SEARCH · PubMed Health

Results for “Elastic Modulus”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources

PubMed1986

Modulus of elasticity in bending of composites and amalgams.

In this study, the modulus of elasticity in bending (a measure of rigidity) and transverse strength (a measure of edge strength) were determined for composites and amalgams. the results were as follows. The modulus of elasticity of microfilled composites is approximately one-third that of the macrofiller-containing composites. Composites containing a relatively coarse-sized macrofiller have a higher elastic modulus than those containing a finer macrofiller. The transverse strength of microfilled composites is approximately one half that of the macrofiller-containing composite, which, in turn, is close in value to the transverse strength of amalgam. High-copper amalgams are substantially more rigid than the traditional low-copper amalgams, but do not show large differences among themselves. The transverse strength among various amalgams does not appear to be related to amalgam type but does correlate to final Hg content. The modulus of elasticity of composites most likely to be used in posterior teeth is approximately one third of the modulus of elasticity of amalgam; that is, amalgams are three times more rigid.

Composite Resins↗

PubMed1995

[Determination of modulus of elasticity of human periodontal membrane].

The modulus of elasticity of periodontal membrane, as an essential parameter indicating the mechanical character of periodontal membrane, is very important in biomechanical studies (e.g. finite element stress analysis and photoelastic analysis) of dental restoration. However, determination of modulus of elasticity of human periodontal membrane has not been reported in China, and there are differences among the foreign reports. In this study, 135 periodontal samples were collected from fresh teeth and alveoli of 6 healthy adults. Drawing and compressing test were performed. The results showed that the tensile modulus of elasticity of human periodontal membrane is between 3.35 and 4.59MPa and the compress modulus of elasticity 0.5402(+/- 0.348) MPa.

Adult↗

PubMed2003

Micro-mechanical characterisation of the properties of primary tooth dentine.

OBJECTIVES: Understanding the mechanical properties of dentine is of importance as adhesive restorative materials mainly achieve their bonding to the tooth structure through dentine. The current study measures the hardness and modulus of elasticity of primary molar dentine using an Ultra-Micro-Indentation System (UMIS), which allows the dentine to remain hydrated and thus is assumed to be closer to the in vivo conditions. METHODS: Eight sound primary molar teeth were axially sectioned, embedded in resin and fine polished. Two linear arrays of indentations were done on coronal dentine, from the pulp wall to dentino-enamel junction (DEJ) parallel to the tubule direction under a force load of 25mN. RESULTS: The mean hardness and elastic modulus of the dentine nearest the pulp wall was 0.52+/-0.24 and 11.59+/-3.95GPa, respectively, which was significantly lower than those of dentine in the middle area, which was 0.85+/-0.19 and 17.06+/-3.09GPa, respectively, and the dentine nearest DEJ, which was 0.91+/-0.15 and 16.33+/-3.83GPa, respectively. There is a statistically significant linear correlation between the hardness and modulus of elasticity. CONCLUSIONS: The hardness and modulus of elasticity of dentine decreases with decreasing distance from the pulp. This is of importance to clinicians because an extension of cavity preparation towards the pulp may lead to less mechanical support for a restoration.

Biomechanical Phenomena↗

PubMed1975

The modulus of elasticity of human cortical bone: an in vivo measurement and its clinical implications.

The modulus of elasticity was derived by combining the velocity of ultrasound measurements and photon absorption (Norland-Cameron method) in human cortical bone (proximal radius) in vivo. The results compare favorably with published values of the elasticity modulus obtained in vitro. Values obtained for a heterogeneous group of patients with bone and joint complaints differed from those of normal volunteers.

Adult↗

PubMed2003

The effect of fiber reinforcement type and water storage on strength properties of a provisional fixed partial denture resin.

