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PubMed2006

In vitro properties' changes of latex and non-latex orthodontic elastics.

OBJECTIVES: The purpose of this study is to evaluate the effectiveness of non-latex elastics regarding their use in clinical practice for latex-intolerant individuals. MATERIALS AND METHODS: In this study, 80 latex and 80 non-latex elastics produced by Leone S.p.A. were divided into 4 groups of 20 elastics each. They were submitted to traction tests after being placed in Ringer's solution for different periods of time. Force loss and permanent deformation (considered as the difference between the initial and final diameter) was then determined in order to evaluate the behaviour of each elastic after every test. The variation of force was calculated using the Instron Machine, while the profile projector was used to measure the elastics' diameter. RESULTS: The latex elastics undergo less loss of force than the non latex elastics. The difference between the two tested samples becomes significant after 24 hours. Regarding the variation of the inner diameter, in every test, non-latex elastics showed a more significant deformation than latex ones and the difference was significant. CONCLUSION: When compared to latex elastics, non-latex elastics showed a greater deformation of the inner diameter and the forces generated in Ringer's solution are significantly less after 24 hours. To conclude, latex-free elastics are suitable for orthodontic treatment in patients with allergies, although further study to investigate the dynamic behaviour of latex- free elastics.

Dental Materials↗
PubMed1983

Elastic fibres of the human ductus deferens.

The distribution of elastic fibres in the human ductus deferens from birth to senility was studied by light and electron microscopy. Elastic fibres are lacking in the ductus deferens in infants and children. In the adult ductus deferens, they form two layers in the lamina propria: (1) an inner layer of circumferentially oriented elastic fibres, and (2) an outer meshwork of elastic fibres. Elastic fibres are also present in the narrow intercellular spaces between the smooth muscle cells of the muscular coat, mainly in the inner muscular layer. A layer of elastic fibres surrounds the muscular coat. The ductus deferens of ageing subjects shows fragmentation and disorganisation of the elastic fibre layers of the lamina propria. Elastic fibres in the muscular coat are more abundant than in younger adults, forming larger bundles. Electron microscopy demonstrated the presence of immature elastic fibres at puberty as collections of microfibrils, some of them containing loci of amorphous substance (elastin). In the adult ductus most elastic fibres have a mature appearance. The amount of amorphous substance has increased and the number of microfibrils has decreased. Electron-dense inclusions are present within the amorphous substance. With advancing age the amorphous substance forms large, structureless masses showing abundant electron-dense inclusions and areas of rarefaction. A thin layer of microfibrils is present only at the periphery of the elastic fibres. Whether or not androgenic hormones are in any way involved in the formation of elastic fibres in the ductus deferens and testis is something which requires further study.

Adolescent↗
PubMed2006

Consumer brand choice: individual and group analyses of demand elasticity.

Following the behavior-analytic tradition of analyzing individual behavior, the present research investigated demand elasticity of individual consumers purchasing supermarket products, and compared individual and group analyses of elasticity. Panel data from 80 UK consumers purchasing 9 product categories (i.e., baked beans, biscuits, breakfast cereals, butter, cheese, fruit juice, instant coffee, margarine and tea) during a 16-week period were used. Elasticity coefficients were calculated for individual consumers with data from all or only 1 product category (intra-consumer elasticities), and for each product category using all data points from all consumers (overall product elasticity) or 1 average data point per consumer (interconsumer elasticity). In addition to this, split-sample elasticity coefficients were obtained for each individual with data from all product categories purchased during weeks 1 to 8 and 9 to 16. The results suggest that: 1) demand elasticity coefficients calculated for individual consumers purchasing supermarket food products are compatible with predictions from economic theory and behavioral economics; 2) overall product elasticities, typically employed in marketing and econometric research, include effects of interconsumer and intraconsumer elasticities; 3) when comparing demand elasticities of different product categories, group and individual analyses yield similar trends; and 4) individual differences in demand elasticity are relatively consistent across time, but do not seem to be consistent across products. These results demonstrate the theoretical, methodological, and managerial relevance of investigating the behavior of individual consumers.

Choice Behavior↗
PubMed1984

A rapid digestive technique to expose networks of vascular elastic fibers for SEM observation.

