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The Effect of Prestretching on Force Degradation of Synthetic Elastomeric Chains
Fattahi HR.,Poursayah A.
Journal of Dentistry , 2011,
Abstract: Statement of Problems: The main disadvantage of elastic chains is their rapid force decay. Thus, pre-stretching has been recommended as a method to overcome this ever existing problem. However, the information regarding the magnitude and the method of its performance are still obscure or varied. Purpose: This study was designed to evaluate the effect of pre-stretching on force degradation of the synthetic elastomeric chains. Materials and Method: This experimental study had two categories of synthetic elastomeric chains: 1. Control (unprestretched) 2. Test (prestretched). The test groups were pre-stretched to 33%, 100% and 200% of the original length. We evaluated 4 control and 16 test groups from four manufacturers. In a period of 5 seconds, each specimen was pre-stretched in the rate of 30 mm per minute. Then, all the specimens were stretched to 25 mm and fixed in this distance on the frames and were merged in 37 degree water. Their forces were measured at 0 hour, 1 hour, 24 hours, 1 week, and 3 weeks. Data were analyzed using Friedman, ANOVA and Green house-Geisser test.Results: All the 20 groups had force degradation in the study period ( p <001). The highest rate of force degradation (about half of the total force degradation) occurred at the first hour. But the rate of force degradation declined over time. In all brands, force degradation was smaller in pre-stretching 200% than the control group ( p <0.01-0.001). Conclusion: Synthetic elastomeric chains from several companies have different effects from different distances of pre-strectching, so the appropriate pre-stretching length must be defined for each kind of synthetic elastomeric chain.
An in vitro comparison of the force decay generated by different commercially available elastomeric chains and NiTi closed coil springs
Santos, Ana Cristina Soares;Tortamano, André;Naccarato, Sandra Regina Frazatto;Dominguez-Rodriguez, Gladys Cristina;Vigorito, Julio Wilson;
Brazilian Oral Research , 2007, DOI: 10.1590/S1806-83242007000100009
Abstract: this in vitro study was designed to compare the forces generated by commercially available elastomeric chains and niti closed coil springs, and to determine their force decay pattern. forty elastomeric chains and forty niti closed coil springs were divided into 4 groups according to the following manufacturers: (1) morelli?, (2) abzil?, (3) tp orthodontics? and (4) american orthodontics?. the specimens were extended to twice their original length and stored in artificial saliva at 37°c. initial force was measured by means of an instron universal testing machine and then at 1, 4, 7, 14, 21, and 28 days. the results revealed that the elastomeric chains delivered a mean initial force of 347 g for morelli?, 351 g for american orthodontics?, 402 g for abzil?, and 404 g for tp orthodontics?. the niti closed coil springs generated a mean initial force of 196 g for american orthodontics?, 208 g for tp orthodontics?, 216 g for abzil?, and 223 g for morelli?. the mean percentage of force decay observed after 28 days for the elastomeric chains was 37.4% for tp orthodontics?, 48.1% for american orthodontics?, 65.4% for morelli?, and 71.6% for abzil?. after 28 days, the niti closed coil springs presented a mean percentage of force decay of 22.6% for american orthodontics?, 29.8% for abzil?, 30.6% for morelli?, and 45.8% for tp orthodontics?. at the end of the study, significant differences were observed between the elastomeric chains and the niti closed coil springs. the results indicated that the studied niti closed coil springs are more adequate for dental movement than the elastomeric chains.