Fracture resistance of provisional restorations is an important clinical concern. This property is directly related to transverse strength. Strengthening of provisional fixed partial dentures may result from reinforcement with various fiber types. This study evaluated the effect of fiber type and water storage on the transverse strength of a commercially available provisional resin under two different conditions. The denture resin was reinforced with either glass or aramid fiber or no reinforcement was used. Uniform samples were made from a commercially available autopolymerizing provisional fixed partial denture resin. Sixteen bar-shaped specimens (60 x 10 x 4 mm) were reinforced with pre-treated epoxy resin-coated glass fibers, with aramid fibers, or with no fibers. Eight specimens of each group, with and without fibers, were tested after 24 h of fabrication (immediate group), and after 30-day water storage. A three-point loading test was used to measure the transverse strength, the maximal deflection, and the modulus of elasticity. The Kruskal-Wallis Analysis of Variance was used to examine differences among the three groups, and then the Mann-Whitney U Test and Wilcoxon Signed Ranks Test were applied to determine pair-wise differences. The transverse strength and the maximal deflection values in the immediate group and in the 30-day water storage group were not statistically significant. In the group tested immediately, the elasticity modulus was found to be significant (P = 0.042). In the 30-day water storage group, all the values were statistically insignificant. The highest transverse strength was displayed by the glass-reinforced resin (66.25MPa) in the immediate group. The transverse strength value was 62.04MPa for the unreinforced samples in the immediate group. All the specimens exhibited lower transverse strength with an increase in water immersion time. The transverse strength value was 61.13 MPa for the glass-reinforced resin and was 61.24 MPa for the unreinforced resin. The aramid-reinforced resin decreased from 62.29 to 58.77 MPa. The addition of fiber reinforcement enhanced the physical properties (the transverse strength, the maximal deflection, the modulus of elasticity) of the processed material over that seen with no addition of fiber. Water storage did not statistically affect the transverse strength of the provisional denture resin compared to that of the unreinforced resin. The transverse strength was lowered at water storage but it was not statistically significant. The transverse strength was enhanced by fiber addition compared to the unreinforced resin. The glass fiber was superior to the other fiber. Also the modulus of elasticity was enhanced by fiber addition compared to the unreinforced resin.

Acrylic Resins↗

PubMed1987

Finite element analysis of myocardial diastolic function using three-dimensional echocardiographic reconstructions: application of a new method for study of acute ischemia in dogs.

The effect of acute myocardial ischemia on the myocardial elastic modulus has been a matter of controversy. To evaluate this question, diastolic elastic modulus was assessed by finite element analysis of left ventricular geometry using three-dimensional echocardiographic reconstructions and right and left ventricular pressure recordings. Elastic properties were estimated before and after coronary occlusion in 6 open-chest dogs. Elastic modulus values were derived by means of a computer program that determined the global elastic modulus that best predicted the diastolic changes in left ventricular geometry. In the finite element analysis after coronary occlusion, two analyses were performed: one utilizing the control elastic modulus for all segments of the left ventricle and one in which ischemic (dyskinetic) segments were assigned a higher elastic modulus. Results showed that the control elastic modulus was a poor predictor of diastolic left ventricular expansion after coronary occlusion. The finite element analysis in which the ischemic segments were assigned a higher elastic modulus better predicted ischemic diastolic wall motion patterns. Error values (difference between predicted and actual left ventricular segmental diastolic motion) were: control, 1.9 +/- 0.3 mm (mean +/- SD), ischemia, 2.9 +/- 0.5 mm, and 2.2 +/- 0.4 mm using the stiffer elastic modulus for ischemic segments. Error values were significantly higher (p less than 0.05) under ischemic conditions when the control elastic modulus was uniformly applied compared with control and ischemia with dyskinetic segments assigned a higher elastic modulus. From these data, it is concluded that the myocardial diastolic elastic modulus is increased by ischemia and that this approach may allow clinical assessment of intrinsic muscle stiffness.

Animals↗

PubMed1977

Reduction in the modulus of elasticity in orthodontic wires.

The modulus of elasticity of stainless steel orthodontic wires was found to be 20% below the normally assumed range of 19.3 to 20.0 x 10(4) MPa (28.0 to 29.0 x 10(6) psi). Use of the latter value can result in significant computational errors in orthodontic applicance mechanics. The lower modulus was attributed to severe cold drawing.

Crystallography↗

PubMed1999

Arterial stiffness and the development of hypertension. The ARIC study.