The NaOH sonication digestion technique permits rapid isolation and exposure of intact networks of elastic fibers in vascular tissue for 3-dimensional observation with the SEM. The configuration of the network of elastic fibers within the vascular wall of large elastic arteries (aorta) is generally agreed to be a flexible framework through which smooth muscle cells and collagenous fibers are interwoven. However, the configuration of elastic fiber networks in muscular arteries, medium sized veins and smaller vessels remains unknown. When the lengthy standard biochemical elastin purification techniques were applied to vessels containing lesser amounts of elastic tissue and finer elastic fibers, the vessels were completely digested. In contrast, the digestion and sonication technique isolated and exposed intact networks of delicate elastic fibers in blood vessels which do not contain large amounts of elastic tissue. Unfixed vessels were cut into short segments, placed in 0.5 N NaOH and sonicated for 20-40 min. The specimens were rinsed in deionized distilled H2O, then autoclaved for 30 min. The tissue was rinsed a second time, fixed and processed routinely for SEM. Elastic stains and enzymatic digestion with chromatographically purified elastase and collagenase confirmed that the digestion and sonication technique produced clean, isolated networks of elastic fibers. Knowledge of the configuration of the networks of elastic fibers in different vessels enhances understanding of distensibility characteristics of individual vessels and serves as a baseline for studying alterations in the elastic framework which occur during aging and disease processes such as atherosclerosis, arterial hypertension and aneurysms.

Animals↗
PubMed1995

Three-dimensional organization of the elastic fibres in the rat lung.

BACKGROUND: The elastic framework of the distal lung has been studied by light microscopy (LM) and transmission electron microscopy (TEM). The preservation of the elastic fibres, for the three-dimensional observation in their relative positions, is difficult because they lack support when the normal methods of tissue processing are used. The goal of the present study was to understand the three-dimensional ultrastructure and organization of the elastic fibres of the lung preserved in their relative positions. METHODS: A combination of intravascular resin injection and formic acid digestion was used. The resin cast of the microvasculature acted as a scaffold to preserve the in vivo arrangement of the elastic fibres that are, otherwise, easily collapsible. Scanning electron microscopy (SEM) samples were further processed for TEM in order to confirm that the fibres were indeed components of the elastic system. RESULTS: SEM demonstrated a fine framework of elastic fibres, representing remnants of the alveolar walls, with the casted capillaries interwoven with the network of elastin. Each individual elastic fibre is composed of a small bundle of discrete fibrils. Some of these fibrils emerge from the fibre and join other fibres, producing an anastomosing appearance. Several elastic fibres link the walls of the intrapulmonary conducting airways, the vessels walls and the alveolar network, thus establishing an interrelated and interlaced framework. CONCLUSIONS: The method we have applied to visualize the elastic fibres of the lung is a unique approach to define the spatial organization of the pulmonary elastic fibres. We have demonstrated here the close relationship between the elastic fibres and the capillaries of the septal alveoli. The arrangement of the interwoven network of elastin and its relationship with the capillaries offers the structural setting for the distending capacity of the alveolar wall.

Animals↗
PubMed1993

Storage and utilization of elastic strain energy during jumping.

Based upon the optimal control solutions to a maximum-height countermovement jump (CMJ) and a maximum-height squat jump (SJ), this paper provides a quantitative description of how tendons and the elastic elements of muscle store and deliver energy during vertical jumping. After confirming the ability of the model to replicate the major features of each jump (i.e. muscle activation patterns, body-segmental motions, ground reaction forces, jump height, and total ground contact time), the time histories of the forces and shortening velocities of all the musculotendon actuators in the model were used to calculate the work done on the skeleton by tendons as well as the series-elastic elements, the parallel-elastic elements, and the contractile elements of muscle. We found that all the elastic tissues delivered nearly the same amount of energy to the skeleton during a CMJ and an SJ. The reason is twofold: first, nearly as much elastic strain energy was stored during the SJ as the CMJ; second, more stored elastic strain energy was lost as heat during the CMJ. There was also a difference in the way energy was stored during each jump. During the CMJ, strain energy stored in the elastic tissues came primarily from the gravitational potential energy of the skeleton as the more proximal extensor muscles were stretched during the downward phase of the jump. During the SJ, on the other hand, energy stored in the elastic tissues came primarily from the contractile elements as they did work to stretch the tendons and the series-elastic elements of the muscles. Increasing tendon compliance in the model led to an increase in elastic energy storage and utilization, but it also decreased the amount of energy delivered by the contractile elements to the skeleton. Jump height therefore remained almost the same for both jumps. These results suggest that elastic energy storage and utilization enhance jumping efficiency much more than overall jumping performance.

