Low Shear Stress Research Articles

Endovascular Management of a Giant Aortic Arch Aneurysm Diverticulum: A Case Report

Abstract Background Thoracic aortic diverticulum, or Kommerell's aneurysm, is a developmental outpouching at the anteromedial aspect of the thoracic aorta, specifically at the site of the aortic isthmus, with an incidence of up to 9% in adults. It represents a notable anatomical variation that, over time, undergoes aneurysmal dilatation, posing the risk of rupture. Case We present a 66-year-old male initially referred with a 7.35 cm giant thoracic aortic arch diverticulum (TAD). It was initially discovered incidentally as a 2.1 cm type 3 Salomonowitz; however, it subsequently increased to 7.36 cm following the third COVID-19 infection with cytokine storm. He underwent a right-to-left carotid necklace c-shaped configuration crossover bypass using an 8 mm ringed Dacron silver graft. Six weeks post-bypass, the patient underwent a successful repair of TAD using the NEXUS-Endospan-Artivion system (ArtivionTM, GA 30144, USA), employing a double inner branch to the innominate and left subclavian artery through a single groin approach. Postoperatively, he recovered fully without any neurological or cardiovascular issues with no signs of endoleaks, graft migration, or separation. Conclusions The saccular nature of the aneurysm at the arch reveals a distinctive set of challenges, mainly the low wall shear stress, which exposes their malignant potential, emphasizing the crucial need for intervention, especially when surpassing the critical 30 mm threshold. This premiere marks a significant milestone by introducing the ‘IDEALIST’ Artivion/Endospan Nexus, which pioneers a total endovascular approach post-CE marking, ushering in a new era in aortic arch interventions.

Evaluation of Physicochemical, Microstructure Parameters (Q3) and Performance Attributes of Commercial Ketoprofen Gels.

In vitro methods for quality and equivalence assessment of semi-solid products applied to the skin have increasingly garnered attention because in vivo bioequivalence studies is high cost, complexity, and time-consuming. Regulatory authorities established draft guidelines that outline a modular framework demanding qualitative, quantitative, microstructure and product performance equivalence to support generic products. In line with these guidelines, our study aimed to evaluate the relationship between microstructure and performance attributes in both originator and generic semi-solid products applied to the skin. In this context, reference and three generics of ketoprofen gel were selected as models for semi-solid formulations. Microstructure of all products was assessed regarding pH, specific gravity, drying rate, formulation rheology and potential drug polymorphism. Additionally, performance attributes of products were evaluated using in vitro release testing and in vitro permeation testing. Polymorphism and drying rate data showed no significant difference in microstructure of ketoprofen gels. All tested products exhibited pseudo-plastic flow behavior with thixotropic characteristic. However, differences in pH, specific gravity and viscosity values at low shear stress were observed between reference product and generic products, according to EMA guidance. Although IVRT outcomes did not entirely align with Q3 attributes, IVRT results for reference product versus Generic Product-I and Generic Product-II met the acceptance limits according to FDA guidance, which differs from EMA's assessment. Furthermore, in vitro release rate results were consistent with IVPT data. Consequently, it can be concluded that microstructure of semi-solid products applied to the skin may not consistently correlate with performance attributes due to various alternations influenced by manufacturing process parameters and/or formulation components.

Low shear stress induces vascular endothelial cells apoptosis via miR-330 /SOD2 /HSP70 signaling pathway.