In vitro evaluation of force degradation of elastomeric chains used in Orthodontics  [cached]
André Weissheimer,Arno Locks,Luciane Macedo de Menezes,Adriano Ferreti Borgatto
Dental Press Journal of Orthodontics , 2013,
Abstract: OBJECTIVE: To analyze the in vitro force degradation of four different brands of elastomeric chains: American Orthodontics, Morelli, Ormco and TP Orthodontics. METHODS: The sample consisted of 80 gray elastomeric chains that were divided into four groups according to their respective manufacturers. Chain stretching was standardized at 21 mm with initial force release ranging from 300 g to 370 g. The samples were kept in artificial saliva at a constant temperature of 37°C and the degradation force was recorded at the following time intervals: initial, 1, 3, 5, 7 and 9 hours, and 1, 7, 14, 21, 28, and 35 days. RESULTS: There was a statistically significant difference between the groups regarding the force degradation, mainly within the first day, as a force loss of 50-55% was observed during that time in relation to the initial force. The force delivered at 35 days ranged from 122 g to 148 g. CONCLUSION: All groups showed force degradation over time, regardless of their trademarks, a force loss of 59-69% was observed in the first hour compared to baseline. However, because the variation in force degradation depends on the trademark, studies such as the present one are important for guiding the clinical use of these materials. OBJETIVO: analisar, in vitro, a degrada o de for a, ao longo do tempo, de elast meros das marcas comerciais American Orthodontics, Morelli, Ormco e TP Orthodontics. MéTODOS: a amostra constituiu-se de 80 segmentos de elast meros em cadeia fechada na cor cinza, divididos em quatro grupos, conforme o fabricante. A distens o foi padronizada em 21mm, com libera o de for a inicial variando de 300 a 370g de for a. As amostras foram mantidas em saliva artificial em temperatura constante de 37oC, e a for a avaliada nos seguintes intervalos: inicial, 1h, 3h, 5h, 7h, 9h, 1 dia, 7 dias, 14 dias, 21 dias, 28 dias e 35 dias. RESULTADOS: houve diferen a estatisticamente significativa na degrada o de for a entre os grupos avaliados, sendo que no primeiro dia houve perda de 50 a 55% em rela o à for a inicial. Os valores médios de for a em 35 dias variaram de 122 a 148g. CONCLUS O: todas as marcas comerciais apresentaram degrada o de for a ao longo do tempo, sendo que na primeira hora a perda de for a esteve entre 59 e 69% da for a inicial. Porém, como existe varia o dessa degrada o dependendo da marca comercial, estudos como esses s o importantes para orienta o do uso desses elast meros.
A Comparative Study on the Efficiency of Pigmented and non Pigmented Elastomeric Chains Using Differential Scanning Calorimetry  [PDF]
Joby Paulose,Rhea Mini Jayan
Indian Journal of Dental Advancements , 2010,
Abstract: Orthodontic treatment involves the use of force delivery systems such as arch wires and elastomeric chains. Their mechanical property varies among various manufacturers. It depends on their phase transformation temperature. Differential scanning calorimetry (DSC) is a method of thermal analysis which is extensively employed to assess the properties of orthodontic materials. In the field of orthodontics DSC is used to assess the phase transition temperature of orthodontic arch wires, glass transition temperature of polyurethane elastomers, and to evaluate the degree of cure of dental resins. The present study highlights the clinical application of differential scanning calorimetry in evaluating the Glass transition temperature of polyurethane elastomeric chains.
Force Chains, Microelasticity and Macroelasticity  [PDF]
C. Goldenberg,I. Goldhirsch
Physics , 2001, DOI: 10.1103/PhysRevLett.89.084302
Abstract: It has been claimed that quasistatic granular materials, as well as nanoscale materials, exhibit departures from elasticity even at small loadings. It is demonstrated, using 2D and 3D models with interparticle harmonic interactions, that such departures are expected at small scales [below O(100) particle diameters], at which continuum elasticity is invalid, and vanish at large scales. The models exhibit force chains on small scales, and force and stress distributions which agree with experimental findings. Effects of anisotropy, disorder and boundary conditions are discussed as well.