Adult↗
PubMed1999

Elasticity of vesicles affects hairless mouse skin structure and permeability.

One of the possibilities for increasing the penetration rate of drugs through the skin is the use of vesicular systems. Currently, special attention is paid to the elastic properties of liquid-state vesicles, which are supposed to have superior properties compared to gel-state vesicles with respect to skin interactions. In this study, the effects of vesicles on hairless mouse skin, both in vivo and in vitro, were studied in relation to the composition of vesicles. The interactions of elastic vesicles containing the single chain surfactant octaoxyethylene laurate-ester (PEG-8-L) and sucrose laurate-ester (L-595) with hairless mouse skin were studied, in vivo, after non-occlusive application for 1, 3 and 6 h. The skin ultrastructure was examined by ruthenium tetroxide electron microscopy (TEM) and histology. The extent, to which vesicle constituents penetrated into the stratum corneum, was quantified by thin layer chromatography (TLC). The interactions of the elastic vesicles containing PEG-8-L and L-595 surfactants were compared with those observed after treatment with rigid vesicles containing the surfactant sucrose stearate-ester (Wasag-7). Furthermore, skin permeability experiments were carried out to investigate the effect of treatment with PEG-8-L micelles, elastic vesicles (containing PEG-8-L and L-595 surfactants) or rigid Wasag-7 vesicles on the 3H(2)O transport through hairless mouse skin, in vitro, after non-occlusive application. Treatment of hairless mouse skin with the elastic vesicles affected the ultrastructure of the stratum corneum: distinct regions with lamellar stacks derived from the vesicles were observed in intercellular spaces of the stratum corneum. These stacks disrupted the organization of skin bilayers leading to an increased skin permeability, whereas no changes in the ultrastructure of the underlying viable epidermis were observed. Treatment with rigid Wasag-7 vesicles did not affect the skin ultrastructure or skin permeability. TLC measurements showed that after 1 h of non-occlusive application of elastic or rigid vesicles, a six-fold increased amount of elastic vesicle material was present within the stratum corneum compared to rigid vesicle material. After 3 and 6 h of application the amount of PEG-8-L vesicle material in SC decreased to approximately three- and two-fold, respectively, compared to Wasag-7 vesicle material. Pretreatment of the hairless mouse skin with the elastic vesicles containing 70 mol% PEG-8-L increased the diffusion of 3H(2)O with an optimum application dose of 2.5 mg lipids/cm(2) compared to PBS pretreatment. No significant difference in the enhancement of the 3H(2)O-diffusion was observed between PEG-8-L micelles or elastic vesicles containing 30 or 70 mol% PEG-8-L. Pretreatment with the rigid Wasag-7 vesicles decreased the diffusion rate of 3H(2)O, most probably by the formation of a lipid layer on the skin surface. The effect of the elastic vesicles on the skin permeability is supported by the ultrastructural changes observed by TEM in the intercellular lipid domains. The elastic vesicles containing 70 mol% PEG-8-L disorganize the lipid bilayers thereby creating or modifying pathways for possible drug penetration.

Animals↗
PubMedDate not supplied

Aging of the elastic and collagen fibers in the human cervical interspinous ligaments.

BACKGROUND CONTEXT: The ligaments consist of collagen bands intermingled with elastic fibers that support hundreds of pounds of stress per square inch. In the spine the basic functional unit comprises vertebrae, intervertebral disc and ligament tissues. The interspinous ligaments with the function of limiting the spine flexion are exposed to a traumatic and degenerative process that promotes pain or instability. It has been shown that aging induces structural changes to capsular, fascial and ligamentous structures, mainly to the elastic and collagen fibers. However, the relative changes with age in elastic and collagen fibers have not been quantified. PURPOSE: Examine the changes in the arrangement and amount of the elastic and collagen fibers of the human cervical interspinous ligament and attempt to correlate them with age. STUDY DESIGN/SETTING: Histomorphometric analysis of ligament samples harvested during surgery. PATIENT SAMPLE: We studied the dorsal portion of this ligament from 17 patients aged 16 to 69 years. OUTCOME MEASURES: Fraction of collagen and elastic fibers with linear regression analysis correlating fraction versus age. METHODS: The elastic and collagen fibers were identified by selective staining methods, and a blinded investigator using an image analysis system performed the histomorphometry. RESULTS: There is an age-related progressive increase in collagen and mature and elaunin elastic fibers responsible to elasticity. However, these elastic fibers showed structural degenerative changes with aging. Furthermore, there is an age-related decrease of oxytalan elastic fibers responsible to resistance. CONCLUSIONS: The aged interspinous ligament showed loss of elasticity that could alter the flexion limiting of the vertebral column.