Atherosclerosis (AS) is a chronic disease initiated by vascular endothelial dysfunction, with low shear stress (SS) being a critical inducing factor in this dysfunction. Apoptosis, a form of programmed cell death, is closely associated with AS progression. However, the impact of low SS on endothelial apoptosis and its specific molecular mechanisms remains unclear. Our study revealed that low SS induces apoptosis in endothelial cells and contributes to endothelial dysfunction. Under low SS conditions, miR-330 expression was markedly upregulated, which subsequently targeted and inhibited SOD2 expression, leading to ROS accumulation and oxidative stress. Overexpression of SOD2 under low SS conditions markedly elevated HSP70 expression, contributing to endothelial homeostasis. However, when HSP70 expression was inhibited in the context of SOD2 overexpression, there was a significant increase in pro-apoptotic proteins (BAX and cleaved-caspase-3) and total apoptosis rate, along with a significant reduction in endothelial function markers such as nitric oxide and endothelial nitric oxide synthase. Notably, our experiments indicated no direct interaction between SOD2 and HSP70. Furthermore, inhibiting ROS production significantly raised HSP70 expression, suggesting that SOD2 regulates HSP70 in an indirect process involving ROS. In summary, our findings elucidate that low SS induces endothelial apoptosis and dysfunction through the miR-330/SOD2/HSP70 signaling pathway, providing valuable insights into AS intervention and prevention.

Evaluation of the impact of hollow fiber pore size and membrane material on virus concentration using a handheld hollow fiber method.

Virus concentration using hollow fibers is widely used for vaccine production to maintain viral infectivity with low shear stress and to allow for easier scale-up of production. However, research laboratories often have limited available viral materials at the early stage of vaccine development, making it difficult to find an optimal hollow-fiber. In addition, few research articles have reported on optimizing hollow fiber pore size and membrane structure for virus concentration. In this study, the previously established handheld hollow fiber virus concentration method was modified to reduce the sample volume required and to enable simple and easy hollow fiber screening. The handheld hollow fiber screening method for virus concentration was confirmed to be effective using Zika as a model virus.

Abstract WP271: Low Endothelial Shear Stress is Associated with Early Neurological Deterioration in Patients with Single Subcortical Infarction

Abstract WP271: Low Endothelial Shear Stress is Associated with Early Neurological Deterioration in Patients with Single Subcortical Infarction

Abstract TP7: Comparison of inflammatory clot markers in higher and lower shear stress environments: is there really that big of a difference?

Abstract TP7: Comparison of inflammatory clot markers in higher and lower shear stress environments: is there really that big of a difference?

Computational fluid dynamics to simulate stenotic lesions in coronary end-to-side anastomosis.

End-to-side anastomosis is common in coronary artery bypass grafting, although restrictive suturing can narrow the anastomosis. We evaluated ex vivo end-to-side models by numerically simulating fluid dynamics to compare various degrees of stenotic anastomoses to predict haemodynamic effects. A carotid artery was grafted via an end-to-side anastomosis onto the left anterior descending artery of a porcine heart, with liquid silicone injected into the vessels. The end-to-side image was acquired via multidetector computed tomography for reference, and models of longitudinal shortening and bilateral narrowing were created with 25%, 50%, 75%, along with 90%, and 100% stenosis in the native coronary artery. Haemodynamics were analyzed using computational fluid dynamics simulations to calculate streamlines, wall shear stress, and oscillatory shear index. In the reference model, the graft inflow impinged on the floor of the native artery, creating a recirculating vortex and a high oscillatory shear index region near the heel. As the graft flow angle increased with longitudinal stenosis, bilateral stenosis generated helical flow near the lateral wall of the native artery, worsening with increased stenosis. At 75% stenosis, both longitudinal shortening and bilateral narrowing caused abnormal flow separation, with low wall shear stress and high oscillatory regions forming distal to the toe of the anastomosis. Computational fluid dynamics modelling predicts that end-to-side anastomoses with 75% longitudinal or bilateral stenosis are at a risk of intimal hyperplasia causing graft failure, while anastomotic stenosis <50% indicates acceptable haemodynamics. Future studies should explore long-term clinical outcomes with suboptimal surgical anastomotic construction.

