2 mm) was found to have an elliptic, plate-like shape. Exceptionally high friction angles of the material were determined using direct shear, ranging from φ &amp;approx; 41–46°, while the round to angular gravel was characterized by φ = 33°. The addition of 25% of the elliptic sand to the gravel led to an immediate increase of the friction angle to φ = 38°. Furthermore, re-organization of the particles occurred during shearing, being characterized by a short phase of settling and compaction, followed by a pronounced strong dilatory behavior and an accompanying strong increase of shear stress. Long-term shearing (24 h) using a ring shear apparatus led to destruction of the particles without re-compaction. Finally, submerged particle mobilization was simulated using a tilted tray in a tank. Despite a smooth tray surface, particle motion was not initiated until reaching tray tilt angles of 31° and more, being 7° steeper than the latest gravel motion initiation. In conclusion, geotechnical laboratory experiments quantified the important impact of the elliptic, plate-like shape of Advocate Beach sand on the friction angles of both pure sand and sand-gravel mixtures. The resulting effect on initiation of particle motion was confirmed in tilting tray experiments. This makes it a vivid example of how particle shape can contribute to the stabilization of the beachface.

scholarly journals Effect of shear stress on the wall of technological pipelines at a gas condensate field on the intensity of carbon dioxide corrosion

2020 ◽  
Vol 244 ◽  
pp. 439-447
Author(s):  
Aleksandr Ponomarev ◽  
Aleksandr Yusupov
Keyword(s):  
Carbon Dioxide ◽  
Shear Stress ◽  
Flow Velocity ◽  
Three Dimensional ◽  
Gas Condensate ◽  
Carbon Dioxide Corrosion ◽  
Area Of Interest ◽  
Corrosion Intensity ◽  
Rational Operation ◽  
The Impact

The object of the study is a section of the gas and gas condensate collection system, consisting of an angle throttle installed on a xmas tree and a well piping located after the angle throttle. The aim of the study is to assess the impact of the flow velocity and wall shear stress (WSS) on the carbon dioxide corrosion rate in the area of interest and to come up with substantiated recommendations for the rational operation of the angle throttle in order to reduce the corrosion intensity. In the course of solving this problem, a technique was developed and subsequently applied to assess the influence of various factors on the rate of carbon dioxide corrosion. The technique is based on a sequence of different modeling methods: modeling the phase states of the extracted product, three-dimensional (solid) modeling of the investigated section, hydrodynamic flow modeling of the extracted product using the finite volume method, etc. The developed technique has broad possibilities for visualization of the obtained results, which allow identifying the sections most susceptible to the effects of carbon dioxide corrosion. The article shows that the average flow velocity and its local values are not the factors by which it is possible to predict the occurrence of carbon dioxide corrosion in the pipeline section after the angle throttle. The paper proves that WSS has prevailing effect on the corrosion intensity in the section after the angle choke. The zones of corrosion localization predicted according to the technique are compared with the real picture of corrosion propagation on the inner surface of the pipe, as a result of which recommendations for the rational operation of the angle throttle are formed.

scholarly journals Fracture resistance and 3D finite element analysis of machined ceramic crowns bonded to endodontically treated molars with two planes versus flat occlusal preparation designs: an in vitro study

F1000Research ◽  
2021 ◽  
Vol 8 ◽  
pp. 1020
Author(s):  
Omnia Nabil ◽  
Carl Hany Halim ◽  
Ashraf Hassan Mokhtar
Keyword(s):  
Stress Distribution ◽  
Fracture Resistance ◽  
Element Analysis ◽  
3D Finite Element ◽  
Mean Values ◽  
Group I ◽  
Group Ii ◽  
The Impact ◽  
Preparation Design ◽  
Distribution Of Stresses

Background: The flat occlusal preparation design (FOD) of posterior teeth offers promising results of fracture resistance and stress distribution, but its application in vital teeth is limited as there may be a danger of pulp injury. Although this danger is omitted in endodontically treated teeth, there is no research work assessing the impact of FOD on the fracture resistance and distribution of stresses among these teeth. The aim of this study was to assess the impact of FOD of endodontically treated molars on the fracture resistance and distribution of stresses among a ceramic crown-molar structure when compared to the two planes occlusal preparation design (TOD). Methods: 20 human mandibular molars were endodontically treated and distributed equally to two groups: Group I (TOD) and Group II (FOD). Ceramic CAD/CAM milled lithium disilicate (IPS e.max CAD) crowns were produced for all preparations and adhered using self-adhesive resin cement. Using a universal testing machine, the fracture resistance test was performed. The fractured samples were examined using a stereomicroscope and scanning electron microscope to determine modes of failure. Stress distribution was evaluated by 3D finite element analysis, which was performed on digital models of endodontically treated mandibular molars (one model for each design). Results: Group II recorded statistically non-significant higher fracture resistance mean values (3107.2± 604.9 N) than Group I mean values (2962.6 ±524.27 N) as indicated by Student’s t-test (t=0.55, p= 0.57). Also, Group II resulted in more favorable failure mode as compared to Group I. Both preparation designs yielded low von-Mises stresses within the factor of safety. However, the stress distribution among different layers of the model differed. Conclusions: FOD having comparable fracture strength to TOD and a more favorable fracture behavior can be used for the preparation of endodontically treated molars.