Adolescent↗
PubMed2003

Menstrual-cycle dependence of breast parenchyma elasticity: estimation with magnetic resonance elastography of breast tissue during the menstrual cycle.

RATIONALE AND OBJECTIVES: Magnetic resonance elastography (MRE) is a promising diagnostic method that produces images with a contrast proportional to the elasticity of the tissue. This study investigated using MRE the dependence of breast tissue elasticity from the menstrual cycle of healthy volunteers. METHODS: Five volunteers (age 26-36) without breast disease and contraceptive medication were examined once weekly over 2 menstrual cycles. Examinations were performed with a 1.5 T magnet (ACS-NT, Philips Medical Systems, Best, The Netherlands). Low-frequency mechanical waves (65 Hz) were transmitted into the tissue by an oscillator. By means of a motion-sensitive spin-echo sequence, mechanical waves were displayed within the phase of the MR image and phase images were used to reconstruct the local distribution of elasticity. The elasticity of fibroglandular tissue and adipose breast tissue was analyzed individually, and the median and mean values of elasticity over the menstrual cycle were determined. RESULTS: All volunteers presented a repeating pattern concerning the elasticity over the 2 cycles. After 5 days of the onset of menses, the median value of elasticity for fibroglandular adipose tissue declined significantly by -29% (P = 0.010). After the second week of the cycle, fibroglandular tissue showed again an increase in elasticity (P = 0.028). The highest median values of elasticity were obtained during days 11 to 23 with an increase of up to 35%. For adipose tissue, only a slight and not significant variation of elasticity during the menstrual cycle was determined. CONCLUSION: MRE is able to measure a dependence of tissue elasticity on the menstrual cycle.

Adult↗
PubMed2002

Elastic proteins: biological roles and mechanical properties.

The term 'elastic protein' applies to many structural proteins with diverse functions and mechanical properties so there is room for confusion about its meaning. Elastic implies the property of elasticity, or the ability to deform reversibly without loss of energy; so elastic proteins should have high resilience. Another meaning for elastic is 'stretchy', or the ability to be deformed to large strains with little force. Thus, elastic proteins should have low stiffness. The combination of high resilience, large strains and low stiffness is characteristic of rubber-like proteins (e.g. resilin and elastin) that function in the storage of elastic-strain energy. Other elastic proteins play very different roles and have very different properties. Collagen fibres provide exceptional energy storage capacity but are not very stretchy. Mussel byssus threads and spider dragline silks are also elastic proteins because, in spite of their considerable strength and stiffness, they are remarkably stretchy. The combination of strength and extensibility, together with low resilience, gives these materials an impressive resistance to fracture (i.e. toughness), a property that allows mussels to survive crashing waves and spiders to build exquisite aerial filters. Given this range of properties and functions, it is probable that elastic proteins will provide a wealth of chemical structures and elastic mechanisms that can be exploited in novel structural materials through biotechnology.

Animals↗
PubMed2006

Viscoelastic properties of acid- and alkaline-treated human dermis: a correlation between total surface charge and elastic modulus.

