Influence Of Compression Force Research Articles

Influence of compressive forces and aging through thermocycling on the strength of mono incremental dental composite resins

Understanding dental composite resins' physical and mechanical properties is vital for advancing dental materials science, enhancing durability, and improving patient care. The present study aims to quantitatively investigate the impact of compressive forces and thermocycling aging on the strength of mono incremental dental composite resins, focusing on three materials: 3M Filtek One Bulk Fill, Opus Bulk Fill APS A2 from FGM, and Tetric N-Ceram Bulk Fill VIA from Ivoclar Vivadent. Using a mixed quasi-experimental approach, 84 samples were divided into a control group and an experimental group, comprising 14 samples of each material. The samples underwent a thermocycling process involving temperature cycles between 5°C, 37°C, and 55°C, totaling 10,800 cycles, simulating one year of aging. Subsequently, compressive strength tests were conducted using a universal press to identify the fracture point of the material and calculate its strength. Our results reveal differences in the material before and after thermocycling; however, these differences were not statistically significant concerning strength. Thus, it is concluded that one year of thermocycling aging does not induce substantial changes in the resin that would compromise its strength. Future research should consider extended thermocycling tests spanning multiple years to pinpoint the potential onset of issues affecting material strength durability. Keywords: compressive strength, dental composite resins, thermocycling, aging, mono incremental.

Immunorthodontics: Role of HIF-1α in the Regulation of (Peptidoglycan-Induced) PD-L1 Expression in Cementoblasts under Compressive Force.

Patients with periodontitis undergoing orthodontic therapy may suffer from undesired dental root resorption. The purpose of this in vitro study was to investigate the molecular mechanisms resulting in PD-L1 expression of cementoblasts in response to infection with Porphyromonas gingivalis (P. gingivalis) peptidoglycan (PGN) and compressive force (CF), and its interaction with hypoxia-inducible factor (HIF)-1α molecule: The cementoblast (OCCM-30) cells were kinetically infected with various concentrations of P. gingivalis PGN in the presence and absence of CF. Western blotting and RT-qPCR were performed to examine the protein expression of PD-L1 and HIF-1α as well as their gene expression. Immunofluorescence was applied to visualize the localization of these proteins within cells. An HIF-1α inhibitor was added for further investigation of necroptosis by flow cytometry analysis. Releases of soluble GAS-6 were measured by ELISA. P. gingivalis PGN dose dependently stimulated PD-L1 upregulation in cementoblasts at protein and mRNA levels. CF combined with P. gingivalis PGN had synergistic effects on the induction of PD-L1. Blockade of HIF-1α inhibited the P. gingivalis PGN-inducible PD-L1 protein expression under compression, indicating an HIF-1α dependent regulation of PD-L1 induction. Concomitantly, an HIF-1α inhibitor decreased the GAS-6 release in the presence of CF and P. gingivalis PGN co-stimulation. The data suggest that PGN of P. gingivalis participates in PD-L1 up-regulation in cementoblasts. Additionally, the influence of compressive force on P. gingivalis PGN-induced PD-L1 expression occurs in HIF-1α dependently. In this regard, HIF-1α may play roles in the immune response of cementoblasts via immune-inhibitory PD-L1. Our results underline the importance of molecular mechanisms involved in bacteria-induced periodontics and root resorption.

Spray-Dried Paracetamol/Polyvinylpyrrolidone Amorphous Solid Dispersions: Part I-Stability of Powders and Tablets.

The formulation of active pharmaceutical ingredients (APIs) in amorphous solid dispersions (ASDs) is a promising approach to improve the bioavailability of poorly soluble compounds. However, problems often arise in the production of tablets from ASDs regarding the compressibility and recrystallization of the API. In the present study, the preparation of spray-dried ASDs of paracetamol (PCM) and four different types of polyvinylpyrrolidone (PVP) and their further processing into tablets were investigated. The influence of PVP type on the glass transition temperature (Tg) and the physical stability of ASD powders were characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD). ASD powders with 10 to 30% PCM were stable for at least 48 weeks. PCM contents of 40 to 50% led to recrystallization of the amorphous PCM within a few days or weeks. ASD with PVP/vinyl acetate (VA) copolymer (PVP/VA) was the most unstable and tended to recrystallize in PCM polymorphic form II. This formulation was therefore used for tablet studies. The influence of compression force on recrystallization, crushing strength, and drug release was investigated. Even high compression forces did not affect the stability of the ASD. However, the ASD tablets led to slow release of the API.