Heterogeneous Force Chains in Cellularized Biopolymer Network  [PDF]
Long Liang,Christopher Jones,Bo Sun,Yang Jiao
Physics , 2015,
Abstract: Biopolymer Networks play an important role in coordinating and regulating collective cellular dynamics via a number of signaling pathways. Here, we investigate the mechanical response of a model biopolymer network due to the active contraction of embedded cells. Specifically, a graph (bond-node) model derived from confocal microscopy data is used to represent the network microstructure, and cell contraction is modeled by applying correlated displacements at specific nodes, representing the focal adhesion sites. A force-based stochastic relaxation method is employed to obtain force-balanced network under cell contraction. We find that the majority of the forces are carried by a small number of heterogeneous force chains emitted from the contracting cells. The force chains consist of fiber segments that either possess a high degree of alignment before cell contraction or are aligned due to the reorientation induced by cell contraction. Large fluctuations of the forces along different force chains are observed. Importantly, the decay of the forces along the force chains is significantly slower than the decay of radially averaged forces in the system. These results suggest that the fibrous nature of biopolymer network structure can support long-range force transmission and thus, long-range mechanical signaling between cells.
Determination of Sugars in Sports Drinks
Itsusei Fujita,Toshiaki Tobino
Journal of Food Technology , 2013, DOI: 10.3923/jftech.2011.139.140
Abstract: Mono and disaccharides are routinely quantified with a differential refractometer. However, the researchers developed a simpler analytical method involving pre-derivatization and high-performance liquid chromatography to achieve a high recovery rate. The purpose of the study is to understand the amount of sugar in sports drinks in order to determine how large doses lead to tooth decay. To dose so the researchers quantified sugars in sports drinks.
Structural transition of force chains observed by mechanical spectroscopy  [PDF]
Wan-Jing Wang,Kai-Wei Yang,Xue-Bang Wu,Yu-Bing Wang,Zhen-Gang Zhu
Physics , 2008,
Abstract: The dissipation properties of a fine sand system are investigated by a low-frequency mechanical spectroscopy. The experiments show many interesting profiles of the relative energy dissipation, which imply that some structural transition of force chains in dense granular media has occurred. The following data and discussion indicate that the transition of force chains will lead to the small deformation of arrangement in the granular system, which is responsible for the historical effects. We hope this research can improve our knowledge of the microstructure of the granular materials.
Stresses in isostatic granular systems and emergence of force chains  [PDF]
Raphael Blumenfeld
Physics , 2004, DOI: 10.1103/PhysRevLett.93.108301
Abstract: Progress is reported on several questions that bedevil understanding of granular systems: (i) are the stress equations elliptic, parabolic or hyperbolic? (ii) how can the often-observed force chains be predicted from a first-principles continuous theory? (iii) How to relate insight from isostatic systems to general packings? Explicit equations are derived for the stress components in two dimensions including the dependence on the local structure. The equations are shown to be hyperbolic and their general solutions, as well as the Green function, are found. It is shown that the solutions give rise to force chains and the explicit dependence of the force chains trajectories and magnitudes on the local geometry is predicted. Direct experimental tests of the predictions are proposed. Finally, a framework is proposed to relate the analysis to non-isostatic and more realistic granular assemblies.
Sound propagation and force chains in granular materials  [PDF]
Eli T. Owens,Karen E. Daniels
Physics , 2010, DOI: 10.1209/0295-5075/94/54005
Abstract: Granular materials are inherently heterogeneous, leading to challenges in formulating accurate models of sound propagation. In order to quantify acoustic responses in space and time, we perform experiments in a photoelastic granular material in which the internal stress pattern (in the form of force chains) is visible. We utilize two complementary methods, high-speed imaging and piezoelectric transduction, to provide particle-scale measurements of both the amplitude and speed of an acoustic wave in the near-field regime. We observe that the wave amplitude is on average largest within particles experiencing the largest forces, particularly in those chains radiating away from the source, with the force-dependence of this amplitude in qualitative agreement with a simple Hertzian-like model of particle contact area. In addition, we are able to directly observe rare transient force chains formed by the opening and closing of contacts during propagation. The speed of the leading edge of the pulse is in quantitative agreement with predictions for one-dimensional chains, while the slower speed of the peak response suggests that it contains waves which have travelled over multiple paths even within just this near-field region. These effects highlight the importance of particle-scale behaviors in determining the acoustical properties of granular materials.
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