scholarly journals A Bayesian approach to modelling the impact of hydrodynamic shear stress on biofilm deformation

PLoS ONE ◽  
2018 ◽  
Vol 13 (4) ◽  
pp. e0195484 ◽  
Author(s):  
Oluwole K. Oyebamiji ◽  
Darren J. Wilkinson ◽  
Pahala Gedara Jayathilake ◽  
Steve P. Rushton ◽  
Ben Bridgens ◽  
...  
Keyword(s):  
Shear Stress ◽  
Bayesian Approach ◽  
Hydrodynamic Shear ◽  
The Impact

Effect of In-office Bleaching on Color, Translucency, and Whiteness Variations in CAD-CAM Monolithic Materials

2021 ◽  
Author(s):  
RG Fonseca ◽  
RC Peńa ◽  
R Simóes ◽  
AC Ramos ◽  
LN Dovigo
Keyword(s):  
Optical Properties ◽  
Computer Aided Design ◽  
Calculated Data ◽  
Color Difference ◽  
Deionized Water ◽  
Stain Removal ◽  
Computer Aided ◽  
Cad Cam ◽  
Aided Design ◽  
The Impact

SUMMARY Little is known about the impact of bleaching on the optical properties of computer-aided design and computer-aided manufactured (CAD-CAM) monolithic materials. The aim of the present study was to evaluate the effect of one session of in-office bleaching on stain removal, staining susceptibility, translucency, and whiteness variations of CADCAM monolithic materials. Disks were fabricated from Lava Ultimate (LU), Vita Enamic (VE), Vita Suprinity (VS), and IPS e.max CAD (IPS). A spectrophotometer was used to register Commission Internationale de l’Eclairage L*a*b* coordinates. For stain removal, 80 specimens from each material were assessed at baseline (R0) and after immersion in deionized water or coffee for 365 days followed or not by bleaching with 40% hydrogen peroxide (R1). For staining susceptibility, 80 specimens from each material were analyzed at baseline (R0’), and after having been bleached or not and immersed in deionized water or coffee (R1’). Both analyses were calculated as the color difference (ΔE00) between R1-R0 and R1’-R0’, respectively. Differences in translucency (ΔTP00) and whiteness (ΔWID) between R1-R0 and R1’-R0’ were also calculated. Data were analyzed by three-way ANOVA and the Games-Howell post hoc test (α=0.05). Clinical significance was based on 50%:50% perceptibility and acceptability thresholds for ΔE00, ΔTP00 and ΔWID, respectively. Surfaces were analyzed by scanning electron microscopy. Coffee increased ΔE00 in LU, VE, and VS, and decreased their translucency and whiteness, whereas the IPS had only its whiteness affected. Bleaching after immersion in coffee decreased ΔE00 in LU and VE, and increased translucency and whiteness of LU, VE, and VS. No effect was observed on IPS. Bleaching before immersion in coffee decreased translucency of LU, but within the acceptable interval, while VE exhibited lower ΔE00, and became more translucent and less dark. Both VS and IPS were not affected. One session of in-office bleaching benefited optical properties of the previously stained LU, VE, and VS, without increasing their susceptibility to staining or adversely providing clinically unacceptable variations in their translucency and whiteness. All variations exhibited by the IPS were below the perceptible threshold.

From Sketches and Installations to Bioinspired 5D Printing Models

2021 ◽  
pp. 365-387
Author(s):  
Silvia Titotto
Keyword(s):  
Decision Making ◽  
Additive Manufacturing ◽  
Future Development ◽  
Smart Cities ◽  
Virtual Prototyping ◽  
Interdisciplinary Approach ◽  
Biologically Inspired ◽  
Digital Twins ◽  
Cad Cam ◽  
The Impact

This chapter opens up discussions upon the relevance of interaction of representations and data visualization modes for smart cities design, planning, and development that occur beyond paper and computer drawing. Although many practitioners usually relate smart cities and digital twins design exclusively to CAD/CAM/CAE and BIM methods, processes, and tools, a wider pool of techniques and forms of expression might be the key to a more accurate and comprehensive way of simulating the several kinds of alterations that happen in the planned built environment. The chapter deals with the study of concepts that relate to both physical and virtual prototyping, which underlines an interdisciplinary approach to design and the impact of integrating biologically inspired principles from different backgrounds to the field of smart cities design. In this regard, biomimetics and additive manufacturing may play key roles in smart city's modeling design and the frontier technology of 5D printing reveals real-time decision-making programmable 4D printing process as a potential future development.

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