Contact characteristics of steel-rubber rollers based on modified contact theory considering viscoelasticity

This paper mainly studied the contact characteristics of steel-rubber rollers. First, according to the dynamic mechanical experimental data of rubber, the hyperelastic-viscoelastic composite constitutive model was constructed to accurately describe the properties of rubber. Then, for the contact problem of steel-rubber rollers, the elastic modulus of rubber presents an instantaneous change due to the influence of rubber's viscoelasticity, so the Hertz contact theory was modified through the instantaneous elastic modulus. Next, a dimensionless parameter [Formula: see text] was constructed to judge the viscoelastic influence degree of rubber. Finally, based on modified contact theory and the dimensionless parameter [Formula: see text], the influence of compressive force and rolling speed on the contact characteristics of steel-rubber rollers was analyzed. The research in this paper is helpful to the analysis of dynamic contact problem of rollers structure and the development of contact theory.

Application of nonlinear impedance spectroscopy for the diagnosis of lithium-ion battery cells under various operating conditions

Nonlinear impedance spectroscopy is a novel method for the diagnosis of lithium-ion battery cells. To thoroughly evaluate the application of nonlinear impedance measurements within this contribution, the topic is theoretically investigated at first. The ordinary frequency response function is extended to the Volterra model to incorporate nonlinear behavior. The applied data-driven approach simplifies the assessment of nonlinear distortions based on Fourier transforms. To experimentally analyze the frequency response of battery cells in a defined manner, a measurement setup is constructed that features a mechanical clamping device. Next to controlling the temperature and the state of charge (SoC), the force compressing the cell can be specifically adjusted with this test rig. Thereby, the influence of compressive force on the impedance spectrum and its harmonic content is examined. In addition, it is analyzed if and how the mechanical influence can be distinguished with nonlinear impedance spectroscopy from other impedance-changing conditions such as temperature and SoC. The investigation based on pouch battery cells results in diverse diagnostic scenarios, where nonlinear impedance measurements are a valuable extension to traditional battery characterization tools. The comparison is complemented by evaluating drawbacks of the method and the impact of the measurement procedure on the device under test.

Study of the influence of compressive force on the coefficients of friction for wool-containing fabrics

Making use of appliance MXD-02, Labthink, China, coefficient of friction at rest with sliding tendency (static coefficient of friction) and coefficient of friction at sliding (dynamic coefficient of friction) for fabrics made of 100% wool as well as woolen fabrics with admixtures of polyamide and polyester were determined. The influence of the magnitude of normal pressure on the coefficients of friction was studied. Experiments taking into consideration the following different directions of relative fabric movement were performed: warp by warp threads, and warp by weft. An analysis of the obtained results was made.

Influence of compressive force in floating plate on its deflections at the unsteady body motion in liquid

The three-dimensional unsteady problem of the movement of a thin body in liquid under a floating plate is solved. The effect of lateral stress of the plate on its deflections and a slope of the curved surface is analyzed. It is received that compression (stretch) of the plate leads to the decreasing (increasing) of critical speeds. The wave height reaches the greatest values for the stretched plate. At supercritical compression of the plate the wave height grows rapidly and breaking occurs.

The influence of compressive forces across the patellofemoral joint on patient-reported outcome after bi-cruciate stabilized total knee arthroplasty.