Transcriptional Responses of In Vitro Blood–Brain Barrier Models to Shear Stress

Endothelial cells throughout the body sense blood flow, eliciting transcriptional and phenotypic responses. The brain endothelium, known as the blood–brain barrier (BBB), possesses unique barrier and transport properties, which are in part regulated by blood flow. We utilized RNA sequencing to analyze the transcriptome of primary cultured rat brain microvascular endothelial cells (BMECs), as well as three human induced pluripotent stem cell-derived models. We compared the transcriptional responses of these cells to either low (0.5 dyne/cm2) or high (12 dyne/cm2) shear stresses, and subsequent analyses identified genes and pathways that were influenced by shear including key BBB-associated genes (SLC2A1, LSR, PLVAP) and canonical endothelial shear-stress-response transcription factors (KLF2, KLF4). In addition, our analysis suggests that shear alone is insufficient to rescue the de-differentiation caused by in vitro primary BMEC culture. Overall, these datasets and analyses provide new insights into the influence of shear on BBB models that will aid in model selection and guide further model development.

Sensitivity of coronary hemodynamics to vascular structure variations in health and disease

Local hemodynamics play an essential role in the initiation and progression of coronary artery disease. While vascular geometry alters local hemodynamics, the relationship between vascular structure and hemodynamics is poorly understood. Previous computational fluid dynamics (CFD) studies have explored how anatomy influences plaque-promoting hemodynamics. For example, areas exposed to low wall shear stress (ALWSS) can indicate regions of plaque growth. However, small sample sizes, idealized geometries, and simplified boundary conditions have limited their scope. We generated 230 synthetic models of left coronary arteries and simulated coronary hemodynamics with physiologically realistic boundary conditions. We measured the sensitivity of hemodynamic metrics to changes in bifurcation angles, positions, diameter ratios, tortuosity, and plaque topology. Our results suggest that the diameter ratio between left coronary branches plays a substantial role in generating adverse hemodynamic phenotypes and can amplify the effect of other geometric features such as bifurcation position and angle, and vessel tortuosity. Introducing mild plaque in the models did not change correlations between structure and hemodynamics. However, certain vascular structures can induce ALWSS at the trailing edge of the plaque. Our analysis demonstrates that coronary artery vascular structure can provide key insight into the hemodynamic environments conducive to plaque formation and growth.

Convective forces contribute to post‐traumatic degeneration after spinal cord injury

AbstractSpinal cord injury (SCI) initiates a complex cascade of chemical and biophysical phenomena that result in tissue swelling, progressive neural degeneration, and formation of a fluid‐filled cavity. Previous studies show fluid pressure above the spinal cord (supraspinal) is elevated for at least 3 days after injury and contributes to a phase of damage called secondary injury. Currently, it is unknown how fluid forces within the spinal cord itself (interstitial) are affected by SCI and if they contribute to secondary injury. We find spinal interstitial pressure increases from −3 mmHg in the naive cord to a peak of 13 mmHg at 3 days post‐injury (DPI) but relatively normalizes to 2 mmHg by 7 DPI. A computational fluid dynamics model predicts interstitial flow velocities up to 0.9 μm/s at 3 DPI, returning to near baseline by 7 DPI. By quantifying vascular leakage of Evans Blue dye after a cervical hemi‐contusion in rats, we confirm an increase in dye infiltration at 3 DPI compared to 7 DPI, suggestive of higher fluid velocities at the time of peak fluid pressure. In vivo expression of the apoptosis marker caspase‐3 is strongly correlated with regions of interstitial flow at 3 DPI, and exogenously enhancing interstitial flow exacerbates tissue damage. In vitro, we show overnight exposure of neuronal cells to low pathological shear stress (0.1 dynes/cm2) significantly reduces cell count and neurite length. Collectively, these results indicate that interstitial fluid flow and shear stress may play a detrimental role in post‐traumatic neural degeneration.

Shear stress unveils patient-specific transcriptional signatures in PAH: Towards personalized molecular diagnostics.

