Maximum Load Values Research Articles

Simultaneous multiple element detection by particle beam/hollow cathode-optical emission spectroscopy as a tool for metallomic studies: Determinations of metal binding with apo-transferrin

Particle beam/hollow cathode-optical emission spectroscopy (PB/HC-OES) is presented as a tool for the determination of metal ion loading in transferrin (Tf). The elemental specificity of optical emission spectroscopy provides a means of assessing metal ion concentrations as well as the relative amounts of metal per unit protein concentration (up to 2 moles of Fe per mole of protein). The PB/HC-OES method allows for the simultaneous detection of metal content (Fe (I) 371.99, Ni (I) 341.41 nm, Zn (I) 213.86 nm, and Ag (I) 338.28 nm in this case), as well as elemental carbon and sulfur (C (I) 156.14 nm and S (I) 180.73 nm) that are reflective of the protein composition and concentration. Quantification for the metal species is based on calibration functions derived from aqueous solutions, with limits of detection for the entire suite being less than 1.0 μM. Determinations in this manner eliminate much of the ambiguity inherent in UV-VIS absorbance determinations of Tf metal binding. Validation of this method is obtained by analyzing loading response of Fe(3+) into Tf using the PB/HC-OES method and comparing the results with those of the standard UV-VIS absorbance method. Maximum Fe(3+) loading of Tf (based on the number of available binding sites) was determined to be 71.2 ± 4.7% by the PB/HC-OES method and 67.5 ± 2.5% for the UV-VIS absorbance method. Element emission ratios between the dopant metals and the carbon and sulfur protein constituents allow for concentration independent determinations of metal binding into Tf. Loading percentages were determined for Ni(2+), Zn(2+), and Ag(+) into Tf with maximum loading values of 19.5 ± 0.4%, 41.0 ± 4.4%, and 141.2 ± 4.3%, respectively. While of no apparent biological significance, Ag(+) presents an interesting case as a surrogate for Pt(2+), whose binding with Tf has shown to be quite different from the other metals. A different mode from the others is indeed observed, and is consistent with conjecture on the Pt(2+) mechanisms. Competitive binding studies not easily performed using absorbance spectroscopy are easily performed by simultaneous, multielement analysis, reflective of the metals and the protein content. In this work, there is clear competition between and Fe(3+) and Zn(2+) for binding in the C-terminus lobe of Tf, while Ni(2+) binds within the N-terminus lobe. Addition of Ag(+) to this mixture does not affect the other metals' distributions, but reflects binding at other protein sites.

Fracture Resistance and Deflection of Pulpless Anterior Teeth Restored with Composite or Porcelain Veneers

Introduction The aim of this in vitro study was to evaluate the influence that resin composite and porcelain veneer restorations, associated or not to fiber post placement, have on fracture resistance and deflection of pulpless anterior teeth. Methods One hundred twenty freshly extracted human maxillary central incisors were selected. Teeth were randomly divided into 7 experimental groups (veneer preparation/resin composite veneer placement/endodontic therapy and resin composite veneer placement/endodontic therapy, fiber post and resin composite veneer placement/porcelain veneer placement/endodontic therapy and porcelain veneer placement/endodontic therapy, fiber post and porcelain veneer placement) and a control group (n = 15). Specimens were loaded to fracture recording crown deflection, and data were statistically analyzed. Results Veneer preparations did not significantly influence fracture resistance of incisors. On the contrary, veneer preparation significantly increased specimen deflection values. Fiber posts seemed to significantly increase mean maximum load values for endodontically treated teeth restored with either composite or porcelain veneers. Conclusions A fiber post restoration can be suggested when endodontic treatment is associated with veneer restoration. Veneer restorations seem to be an optimal choice also for endodontically treated teeth.

Effect of Surface Preparation on the Failure Load of a Highly Filled Composite Resin Bonded to a Denture Base Resin

The purpose of this study was to evaluate the effect of the surface preparation on the maximum fracture load value of a highly filled gingival shade composite resin bonded to a denture base resin. Block specimens were prepared from a heat-processed denture base resin and divided into five groups. The flat surfaces of the specimens were abraded with 400-grit silicon carbide paper, then prepared in one of the following ways: (1) without preparation (group 1); (2) application of silane coupling agent (group 2); (3) application of dichloromethane (group 3); (4) application of dichloromethane following the silane coupling agent (group 4); or (5) tribochemical silica coating (group 5). A highly filled gingival shade composite resin was applied (area diameter= 5 mm) and polymerized with a light polymerizing unit. Specimens made entirely of heat-processed denture base resin were also fabricated as references (group 6). The halves of the specimens of groups 4, 5, and 6 were thermocycled up to 10,000 times in water between 5 degrees C and 55 degrees C with a 1-minute dwell time at each temperature. Shear testing was performed in a universal testing machine at a crosshead speed of 1 mm/min, and the maximum fracture load values were determined (n = 10). The maximum fracture load values of the highly filled gingival shade composite resin bonded to the denture base resin for all preparation groups were significantly enhanced before thermocycling (p < 0.05). Group 5 exhibited the greatest fracture load value, followed by group 4, compared to the other groups (p < 0.05), however, the fracture load values significantly decreased for these groups after thermocycling (p < 0.05), whereas the fracture load value of group 6 did not decrease (p > 0.05). Tribochemical silica coating and the application of dichloromethane after the silane coupling agent were effective surface preparations for the bonding of a highly filled gingival shade composite resin to a denture base resin, however, the bond durability of these treatments may be insufficient.