Decreased elasticity in large and medium-sized arteries has been postulated to be associated with cardiovascular diseases. We prospectively examined the relation between arterial elasticity and the development of hypertension over 6 years of follow-up in a cohort of 6992 normotensive men and women aged 45 to 64 years at baseline from the biracial, population-based Atherosclerosis Risk in Communities (ARIC) Study. Arterial elasticity was measured from high-resolution B-mode ultrasound examination of the left common carotid artery as adjusted arterial diameter change (in micrometers, simultaneously adjusted for diastolic blood pressure, pulse pressure, pulse pressure squared, diastolic arterial diameter, and height), Peterson's elastic modulus (in kilopascals), Young's elastic modulus (in kilopascals), and beta stiffness index. Incident hypertension (n=551) was defined as systolic blood pressure >/=160 mm Hg, diastolic blood pressure >/=95 mm Hg, or the use of antihypertensive medication at a follow-up examination conducted every 3 years. The age-, ethnicity-, center-, gender-, education-, smoking-, heart rate-, and obesity-adjusted means (SE) of baseline adjusted arterial diameter change, Peterson's elastic modulus, Young's elastic modulus, and beta stiffness index were 397 (5), 148 (2.0), 787 (12.7), and 11.43 (0.16), respectively, in persons who developed hypertension during follow-up, in contrast to 407 (1), 124 (0.6), 681 (3.7), and 10.34 (0.05), respectively, for persons who did not. The similarly adjusted cumulative incident rates of hypertension from the highest to the lowest quartiles of arterial elasticity were 6.7%, 8.0%, 7.3%, and 9.6%, respectively, when measured by adjusted arterial diameter change (P<0.01). One standard deviation decrease in arterial elasticity was associated with 15% greater risk of hypertension, independent of established risk factors for hypertension and the level of baseline blood pressure. These results suggest that lower arterial elasticity is related to the development of hypertension.

Age Factors↗

PubMed1994

Muscle sound frequencies of the frog are modulated by skeletal muscle tension.

The purpose of this study was to determine the relationships among muscle sound frequencies, muscle tension, and stiffness. Time-frequency transformations of nonstationary acoustic signals provided measures of resonant frequency during isometric contractions of frog (Rana pipiens) semitendinosus and gastrocnemius muscles. A mathematical expression for muscle transverse resonant frequency, elastic modulus and tension, based on elastic beam theory, was formulated by the Rayleigh method adapted for muscles. For thin muscles, the elastic modulus was found to have negligible influence on transverse muscle resonant frequency. Changes in muscle tension were the major determinants of changes in transverse resonant frequency. Consequently, for thin muscles, the time course of muscle tension, but not elastic modulus, can be monitored acoustically during the early phase of contraction when muscles give rise to sounds. Muscles were found to be anisotropic with a modulus of elasticity, EL, measured via length perturbations near 0.1% muscle length peak-to-peak, that was much larger than the modulus of elasticity, Eb, that resists the lateral bending that causes sound production. The elastic and resonant behavior of a thin muscle is similar to a tensioned fibrous cable with distributed mass.

Acoustics↗

PubMed1999

Measurements of mechanical properties of the blastula wall reveal which hypothesized mechanisms of primary invagination are physically plausible in the sea urchin Strongylocentrotus purpuratus.

Computer simulations showed that the elastic modulus of the cell layer relative to the elastic modulus of the extracellular layers predicted the effectiveness of different force-generating mechanisms for sea urchin primary invagination [L. A. Davidson, M. A. R. Koehl, R. Keller, and G. F. Oster (1995) Development 121, 2005-2018]. Here, we measured the composite elastic modulus of the cellular and extracellular matrix layers in the blastula wall of Strongylocentrotus purpuratus embryos at the mesenchyme blastula stage. Combined, these two layers exhibit a viscoelastic response with an initial stiffness ranging from 600 to 2300 Pa. To identify the cellular structures responsible for this stiffness we disrupted these structures and correlated the resulting lesions to changes in the elastic modulus. We treated embryos with cytochalasin D to disrupt the actin-based cytoskeleton, nocodazole to disrupt the microtubule-based cytoskeleton, and a gentle glycine extraction to disrupt the apical extracellular matrix (ECM). Embryos treated less than 60 min in cytochalasin D showed no change in their time-dependent elastic modulus even though F-actin was severely disrupted. Similarly, nocodazole had no effect on the elastic modulus even as the microtubules were severely disrupted. However, glycine extraction resulted in a 40 to 50% decrease in the elastic modulus along with a dramatic reduction in the hyalin protein at the apical ECM, thus implicating the apical ECM as a major mechanical component of the blastula wall. This finding bears on the mechanical plausibility of several models for primary invagination.