BACKGROUND: One of the major mechanical functions of collagenous tissues is the storage, transmission and dissipation of elastic energy during mechanical deformation. In skin, mechanical energy is stored during loading and then is transmitted and dissipated, which protects skin from mechanical failure. Thus energy storage (elastic properties) and dissipation (viscous properties) are important characteristics of extracellular matrices. METHODS: A uniaxial incremental stress relaxation test method has been used to characterize the time-dependent (viscous) and time-independent (elastic) properties of human dermis. Viscoelasticity was investigated in processed human dermis that was equilibrated at pHs of 3.0, 7.4 and 11.0 in an effort to study the link between electrostatic interactions within the collagen matrix and macroscopic tissue properties. RESULTS: Our results show that the solution pH and the charge on collagen significantly affected the high-strain elastic behavior of dermis; the elastic behavior of skin has previously been shown to be directly correlated with axial stretching of the collagen triple helix in crosslinked collagen fibrils. A positive linear correlation existed between the high-strain elastic modulus and both pH (R(2)=0.96) and the total number of charged residues on collagen (R(2)=0.93). These results provide in vitro/ex vivo evidence that charged groups on the surface of collagen molecules in processed human skin influence the high-strain elastic properties of dermis and are likely to be involved in elastic energy storage. CONCLUSION: It is proposed that the pH and charged residue dependency of the elastic modulus suggests that charged pair interactions and repulsions within and between collagen molecules are involved in elastic energy storage during stretching at high strains. It is hypothesized that elastic energy storage is associated with the stretching of pairs of charged amino acid residues that are found primarily in the flexible regions of collagen molecules.

Collagen↗
PubMed2004

The concentration of elastic fibres in the male urethra during human fetal development.

OBJECTIVE: To describe the distribution of elastic fibres in the developing male urethra and to provide stereological data of the concentration of elastic fibres in the human urethra. MATERIALS AND METHODS: Urethras were obtained from 10 fresh normal human fetuses at 15-36 weeks of gestation. A place-matched spongy urethra of a 27-year-old normal adult man was also analysed. Samples were fixed in Bouin's solution, embedded in paraffin and histologically processed. The elastic system fibres were evaluated by light microscopy using Weigert's resorcin-fuchsin technique after oxidation. Morphometric values were assessed by the point-counting method. The volumetric density (Vv) of elastic fibres was correlated with fetal age. RESULTS: At 15 weeks the elastic fibres were sparse and homogeneously distributed. The size and thickness of elastic fibres increased with age, mainly in the third trimester of gestation. Elastic fibres formed a randomly orientated network in the trabeculae of the corpus spongiosum. The mean (sem) Vv of elastic fibres in the spongy urethra was 5.2 (0.4)% in the fetus at 15 weeks and 14.8 (1.0)% at 36 weeks. In the urethra of the place- matched young man the Vv was 19.0 (1.3)%. The concentration of elastic fibres in the spongy urethra increased significantly with age. CONCLUSION: The high concentration of elastic fibres in the spongy urethra may partly explain its high extensibility. The progressive increase in elastic fibres during development implies functional adaptation of the fetal male urethra.

Elastic Tissue↗
PubMed2001

Effect of light power density on development of elastic modulus of a model light-activated composite during polymerization.

PURPOSE: Elastic modulus development during polymerization of a composite is a measure of the polymerization maturity and the restoration's ability to transfer stress to enamel and dentin. The characteristics of elastic modulus development in real time during cure are largely unknown. The purpose of this study was to evaluate the effect of light power density and total energy density on the early development of elastic modulus for a light-activated composite. METHODS: Cylindrical specimens of a model hybrid composite were tested in flexure in a dynamic mechanical analyzer (DMA). Specimens were light-activated (Variable Intensity Polymerizer, Bisco, Itasca, Illinois) for 60 seconds. Elastic modulus was measured continuously for 5 minutes from the start of light activation. Development of elastic modulus was assessed for six different light power densities and two reduced power density levels given at longer exposure duration to provide similar energy density values. One-way analysis of variance with Tukey's post hoc comparison test was used to evaluate significant differences of elastic modulus at p = .05. RESULTS: The rates of elastic modulus development and final moduli were dependent on the light power density applied. Composite specimens cured by equivalent energy densities using short times and high power density or long times and low power density produced equivalent elastic moduli. Elastic moduli for emitted power densities between 400 and 600 mW/cm2 (160-260 mW/cm2 measured at the specimen surface) were not significantly different (p > .05). CONCLUSIONS: Light power densities greater than 160 mW/cm2 measured at the specimen surface resulted in elastic moduli that were not significantly different. Equivalent energy densities produced comparable elastic moduli.

Analysis of Variance↗
PubMed1984

The three-dimensional configuration of the elastic fiber network in canine saphenous vein. A stereo scanning electron microscopic study.