Patellofemoral problems are a common complication of total knee arthroplasty. A high compressive force across the patellofemoral joint may affect patient-reported outcome. However, the relationship between patient-reported outcome and the intraoperative patellofemoral contact force has not been investigated. The purpose of this study was to determine whether or not a high intraoperative patellofemoral compressive force affects patient-reported outcome. This prospective study included 42 patients (42 knees) with varus-type osteoarthritis who underwent a bi-cruciate stabilized total knee arthroplasty and in whom the planned alignment was confirmed on 3D CT. Of the 42 patients, 36 were women and six were men. Their mean age was 72.3 years (61 to 87) and their mean body mass index (BMI) was 24.4 kg/m 2 (18.2 to 34.3). After implantation of the femoral and tibial components, the compressive force across the patellofemoral joint was measured at 10°, 30°, 60°, 90°, 120°, and 140° of flexion using a load cell (Kyowa Electronic Instruments Co., Ltd., Tokyo, Japan) manufactured in the same shape as the patellar implant. Multiple regression analyses were conducted to investigate the relationship between intraoperative patellofemoral compressive force and patient-reported outcome two years after implantation. No patient had anterior knee pain after total knee arthroplasty. The compressive force across the patellofemoral joint at 140°of flexion was negatively correlated with patient satisfaction (R 2 = 0.458; β = -0.706; p = 0. 041) and Forgotten Joint Score-12 (FJS-12; R 2 = .378; β = -0.636; p = 0. 036). The compressive force across the patellofemoral joint at 60° of flexion was negatively correlated with the patella score (R 2 = 0.417; β = -0.688; p = 0. 046). Patient satisfaction, FJS-12, and patella score were affected by the patellofemoral compressive force at 60° and 140° of flexion. Reduction of the patellofemoral compressive forces at 60° and 140° of flexion angle during total knee arthroplasty may improve patient-reported outcome, but has no effect on anterior knee pain.

Analytical linear modelization of a buckled undulating membrane tidal energy converter

This paper presents an analytical linear model developed to study the behaviour of a buckled membrane tidal energy converter. The Euler beam theory and the elongated body theory are used for the fluid structure interaction formulation. The effect of electromechanical converters used to convert the undulating motion into electrical energy is reproduced by adding a term equivalent to viscous material damping. The influence of compression force, flaps and hanging conditions is studied, as well as the effects of simulated power take-off through internal damping. The system's behaviour is characterized by undulating mode, critical flow velocity, motion frequency and amplitude. The model shows good agreement in terms of frequency and satisfactory results for the amplitude compared to experimental data. The linear assumptions were validated on fluid and structure models as a good start for a first analytical model describing the system's physic. The obtained results confirmed the benefits of initial stress and optimized damping to the tidal converter for energy harnessing. • The behaviour of an undulating membrane tidal energy convertor has been modelized. • The model is linearized to enable light computation. • Results of frequency, trajectory and hydrodynamic forces fit the experiments. • Optimization of the tidal energy collected is discussed.

The Milky Way: paediatric milk-based dispersible tablets prepared by direct compression - a proof-of-concept study.

Dispersible tablets are proposed by the World Health Organization as the preferred paediatric formulation. It was hypothesised that tablets made from a powdered milk-base that disperse in water to form suspensions resembling milk might be a useful platform to improve acceptability in children. Milk-based dispersible tablets containing various types of powdered milk and infant formulae were formulated. The influence of milk type and content on placebo tablet properties was investigated using a design-of-experiments approach. Responses measured included friability, crushing strength and disintegration time. Additionally, the influence of compression force on the tablet properties of a model formulation was studied by compaction simulation. Disintegration times increased as milk content increased. Compaction simulation studies showed that compression force influenced disintegration time. These results suggest that the milk content, rather than type, and compression force were the most important determinants of disintegration. Up to 30% milk could be incorporated to produce 200 mg 10-mm flat-faced placebo tablets by direct compression disintegrating within 3 min in 5-10 ml of water, which is a realistic administration volume in children. The platform could accommodate 30% of a model active pharmaceutical ingredient (caffeine citrate).