Actins↗

PubMed1968

Elastic-mathematical theory of cells and mitochondria in swelling process. II. Effect of temperature upon modulus of elasticity of membranous material of egg cells of sea urchin, Strongylocentrotus purpuratus, and of oyster, Crassostrea virginica.

The elastic behavior of the cell wall as a function of the temperature has been studied with particular attention being given to the swelling of egg cells of Strongylocentrotus purpuratus and Crassostrea virginica in different sea water concentrations at different temperatures. It was found that the modulus of elasticity is a nonlinear function of temperature. At about 12-13 degrees C the modulus of elasticity (E) is constant, independent of the stress (sigma) and strain (epsilon(nu)) which exist at the cell wall; the membranous material follows Hooke's law, and E approximately 3 x 10(7) dyn/cm(2) for S. purpuratus and C. virginica. When the temperature is higher or lower than 12-13 degrees C, the modulus of elasticity increases, and the membranous material does not follow Hooke's law, but is almost directly proportional to the stresses existing at the cell wall. On increasing the stress, the function E(sigma) = E(sigma) approaches saturation. The corresponding stress-strain diagrams, sigma = sigma(epsilon(nu)), and the graphs, E(sigma) = E(sigma) and E(sigma) = E(t) are given. The cyto-elastic phenomena at the membrane are discussed.

Animals↗

PubMedDate not supplied

Determinants of vascular hemodynamic characteristics.

This discussion concerns some of the parameters affecting the hemodynamic characteristics of a blood vessel: impedance, flow resistance, and vascular wall stiffness. The parameters of greatest importance are the vessel internal radius (ri) and the elastic modulus of the vascular wall. When the smooth muscle cells in the vascular wall are inactive, the elastic modulus is determined by the combined elastic modulus of the structural components of the connective tissue, primarily elastin and collagen fibers. This combined elastic modulus is found to be proportional to the wall stress. From the proportionality factor and from knowledge of the vessel dimensions in the unpressurized vessel, one can predict the relation of ri to transmural pressure. When a vessel is activated under isometric conditions, the wall force and elastic modulus are increased by the force and elastic modulus of the smooth muscle cells. Under isobaric conditions, however, the effect of activation is to reduce both the ri and the elastic modulus. Pathologic changes resulting either in a stiffening of the connective tissue components, in an increased wall cross-sectional area, which encroaches on the lumen, or in an increased smooth muscle quantity will all cause increases in vascular characteristic impedance, vascular flow resistance, and vascular wall stiffness.

Blood Vessels↗

PubMed1981

The structure of the lens epithelium and its basement membrane in the diabetic state.

The basement membrane of the crystalline lens of the diabetic rat was found to have a similar elasticity modulus at high stress to that of normal membrane. However, at low stress and extension Young's modulus of elasticity was 0.36 (Mean) +/- 0.15 (SD) X 10(6) Nm-2 and about 30 per cent lower than that of normal membrane. Diabetic membrane was significantly more extensible since it extended a further 7.5% as compared with normal membrane before it ruptured. These changes in the elastic properties of the membrane was accompanied by characteristic changes in the epithelial cells. The cells become round and swollen containing cytoplasm rich in rough and smooth endoplasmic reticulum. The changes suggest increased metabolic activity while the presence of intra-cellular membrane whorls indicate phagocytic activity. Plaques of epithelial cells were sometimes found at the anterior poles of diabetic lenses. Electron microscopic observations of ultrasonicated fragments of diabetic membrane showed that the filaments had no difference in periodicity (3.7 nm) from those found in normal membrane, but their spacing was significantly increased by 0.2 nm. The increased extensibility and decreased Young's modulus of elasticity at low stress, together with the increase spacing of the filaments, were shown to be consistent with the view that the helical macromolecules forming the filaments of diabetic basement membrane may be increased in length.