Rationale: Pulmonary arterial hypertension (PAH) is a life-threatening disorder characterized by increased pulmonary blood pressures and regional inhomogeneities in flows, with diagnostic and treatment challenges arising from diverse underlying pathogenic mechanisms. Conventional in vitro models often obscure the mechanistic nuances of PAH by failing to replicate the dynamic mechanical environment of the diseased lung, limiting the identification of specific molecular patterns. To address this, we employed an in vitro shear stress model simulating physiological or pathological conditions to explore the transcriptional heterogeneity of human pulmonary microvascular endothelial cells (hPMECs) from PAH patients and healthy controls within their respective biomechanical context. Methods & Results: hPMECs from PAH patients and controls were exposed to static, low shear stress (LSS), and high shear stress (HSS) conditions, followed by bulk RNA-sequencing. While increasing shear stress resulted in a greater number of differentially expressed genes, traditional grouped analysis showed minimal overall transcriptional differences. Further, pathway enrichment analysis indicated common shear-induced responses in both groups, suggesting that standard analysis methods may mask meaningful disease-specific changes. Crucially, detailed dimensionality reduction analyses revealed pronounced inter-patient variability among PAH donors in response to increasing shear stress, facilitating the identification of 398 genes driving this transcriptional heterogeneity. Unsupervised clustering of these high-variability genes enabled the sub-classification of patients based on their unique transcriptomic profiles, each linked to specific combinations of PAH associated pathogenic pathways such as mesenchymal transition, inflammation, metabolism, extracellular matrix remodeling, and cell cycle/DNA damage signaling. Importantly, re-analysis of published peripheral blood mononuclear cell (PBMC) omics data from PAH patients confirmed the clinical feasibility to utilize these high-variability genes as a non-invasive, accessible approach for molecular patient stratification. Conclusion: Our study uncovers patient-specific transcriptomic patterns in PAH, providing a novel molecular sub-classification strategy. These findings represent a significant step toward personalized molecular diagnostics in PAH and eventual therapeutic interventions for clinically well-defined PAH patients, with potential applications in clinically accessible cell populations such as PBMCs.

Endothelial cell (EC)-specific CTGF/CCN2 Expression Increases EC Reprogramming and Atherosclerosis.

Arterial endothelial cells (ECs) reside in a complex biomechanical environment. ECs sense and respond to wall shear stress. Low and oscillatory wall shear stress is characteristic of disturbed flow and commonly found at arterial bifurcations and around atherosclerotic plaques. Disturbed flow is pro-inflammatory to ECs. Arteries also stiffen with aging and/or the onset of vascular disease. ECs sense and respond to stiffening in a pro-fibrotic manner. Thus, flow and stiffening disturbances elicit EC responses that promote pathologic arterial remodeling. However, the pathways elicited by ECs under pathologic stiffening and disturbed flow are not well understood. The objective of this work was to discover and test the modifiability of key pathways in ECs. To do this we used the partial carotid ligation model to impose disturbed flow onto the precociously stiffened fibulin-5 knockout (Fbln5-/-) mouse carotid arteries. Biomechanical testing demonstrated that Fbln5-/- arteries under disturbed flow approximate the stiffness ratio of diseased human arteries, and the ECs in these Fbln5-/- arteries underwent rapid reprogramming via endothelial to mesenchymal transition (EndMT). Under atherogenic conditions, disturbed flow Fbln5-/- arteries developed more vulnerable plaques than the wild type (WT) mouse arteries. Connective tissue growth factor/cellular communication network factor 2 (Ctgf/Ccn2) was upregulated in vivo in ECs with aging, with stiffening in the Fbln5-/- arteries, and increased again by disturbed flow under stiffened conditions, supporting CTGF as a key biomarker for flow and stiffening. This was validated by immunohistochemistry, which demonstrated increased CTGF deposition in areas of disturbed flow in patient carotid endarterectomy and peripheral artery disease (PAD) specimens. Finally, to test the role of CTGF in regulating and combining these processes, we created an EC-specific Ctgf knockout (Ctgfecko). We identified that carotid arteries under disturbed flow and atherogenic conditions in male Ctgfecko, but not female, mice had decreased plaque area compared to WT control mice. We then tested the Ctgf expression in the carotid endothelium exposed to disturbed or stable flow in WT and Fbln5-/- mice. Here we found that under disturbed flow male mice had greater Ctgf expression than female mice. This work demonstrates that stiffened + disturbed flow conditions drive EC reprogramming, that CTGF is increased by these conditions, and that this increase is more prominent in male carotid arteries. Future exploration of sex-based differences in these fibrotic pathways are warranted to develop targeted therapeutics to limit pathologic arterial remodeling under pathologically stiffened + disturbed flow environments.