Comparative effects of risedronate, atorvastatin, estrogen and SERMs on bone mass and strength in ovariectomized rats

Objective The aim of this study was to investigate bone protective effects of risedronate, atorvastatin, raloxifene and clomiphene citrate in ovariectomized rats. Methods Our study was conducted on 63 rats at Experimental Research Center of Celal Bayar University. Six-month-old rats were divided into seven groups. There were five drug administered ovariectomized groups, one ovariectomized control group without drug administration and one non-ovariectomized control group without drug administration. Eight weeks postovariectomy, rats were treated with the bisphosphonate risedronate sodium, the statin atorvastatin, the estrogen 17β-estradiol and the selective estrogen receptor modulators (SERMs) raloxifene hydrochloride and clomiphene citrate by gavage daily for 8 weeks. At the end of the study, rats were killed under anesthesia. For densitometric evaluation, left femurs and tibiae were removed. Left femurs were also used to measure bone volume. Right femurs were used for three-point bending test. Results Compared to ovariectomized group, femur cortex volume increased significantly in non-ovariectomized group ( p = 0.016). Compared to non-ovariectomized group, distal femoral metaphyseal and femur midshaft bone mineral density values were significantly lower in ovariectomized group ( p = 0.047). In ovariectomy + atorvastatin group, whole femur and femur midshaft bone mineral density and three-point bending test maximal load values were significantly higher than ovariectomized group ( p = 0.049, 0.05, and 0.018). When compared to the ovariectomized group, no significant difference was found with respect to femoral maximum load values in groups treated with risedronate, estrogen, raloxifene and clomiphene ( p = 0.602, 0.602, 0.75, and 0.927). In ovariectomy + risedronate group, femur midshaft bone mineral density values were significantly higher than the values in ovariectomized group ( p = 0.023). When compared to ovariectomized group, no significant difference was found with respect to femur midshaft bone mineral density values in groups treated with estrogen, raloxifene and clomiphene ( p = 0.306, 0.808, and 0.095). Conclusions While risedronate sodium prevented the decrease in bone mineral density in ovariectomized rats, atorvastatin maintained mechanical characteristics of bone and also prevented the decrease in bone mineral density as risedronate sodium.

Effect of Surface Preparation on the Failure Load of a Highly Filled Composite Bonded to the Polymer‐Monomer Matrix of a Fiber‐Reinforced Composite

The purpose of the present study was to evaluate the effect of surface preparation on the maximum fracture load value of a highly filled composite bonded to the polymer-monomer matrix of a fiber-reinforced composite. A polymer-monomer matrix was made by mixing urethane dimethacrylate and triethyleneglycol dimethacrylate at a ratio of 1:1 with camphorquinone and 2-dimethylaminoethyl methacrylate as a light initiator. The matrix was then polymerized in a disk-shaped silicone mold with a light-polymerizing unit. The flat surfaces of the polymer-monomer matrix disk were prepared in one of the following ways: (1) without preparation; (2) application of silane coupling agent; or (3) application of matrix liquid and prepolymerization. A highly filled composite material was applied and polymerized with a light-polymerizing unit. Additional test specimens made entirely of the polymer-monomer matrix were fabricated as references; the disk and cylinder were fabricated in one piece using a mold specially made for the present study (group 4). Half the specimens were thermocycled up to 10,000 times in water with a 1-minute dwell time at each temperature (5 degrees C and 55 degrees C). The maximum fracture load values were determined using a universal testing machine (n = 10). The maximum fracture loads for group 3 were significantly enhanced both before and after thermocycling, whereas the maximum fracture loads of group 2 were significantly enhanced before thermocycling (p < 0.05); however, the failure loads decreased for all groups after thermocycling (p < 0.05). All the specimens in groups 1 and 2 debonded during thermocycling. The failure load of group 3 was significantly lower than that of group 4 both before and after thermocycling (p < 0.05). Within the limitations of the current in vitro study, the application and prepolymerization of a mixed dimethacrylate resin liquid prior to the application of a highly filled composite was an effective surface preparation for the polymer-monomer matrix of a fiber-reinforced composite; however, the bond durability may be insufficient.

Buckling of the SSFF rectangular orthotropic plate under in-plane pure bending

The paper deals with the solution of the buckling problem for a rectangular orthotropic plate with two parallel free edges. The other two parallel simply supported opposite edges of the plate are loaded by a linearly distributed in-plane load which is equivalent to the pure in-plane bending. Buckling analysis is performed using the Levy-type solution and subsequent finite-difference approximation of the boundary-value problem. Solution of the corresponding eigenvalue problem yields the critical buckling coefficient and critical load. The problem is solved for isotropic and orthotropic composite plates. The design chart has been obtained for the isotropic plates with various aspect ratios from which the corresponding critical loads can be found. Critical buckling coefficients are determined for composite plates with various aspect ratios and angles of the reinforcement orientation. The optimum material reinforcement structure providing the maximum value of critical load is determined.