Animals↗

PubMedDate not supplied

Mechanical remodeling of small-intestine submucosa small-diameter vascular grafts--a preliminary report.

Small-intestine submucosa (SIS) is cell-free, 100-mu-thick collagen derived from the small intestine. It has been used as a vascular graft and has the highly desirable ability to be remodeled to become histologically indistinguishable from native adjacent artery. To date there has been limited reporting of its preimplantation and explant mechanical properties as a vascular graft. In this study, compliance, elastic modulus, and burst pressure were measured on preimplant-tested 5- and 8-mm SIS grafts and two 60-day remodeled grafts. Seven prefabricated grafts were implanted in the carotid (n = 7) in dogs, which were sacrificed after 55-63 days. The animals (n = 4) weighed from 22 to 27 kg. One dog received a unilateral carotid graft, and 3 dogs received bilateral carotid grafts. The fabrication technique employed hand-suturing with either nonresorbable or resorbable sutures. None of the grafts had a patency failure. Angiograms taken at 1 month and just before explantation showed uniform flow and no dilation. At the time of explantation, all carotid grafts were found to be encased in fibrous tissue. The grafts made with nonresorbable sutures showed thicker tissue growth at the suture line compared with those made with the resorbable sutures. Along the suture line, the grafts made with resorbable sutures exhibited a more natural color than those sutured with nonresorbable sutures. When the explanted carotid grafts were slit open, the lumen was white, shiny, and glistening. The grafts sutured with nonresorbable sutures exhibited small areas of fibrin and red blood cells when the suture was within the lumen. The resorbable-sutured grafts did not exhibit this response. The mean compliance (percent diameter increase for a pressure rise from 80 to 120 mm Hg) was on average 4.6% (range, 2.9%-8.6%) for the 5-mm preimplant-tested grafts. For the 8-mm preimplant-tested grafts, the increase in diameter for the same pressure rise was 8.7%, on average (range, 7.2% to 9.5%). For comparison, the small-diameter SIS graft at the time of implantation was about one half as compliant as the adjacent dog carotid artery, about 4 times more compliant than a typical vein graft, and more than 10 times more compliant than synthetic vascular grafts. The compliance measured on two 60-day carotid grafts was 10.5% and 7.2%, respectively. This is midway between the original compliance value and the compliance of a typical canine carotid artery (14%), indicating that mechanical remodeling occurred. The modulus of elasticity (E) increased exponentially with increasing pressure according to E = E0e alpha P, where E0 is the zero-pressure modulus and alpha is the exponent that describes the rate of increase in E with pressure; the unit of measure for variables E, E0, and P is g/cm2. The mean value for E0 was 4106 gm/cm2 (range, 1348-5601). The mean value for alpha was 0.0059 (range, 0.0028-0.0125). At 100 mm Hg, the mean value for E was 8.03 x 10(6) dynes/cm2 (range, 4.95-15.7 x 10(6)). For a 60-day SIS graft implant, the elastic modulus at 100 mm Hg decreased from a high value at implant time to twice that of a typical native canine carotid artery. The mean burst pressure for 5.5-mm grafts was 3517 mm Hg (range, 2069-4654). The burst pressure of the remodeled carotid grafts averaged 5660 mm Hg. The burst pressure for a typical carotid artery is about 5000 mm Hg. The results of this preliminary study complement those of previous SIS-vascular-graft studies and add a new factor, namely that the mechanical properties of the remodeled graft approach those of the vessel it replaces.

Animals↗

PubMed1993

Effects of femoral component material properties on cementless fixation in total hip arthroplasty. A comparison study between carbon composite, titanium alloy, and stainless steel.