The paradox of Wolff’s theories

The upper femur has long held a fascination for both clinicians and bioengineers as it contains two trabecular columns obviously related to its function. In this respect two theories as to the formation of these columns have developed, both associated with Wolff: the Trajectorial Theory, which relates mainly to the passage of forces through the cancellous bone of the upper femur, and Wolff's Law of bone formation, which describes the bone's reaction to these forces and relates to bone in general. The two concepts nevertheless are often used synonymously. The Trajectorial Theory propounds that these cancellous structures in the femoral neck are due to both tension and compression forces, while modern day concepts of Wolff's Law only acknowledge the action of compression forces: and herein lies the paradox. The Trajectorial Theory and Wolff's Law, when applied to the upper femur, are mutually exclusive. The evidence, anatomical and physiological, indicates that bone forms within the femoral neck solely under the influence of compression forces. This would indicate that the Trajectorial Theory is not appropriate for this region. An alternative conceptual way of looking at this region is presented which eliminates this theory and resolves the paradox.

Development of a Discriminative Intrinsic Dissolution Method for Efavirenz

Efavirenz is a poorly water-soluble drug categorized as a Class 2 drug under the Biopharmaceutics Classification System (BCS). Intrinsic dissolution is an effective tool for evaluating the physical–chemical properties of an active pharmaceutical ingredient (API). The aim of this study was to develop an intrinsic dissolution method for use in quality control of efavirenz to be used in the selection of an API for the production of dosage forms. The influence of compression force, rotation speed, dissolution medium, and surfactant concentration on the intrinsic dissolution rate (IDR) of efavirenz were evaluated using a rotating-disk holder. The developed method was applied to the evaluation of batches using different raw materials (batches A–G). Dissolution media containing 0.5% sodium lauryl sulfate (SLS) and a rotation speed of 100 rpm proved the most discriminative. Batches A, D, and F provided intrinsic dissolution rate (IDR) values greater than 36 μg/min/cm2 in this medium, while batches B and E provided IDR values of approximately 31 μg/min/cm2. The IDRs obtained showed a high correlation with the surface areas of the batches. The method may be used in the development of efavirenz formulations to select API with physical–chemical properties that enable appropriate dosage form dissolution.

Squeezing Impact Forces of the Deformation on a Cylindrical Roller

The article examines the influence of compressive forces on the deformation of the cylindrical roller. We considered the features of deformation of two cylindrical bodies with identical elastic properties and elastic plastic deformation of the deforming element of the solid parts. Duing the process we calculated deformation of the cylindrical deforming element which is located between the two contracting rigid planar faces of it with a light contact and general deformations. It is shown that the relative deformation of the reels when they are loading does not depend much on the diameter, but depends only on the loading force. It’s produced by computer simulation of compression of a cylindrical roller with two absolutely rigid plates using the software like Pro/E, Solidworks and ANSYS. We obtain the results of experimental investigations of the deformation roller during its compression of flat plates with a hardness of HRC = 65. It was revealed that the deformation roller obtained experimentally is almost identical with the calculated values. It is shown that deformation of the roller shall not exceed two percent of its diameter, and in the calculations determining the parameters of the contact zone can not take into account its deformation.

Understanding Disintegrant Action by Visualization

The aim of this study was to utilize high-speed video imaging for understanding the disintegrability of compacts and disintegrant action upon wetting. High-speed video imaging was used to visualize the disintegration of compacts and effect of wetting on free disintegrant particles. Acquired images were processed using MATLAB, and changes in the compact area and instantaneous motion of compacted particles on contact with water were analyzed. The capillary action of compacts was also determined for various disintegrants. Finally, the breakdown behavior of compacts prepared with selected disintegrants was analyzed at different compression forces to evaluate recovery of compaction strain. Water-insoluble inert diluent, dicalcium phosphate, was used as a comparator. The results from this visualization study provided an in-depth understanding of the disintegrant behavior of free and compacted disintegrant particles upon wetting. The mechanisms of swelling, capillary action, disruption of particle-particle bonds and strain recovery were successfully monitored by video imaging. The disintegration of compacts containing crospovidone appeared to be less influenced by swelling or wicking action. The influence of compression force on the disintegration of selected disintegrants confirmed that strain recovery is the dominant mechanism for the disintegrant action of crospovidone.