Stereo scanning electron microscopy was used to study the normal arrangement of elastic fibers in canine saphenous veins. Selective alkali digestion and autoclaving exposed a network of interconnecting elastic fibers throughout the venous wall. 14 normal saphenous veins were surgically removed from 7 healthy dogs. Unfixed 1-cm segments of the isolated specimens were digested by sonication for 30 min in 0.5 N NaOH solution and then autoclaved for 30 min. The digested specimens were then fixed and routinely prepared for scanning electron microscopy. Large longitudinally oriented fibers in each tunica branched and anastomosed with adjacent fibers. Small fibers branched off at almost right angles and interconnected the longitudinal fibers. The configuration of the elastic network varied between the tunicae of the venous wall. The different networks were interconnected by anastomosing fibers of adjacent tunica to form a single elastic cylinder throughout the venous wall. The internal elastic lamina consisted of a single layer of fibers with a fishnet-like arrangement around the periphery of the luminal surface. Large, longitudinally oriented elastic fibers of the tunica media branched and anastomosed as in the internal elastic lamina. However, they also had tangential orientation and traversed different levels within the media. As a result, stratified layers were not formed. The external lamina consisted of several parallel layers of longitudinally oriented ribbons of elastic. Thick fibers interconnected these broad ribbons on the same and adjacent levels to form discontinuous layers. The configuration of the elastic network of the canine saphenous vein is compared to that previously reported for human saphenous vein. It is suggested that the architecture of this elastic network would contribute to vascular integrity and flexibility as well as aid in the distribution of stress throughout the venous wall. Basic knowledge of the elastic fiber network in this vein may be applied to future studies of diseased and grafted vessels.

Animals↗
PubMed2006

Quantification of the roles of trabecular microarchitecture and trabecular type in determining the elastic modulus of human trabecular bone.

UNLABELLED: The roles of microarchitecture and types of trabeculae in determining elastic modulus of trabecular bone have been studied in microCT images of 29 trabecular bone samples by comparing their Young's moduli calculated by finite element analysis (FEA) with different trabecular type-specific reconstructions. The results suggest that trabecular plates play an essential role in determining elastic properties of trabecular bone. INTRODUCTION: Osteoporosis is an age-related disease characterized by low bone mass and architectural deterioration. Other than bone volume fraction (BV/TV), microarchitecture of bone is also believed to be important in governing mechanical properties of trabecular bone. We quantitatively examined the role of microarchitecture and relative contribution of trabecular types of individual trabecula in determining the elastic property of trabecular bone. MATERIALS AND METHODS: Twenty-nine human cadaveric trabecular bone samples were scanned at 21-mum resolution using a microCT system. Digital topological analysis (DTA) consisting of skeletonization and classification was combined with a trabecular type-specific reconstruction technique to extract the skeleton and identify topological type of trabeculae of the original trabecular bone image. Four different microCT-based finite element (FE) models were constructed for each specimen: (1) original full voxel; (2) skeletal voxel; (3) rod-reconstructed, preserving rod volume and plate skeleton; and (4) plate-reconstructed, preserving plate volume and rod skeleton. For each model, the elastic moduli were calculated under compression along each of three image-coordinate axis directions. Plate and rod tissue fractions directly measured from DTA-based topological classification were correlated with the elastic moduli computed from full voxel model. RESULTS: The elastic moduli of skeleton models were significantly correlated with those of full voxel models along all three coordinate axes (r(2) = 0.38 approximately 0.53). The rod-reconstructed model contained 21.3% of original bone mass and restored 1.5% of elastic moduli, whereas the plate-reconstructed model contained 90.3% of bone mass and restored 53.2% of elastic moduli. Plate tissue fraction showed a significantly positive correlation (r(2) = 0.49) with elastic modulus by a power law, whereas rod tissue fraction showed a significantly negative correlation (r(2) = 0.42). CONCLUSIONS: These results quantitatively show that the microarchitecture alone affects elastic moduli of trabecular bone and trabecular plates make a far greater contribution than rods to the bone's elastic behavior.

Aged↗
PubMed1975

[Elastic modulus of dental porcelains by dynamic method (author's transl)].