Rupture prediction of medium to large-sized abdominal aortic aneurysm combining wall shear stress-related parameters and anatomical characteristics: A computational, experimental, and statistical analysis

A diameter of 50 or 55 mm is the primary clinical criterion for assessing abdominal aortic aneurysm (AAA) rupture risk. However, although larger diameters may induce higher rupture risk, not all AAAs exceeding intervention threshold will rupture, highlighting the need for indicators besides diameter to help rupture prediction and treatment of AAA ≥ 50 mm. The study aims to combine computation, experiment, and statistics to establish rupture prediction models for AAAs ≥ 50 mm and explore the optimal predictors of AAA rupture with different diameters by anatomical and hemodynamic characteristics. Through numerical simulation and in vitro experiment, morphological and hemodynamic parameters were obtained from 82 AAAs (41 ruptured) ≥ 50 mm. The results of significance test and logistic regression indicate that low time-averaged wall shear stress (TAWSS) of AAA and maximum diameter of common iliac artery, and high oscillatory shear index (OSI) of AAA, TAWSS of iliac artery and tortuosity of abdominal aorta increase rupture risk of AAA ≥ 50 mm. The prediction model combining these variables was established with high accuracy (area under curve = 0.978). Furthermore, univariable analyses for AAAs of different diameters imply the OSI is a risk factor for AAA rupture of 50–65 mm, while higher TAWSS decreases the risk of AAA rupture of 65–80 and ≥ 80 mm. The findings may contribute to accurate rupture prediction and personalized management of AAAs ≥ 50 mm and with different diameters, and further demonstrate potential value and application prospects of combining morphology and hemodynamics in clinical practice.

Inverse energy cascade in turbulent Taylor–Couette flows

The inverse energy cascade in turbulent Taylor–Couette flow is studied in line with the results of the large eddy simulation. The simulation results show that the inverse energy cascade first occurs within the core region of the flow channel of the Taylor–Couette flow at higher Reynolds numbers. It is uncovered that this phenomenon is induced by the pulsed zero shear stress resulting from the singularities of the Navier–Stokes equation. In the core area between the two cylinders, the shear stress is nearly zero at higher Reynolds numbers. The turbulence generated there has high turbulent energy due to discontinuity of the tangential velocity. Since the energy transfer between the fluid layers is inhibited due to the low shear stress, the turbulent energy cannot be transferred along the radial direction, and small-scale vortices with high turbulent energy are produced. These small-scale vortices are located with the large-scale vortices and cannot be dissipated owing to low shear stress. A peak in the energy spectrum at the middle frequency (or wave number) is formed due to the concentration of the small-scale vortices. As the number of the singular points of the Navier–Stokes equation increases with the increasing Reynolds number, the region with zero shear stress expands along the radial direction, intensifying nonlinear instability and energy accumulation. This, in turn, leads to more prominent peaks in the energy spectrum, resulting in a more pronounced inverse energy cascade.

Impact of Vein Wall Hyperelasticity and Blood Flow Turbulence on Hemodynamic Parameters in the Inferior Vena Cava with a Filter.

Inferior vena cava (IVC) filters are vital in preventing pulmonary embolism (PE) by trapping large blood clots, especially in patients unsuitable for anticoagulation. In this study, the accuracy of two common simplifying assumptions in numerical studies of IVC filters-the rigid wall assumption and the laminar flow model-is examined, contrasting them with more realistic hyperelastic wall and turbulent flow models. Using fluid-structure interaction (FSI) and computational fluid dynamics (CFD) techniques, the investigation focuses on three hemodynamic parameters: time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT). Simulations are conducted with varying sizes of clots captured in the filter. The findings show that, in regions of high wall shear stress, the rigid wall model predicted higher TAWSS values, suggesting an increased disease risk compared to the hyperelastic model. However, the laminar and turbulent flow models did not show significant differences in TAWSS predictions. Conversely, in areas of low wall shear stress, the rigid wall model indicated lower OSI and RRT, hinting at a reduced risk compared to the hyperelastic model, with this discrepancy being more evident with larger clots. While the predictions for OSI and TAWSS were closely aligned for both laminar and turbulent flows, divergences in RRT predictions became apparent, especially in scenarios with very large clots.