Carbon-fiber-reinforced-carbon composite material is an attractive implant material because its modulus of elasticity can be made similar to that of cortical bone. This study investigated the effect of femoral prosthesis elastic modulus on cementless implant fixation. Distal, as well as proximal, relative micromovements between implant and bone were measured in two testing protocols (axial-load and torsional-load), comparing identically shaped carbon composite (modulus of elasticity = 18.6 GPa), Ti6Al4V (100 GPa), and 630 stainless steel (200 GPa) prostheses. In the axial-load test, proximal mediolateral micromotions were significantly larger in the flexible composite stem than in the two metals. In the torsional-load test, rotational micromotions and "slop" displacements in the flexible stem were significantly larger proximally and significantly smaller distally than in the two metals. While these results suggest that proximal stress transfer may be improved by a flexible stem, they raise the possibility of increased proximal micromotion, and suggest that improved proximal fixation may be necessary to achieve clinical success with flexible composite femoral components.

Alloys↗

PubMed2005

Change of mechanical properties during short-term natural weathering of MSWI bottom ash.

The present work describes the change of mechanical properties during the natural weathering of freshly quenched processed bottom ash. An unconfined uniaxial compression to failure test of the unbound material was used to determine compressive strength and modulus of elasticity. Three main stages of mechanical behavior were determined. In the first stage, during a period lower than 30 days, mechanical properties suddenly increase, with a compressive strength and elastic modulus 7 times greater than the initial parameters. During the second stage, compressive strength and modulus of elasticity lightly increase until approximately 90 days of curing time. Starting from this period both mechanical properties remain steady and independent of the curing time. The neoformed phases, the elevated water content, and the improvement of particle contact after compaction act as a binder layer among particles, increasing the mechanical parameters during the short-term natural weathering process. Because of this, the freshly compacted bottom ash progresses from behaving as an unbound material into a bound pavement material. These mechanical properties obtained from freshly quenched bottom ash are 6-7 times greater than those obtained from previously weathered bottom ash. The bottom ash expansion and leaching of metals were also evaluated.

Construction Materials↗

PubMed2005

The effects of prolonged ethanol exposure on the mechanical properties of polyurethane and silicone catheters used for intravascular access.

BACKGROUND: Products containing alcohol are commonly used with intravascular devices at insertion, to remove lipids from occluded intravascular devices used during parenteral nutrition, and increasingly for the prevention and treatment of intravascular device-related bloodstream infection. The effects of alcohol on the integrity of intravascular devices remain unknown. METHODS: Two types of widely used commercial peripherally inserted central catheters, one made of polyetherurethane and one made of silicone, were exposed to a 70% ethanol lock solution for up to 10 weeks. Mechanical testing was performed to identify force-at-break, stress, strain, modulus of elasticity, modulus of toughness, and wall area of ethanol-exposed and control catheters. RESULTS: No significant differences between exposed and unexposed catheters were identified for any of the mechanical parameters tested except for a marginal reduction in the modulus of elasticity for both polyetherurethane and silicone catheters and minor increases in the wall area of polyetherurethane catheters. CONCLUSIONS: These data indicate that exposure to a 70% ethanol lock solution does not appreciably alter the integrity of selected commercial polyetherurethane and silicone catheters. Given the greatly expanded use of alcoholic solutions with intravascular devices of all types, we believe that manufacturers would be well advised to subject their catheters and other intravascular devices to formal testing of the type employed in this study.

Catheterization↗

PubMed1992

Compressive mechanical properties of human cancellous bone after gamma irradiation.

The effect of gamma irradiation on the mechanical properties of human bone was examined. Specimens of cancellous bone were cut from the proximal epiphyseal region of fresh-frozen tibiae and divided into control and irradiated groups according to anatomical region. The irradiated groups were exposed to 10,000, 31,000, 51,000, or 60,000 gray (1.0, 3.1, 5.1, or 6.0 megarad). The specimens were tested in compression to failure to determine failure stress, strain to failure, and elastic modulus. Failure stress and elastic modulus were found to be proportional to the square of the density and were normalized with respect to this property. Significant differences in normalized failure stress (p less than 0.001) and normalized elastic modulus (p = 0.003), when compared with the values for matched control specimens, were found only for the specimens that had been irradiated with 60,000 gray (6.0 megarad).

Aged↗