Using an equipment with sensitive vibretor-controller oscillater of elactrostatic drive system, we sought for the difference between elastic modulus of various kinds of dental porcelain and elastic modulus by firing method. We examined the relation between temperature of firing and elastic modulus as well. The obtained results are as follows: 1). Elastic modulus of low fusing porcelain of enamel color was 4.32 times 10(11) dyn/cm2 by air firing 3.95 approximately 4.63 times 10(11) dyn/cm2 by vacuum firing. Low fusing of porcelain of dentin color and the one of enamel color had the same elastic modulus. 2). Elastic modulas of high fusing porcelain of enamel color was 3.58 times 10(11) dyn/cm2 by air firing, 3.41 approximately 3.64 times 10(11) dyn/cm2 by vacuum firing. High fusing porcelain of dentin color and the one of enamel color were of the same elastic modulus. 3). Porcelain of opaque color for metal bond was 3.22 times 10(11) dyn/cm2 by air firing 3.97 approximately 4.22 times 10(11) dyn/cm2 by vacuum firing. When dentin color was added to opaque color elastic modulus was low (3.90 times 10(11) dyn/cm2). 4). Alumina porcelain of opaque color was 5.42 times 10(11) dyn/cm2 by air firing, 6.50 approximately 6.80 times 10(11) dyn/cm2 by vacuum firing. When dentin color was added to opaque color elastic modulus was very low (3.90 times 10(11) dyn/cm2). 5). Elastic modulus to various kinds porcelain changes according to temprature of fusing. And the highest elastic modulus is at the temperature which is 50 approximately 100 degrees C lower than final firing temperature.

Dental Porcelain↗
PubMed2003

A comparison of dynamic and static testing of latex and nonlatex orthodontic elastics.

The purpose of this study was to determine the effects of repeated stretching (cyclic testing) and static testing on the force decay properties of two different types of orthodontic elastics from a single supplier. Samples of American Orthodontics' 0.25 inch, 4.5 oz (6.35 mm, 127.5 g) latex and nonlatex elastics were used and a sample size of 12 elastics per group was tested. Static testing involved stretching the elastics to three times marketed internal diameter (19.05 mm) and measuring force levels at intervals over 24 hours. Cyclic testing used the same initial extension but cycled the elastics an additional 24.7 mm to simulate extension with maximal opening in the mouth. Both types of elastic had similar initial forces that were statistically below the marketed force (122 and 118 g for latex and nonlatex elastics, respectively) at three times marketed internal diameter. Cyclic testing caused significantly more force loss and this difference occurred primarily within the first 30 minutes. For statically tested elastics the percentage of initial force remaining at 4, 8, and 24 hours was 87%, 85%, 83%, and 83%, 78%, 69% for latex and nonlatex elastics, respectively. For cyclically tested elastics the percentage of initial force remaining at 4, 8, and 24 hours was 77%, 76%, 75%, and 65%, 63%, 53% for latex and nonlatex elastics, respectively.

Analysis of Variance↗
PubMed1988

Pulmonary elastic fiber degradation in paraquat toxicity. An electron microscopic immunohistochemical study.

To study the morphologic alterations of pulmonary elastic fibers in cynomolgus monkeys with paraquat toxicity, peroxidase- and ferritin-labeled antielastin antibodies were used for the light and electron microscopic localization of elastin. One week after paraquat, alveolitis, tissue damage and alveolar dilatation were present; elastic fibers were frayed and more diffusely and intensely stained than those of control animals. In the latter, staining was localized in peripheral regions of the amorphous components and, to a lesser extent, in some microfibrils of elastic fibers. At 3 to 4 weeks, diffuse staining was evident in damaged interstitial elastic fibers and in newly formed elastic fibers in areas of intraalveolar fibrosis. At 8 weeks, the interstitium contained many elastic fibers which showed staining only in peripheral regions of the amorphous components. These observations suggest that: 1) preembedding immunohistochemical staining for elastin is localized in peripheral regions of normal elastic fibers because the antielastin antibody can penetrate into mature and undamaged amorphous components only to a very limited extent; 2) in early stages of paraquat toxicity this staining is more diffuse and intense because elastase from inflammatory cells partially degrades the elastic fibers and permits greater penetration of the antibody into the amorphous materials; 3) in later stages the staining pattern returns to normal as inflammation subsides and elastic fibers are repaired; however, newly formed elastic fibers in areas of intraalveolar fibrosis stain diffusely, reflecting increased penetration of the antibody because of immaturity and incomplete cross-linking, and 4) degeneration of elastic fibers of alveolar walls in paraquat lung may lead to alveolar dilatation, which is associated with irregular fibrosis and constitutes one of the processes of pulmonary structural remodeling in paraquat lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