Feasibility of 4D-flow CMR for haemodynamic characterization in hypertrophic cardiomyopathy after septal myectomy with and without anterior mitral valve leaflet extension.

The common surgical treatment in patients with obstructive hypertrophic cardiomyopathy is septal myectomy. This involves resection of a segment of the myocardial septum and can be performed with and without concomitant anterior mitral valve leaflet extension (AMVLE). While both approaches have satisfying clinical outcomes, there is a lack of data regarding the added value of concomitant AMVLE. In particular, their impact on postoperative haemodynamics remains unexplored. Therefore, we conducted a study to assess the feasibility of utilizing four-dimensional-flow cardiac magnetic resonance imaging (4D-flow cardiac magnetic resonance imaging (CMR)) to investigate postoperative haemodynamic differences among both surgical approaches. In this feasibility study, nine subjects underwent 4D-flow CMR evaluation, including three patients who underwent isolated myectomy, three patients with myectomy + AMVLE and three healthy controls. Primary end-points were aortic wall shear stress, left ventricular outflow tract (LVOT) peak velocity and peak kinetic energy in the LVOT and ascending aorta. Results showed that patients who underwent myectomy with concomitant AMVLE exhibited (i) lower aortic wall shear stress (-21.2%), (ii) lower LVOT peak velocity (-6.3%), (iii) higher kinetic energy in the LVOT (+10.8%) and (iv) lower kinetic energy in the ascending aorta (-28.8%) compared to patients who underwent isolated myectomy. Patients undergoing additional AMVLE exhibited a better trend towards the haemodynamic reference values from healthy controls compared to patients undergoing isolated myectomy. Our findings underscore the feasibility of 4D-flow CMR to assess postoperative haemodynamic differences in hypertrophic cardiomyopathy patients undergoing different surgical approaches. This highlights the potential of 4D-flow CMR to compare surgical strategies based on postoperative haemodynamics. Dutch National Medical Ethics Committee, registration number 2022.0078.

Near-Wall Slow Flow Contributes to Wall Enhancement of Middle Cerebral Artery Bifurcation Aneurysms on Vessel Wall MRI.

Background: The mechanism of aneurysm wall enhancement (AWE) in middle cerebral artery (MCA) bifurcation aneurysms on vessel wall magnetic resonance imaging (VW-MRI) remains unclear. We aimed to explore the morphologically related hemodynamic mechanism for the AWE of MCA bifurcation aneurysms. Methods: Patients with unruptured MCA bifurcation aneurysms undergoing VW-MRI were enrolled. Logistic regression analyses were performed to determine the risk factors for AWE. Based on the results of retrospective analyses, bifurcation aneurysm silicone models with a specific aspect ratio (AR) were designed and underwent VW-MRI with different inlet velocities. Computational fluid dynamics (CFD) analyses were conducted on both silicone models and patients' aneurysms. Results: A total of 104 aneurysms in 95 patients (mean age 60; 34 males) were included for baseline analysis and morphological analysis. Logistic regression analysis indicated AR (OR, 5.92; 95% CI, 2.00-17.55; p = 0.001) was associated with AWE. In the high-AR group of 45 aneurysms with AWE, the aneurysm sac exhibited lower blood flow velocity, lower wall shear stress, a larger proportion of low-flow regions and higher wall enhancement values. In total, 15 silicone models were analyzed, divided into three subgroups based on neck width (4 mm, 6 mm, and 8 mm). Each subgroup contained aneurysms with five different ARs: 1.0, 1.25, 1.5, 1.75, and 2.0. In silicone models, contrast enhancement (CE) was mainly located beneath the dome of the aneurysm wall. With the same inlet velocity, CE gradually increased as the AR increased. Similarly, at the same AR, CE increased as the inlet velocity decreased. CFD demonstrated a moderate positive correlation between the near-wall enhancement index and the ratio of the low-velocity area (r = 0.6672, p < 0.001). Conclusions: The AR is associated with the AWE of MCA bifurcation aneurysms. A high AR may promote wall enhancement by causing near-wall slow flow.