Influence of Compressive Force and IL-1^|^beta; on Metabolism of the Extracellular Matrix in Human Chondrocytes

Influence of Compressive Force and IL-1^|^beta; on Metabolism of the Extracellular Matrix in Human Chondrocytes

Influence of compression forces and superdisintegrants on tablets performance: comparison of biosusceptometry, water uptake and disintegration force

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Influence of Compression Force on The Behavior of Mucoadhesive Buccal Tablets

The purpose of this research was to study the compression force influence on polymers, tablet behavior and drug release rate. Several tablet batches were produced by varying the compression force and by using hydroxyethyl cellulose (HEC) and Carbopol 940 in the 1:1 ratio as matrix forming polymers. All batches were characterized by DSC and X-ray analyses and in terms of swelling, ex vivo and in vivo mucoadhesive time, ex vivo mucoadhesion force, and in vitro and in vivo release. No significant excipient-excipient or excipient-drug interactions were observed in any of the batches. All the tablets hydrated quickly and their high hydration percentage showed that the compression forces used did not remarkably affect the water penetration and the polymeric chain stretching. Mucoadhesion performances and drug release were mainly influenced by compression force; its increase produced higher ex vivo and in vivo mucoadhesion and the in vitro and in vivo drug releases were seen to decrease with the increase of the compression force. However tablets fabricated by using the lowest compression force showed the best in vivo mucoadhesive time and hydrated faster when compared to the others. Tablets 4 and 5, prepared with the highest forces, caused pain during in vivo application and gave rise to irritation needing to be detached by the volunteers while tablet 1, prepared with the lowest force, gave the best results because it was able to produce the highest drug salivary concentration and no pain. All tablets exhibited an anomalous release mechanism.

Effect of some physical parameters on the sustained drug-release properties of substituted amylose matrices

Substituted amylose (SA) matrix drug tablets prepared by direct compression show sustained drug-release properties. The influence of compression force (CF) and tablet weight (TW) on release properties was studied. CF ranging from 0.5 to 5.0 tons/cm 2 has no significant effect on the release properties of SA,G (glycidol) polymers, with a degree of substitution (DS) greater than 1.5. For a low DS, an augmentation of CF increases the release time of acetaminophen, used as a model drug, until a certain limit is reached. On the other hand, TW has a major effect on the release time of acetaminophen. Release time is directly proportional to TW. The effect of the nature of the active material, its solubility and its concentration in the formulation on the release properties of SA,G polymers was also evaluated, demonstrating the versatility of the system.

Effect of some physical parameters on the swelling properties of cross-linked amylose matrices

The influence of compression force (CF) on initial tablet porosity and water uptake kinetics in cross-linked amylose (CLA) matrices was determined by mercury intrusion and gravimetry, respectively. Major changes in tablet porosity and pore size distribution occurred in the CF range of 1–5 T with little or no effect on the gelation properties of CLA matrices. Compression properties of CLA tablets were also characterized by electron scanning microscopy. The presence of macrovoids within micro- or non-porous regions was observed. This may reflect a certain fragmentation taking place in addition to plastic deformation during compression. The effect of pH, ionic strength and osmolarity of the medium on the uptake properties of CLA tablets was also evaluated. Although the swelling profiles of CLA matrices were found to be independent of pH (1.4–8) and of medium osmolarity (0–0.1 M sucrose solutions), a significant drop in the swelling capacity of tablets was observed with increased NaCl concentration. This decrease—not related to ionic interactions—may be due to changes in the gelation properties of the polymer.

Effects of Compression Force and Type of Fillers on Release of Diclofenac Sodium from Matrix Tablets

AbstractThe influence of compression force and type of fillers on the release pattern of diclofenac sodium from wet-granulated tablet matrices containing Emcompress and lactose as fillers with Eudragit RSPM as a matrix additive was determined. The release pattern of diclofenac sodium from these matrices in USP phosphate buffer pH 7.2 at 37 ° C were found to be independent of compression forces whereas the ratios of insoluble (Emcompress) to soluble filler (lactose) appeared to greatly influence the drug release rate as evidenced in the increased release rate with decreasing Emcompress content. The kinetics of drug release was determined and found to precisely comform to the Higuchi's planar matrix model. A theoretical approach to predict the drug release rate from a designed system was presented and found to be satisfactorily predictive.