Comprehensive study of Schottky-gated p-channel GaN field-effect transistors

In this work, a comprehensive study of Schottky-gated p-channel GaN field-effect transistors (GaN PFETs) with an energy-band modulated AlGaN barrier layer, a variable gate structure, and various densities of holes in the p-GaN layer is demonstrated to optimize electrical performance. The design rules for high-performance Schottky-gated GaN PFETs not only offer diverse pathways to achieve enhancement-mode operation but also improve output current density. Based on the design rules, a high-performance enhancement-mode GaN PFET with a high ION/IOFF ratio of 3 × 106, a low SS of 130 mV/dec, and a negative VTH of −1.09 V is fabricated, which is conducive to promoting the development of the low-power GaN complementary metal–oxide–semiconductor driving circuits.

Endocrown-retained fixed partial dentures: Revolutionizing tooth restoration or risky business? A finite element study

Aim: This study aimed to compare the biomechanical performance of endocrown-retained and post-and-core-retained fixed partial dentures (FPDs), focusing on stress distribution, tensile, and shear stress. Materials and Methods: Finite element analysis was used to simulate occlusal loading on two FPD designs: endocrown-retained zirconia and post-and-core-retained zirconia which were subjected to a simulated occlusal load of 150 N. Stress distribution was analyzed using von Mises stress, tensile stress, and shear stress. Material properties for zirconia, resin cement, enamel, dentin, bone, Periodontal ligament (PDL), and fiber post were incorporated. Results: The endocrown design showed lower von Mises stress (176.35 MPa) than the post-and-core design (298.29 MPa). It also had lower shear stress at the cement interface and reduced stress on abutment teeth. Conclusion: Endocrown-retained FPDs provide better stress distribution and structural integrity, offering a reliable, minimally invasive option for restoring endodontically treated molars. Clinical Significance: Endocrown retained 3-unit fixed partial denture can be a promising alternative to the fiber-post retained FPD for restoring molars with extensive tooth loss.

Investigation on rheological performance of indigenously developed sustainable low clinker hybrid cementing binders

Cement production is a chief source of greenhouse gas emissions and is responsible for 5–8 % of anthropogenic CO2 emissions to the atmosphere worldwide. Incorporating Supplementary cementitious materials (SCMs) into cement production can lessen the need for parent materials and also reduce about 30 % of carbon dioxide (CO2) footprint. This study examines the rheological performance of the indigenously developed low-clinker hybrid cementing binders. The rheological behavior of blends could vary with different factors like the quantity of cement replacement, the type of mineral additive, the water-to-binder ratio, and the age of the paste. The rheological performance was learned through flow curves, constant shear rate, and small amplitude oscillatory shear tests. The results obtained from samples revealed that the binary blended (BB) mix exhibited higher shear stress, and the ternary (TB) and quaternary blends (QB) exposed low shear stress. From the analysis, the dynamic yield stress was increased by increasing the SCM proportion. Constant shear rate test results showed that the BB has the highest static yield stress, then other blends. Samples showed significant elasticity and linear viscoelasticity region. The resulting compressive strength of 28 days of curing showed that the quaternary mix QB1 had the highest ultimate compressive strength (52 MPa) increased by 101.9 %. While the BB has shown the least strength (80.3 %) among other blends. The characterization studies were opted to identify the properties of SCMs. The morphological study was conducted to recognize the effect of SCMs leading to the formation of denser structures to enhance compressive strength.