Arsenic levels in wipe samples collected from play structures constructed with CCA-treated wood: Impact on exposure estimates

Lumber treated with chromated copper arsenate (CCA) has been used in residential outdoor wood structures and playgrounds. The U.S. EPA has conducted a probabilistic assessment of children's exposure to arsenic from CCA-treated structures using the Stochastic Human Exposure and Dose Simulation model for the wood preservative scenario (SHEDS-Wood). The EPA assessment relied on data from an experimental study using adult volunteers and designed to measure arsenic in maximum hand and wipe loadings. Analyses using arsenic handloading data from a study of children playing on CCA-treated play structures in Edmonton, Canada, indicate that the maximum handloading values significantly overestimate the exposure that occurs during actual play. The objective of our paper is to assess whether the dislodgeable arsenic residues from structures in the Edmonton study are comparable to those observed in other studies and whether they support the conclusion that the values derived by EPA using modeled maximum loading values overestimate hand exposures. We compared dislodgeable arsenic residue data from structures in the playgrounds in the Edmonton study to levels observed in studies used in EPA's assessment. Our analysis showed that the dislodgeable arsenic levels in the Edmonton playground structures are similar to those in the studies used by EPA. Hence, the exposure estimates derived using the handloading data from children playing on CCA-treated structures are more representative of children's actual exposures than the overestimates derived by EPA using modeled maximum values. Handloading data from children playing on CCA-treated structures should be used to reduce the uncertainty of modeled estimates derived using the SHEDS-Wood model.

Low dose X-irradiation promotes callus mineralization: experiment with rats

To investigate the effect of low dose irradiation (LDI) on callus formation and mineralization. 80 SD rats were subjected to standard closed fracture on right femur so as to establish animal models and then were randomly divided into 2 equal groups: LDI group undergoing low dose whole body X-ray irradiation of 1Gy right after fracture induction and control group without irradiation. 1, 2, 3, 4, and 8 weeks later blood samples were collected from the heart to examine the amounts of white blood cells and platelets and alkaline phosphatase (ALP) level. Conventional X-ray films were taken and MicroCT was conducted to evaluate the callus bridging. Then the rats were killed to take out the femurs to undergo histological examination. Peripheral quantitative computed tomography (pQCT) was conducted to quantify the bone mineral content (BMC). Four-point bending test was used to examine the mechanical properties of the callus. The maximum load value and histological score 2 weeks later of the LDI group were both lower than those of the control group, however, the serum ALP, BMC, maximum load level, callus bridging score, and histological score 3 weeks later of the LDI group were all significantly higher than those of the control groups (all P<0.05). 4 and 8 weeks later there were not significant differences in all these parameters between the 2 groups. The WBC amount in the first 2 weeks of experiment of the LDI group was remarkably lower in these 2 groups, however, in the third week, the WBC value of the LDI group was higher than that of the control group (P<0.05). LDI promotes the mineralization at the stage of hard callus formation which is probably associated with progenitor cell mobilization.

Study of Li 2TiO 3 + 5 mol% TiO 2 lithium ceramics after long-term neutron irradiation

Given work presents the results of complex material-science studies of 1 mm diameter ceramic pebbles manufactured of Li 2TiO 3 + 5 mol% TiO 2 ceramics before and after long-time neutron irradiation. Ceramic samples were placed in specially ampoules (six items) made of stainless steel Cr18Ni10Ti which were vacuumized and filled with helium. Irradiation of ampoules was carried out in the loop channel of WWRK reactor (Almaty, Kazakhstan) during 223 days at 6 MW power. After irradiation light-colored pebbles became grey-colored due to structure changes which generation of grey-colored inclusions (lithium oxide) with low density and microhardness. There is a radiation softening of lithium ceramic and that effect is higher for lower irradiation temperature 760 K than for 920 K. The value of maximum permissible load (pebble crash limit) at that is low and comprises ∼37.9 N. The content of residual tritium is higher for ceramic irradiated at 760 K (6.6 ± 0.6 × 10 11 Bq/kg) than for ceramic irradiated at 920 K (17 ± 3 × 10 10 Bq/kg). The size change indicates that pebble increase more after irradiation at 760 K than at 920 K where the bigger portion of tritium leaves the pebble. X-ray analysis shows radiation modification of Li 2TiO 3 + 5 mol% TiO 2 phase composition and generation of new phases: LiTi 2O 4, LiTiO 2 and Li 4Ti 5O 12.

Equilibrated divergence measure stress tensor fields for heavy masonry bodies

Abstract In this paper we study the equilibrium problem of rectangular panels made of no-tension material under gravity and undergoing a vertical load distributed on their top and a horizontal load distributed on a lateral side. Equilibrated and negative semi-definite stress fields are presented which are tensor-valued measure whose distributional divergence is a vector-valued measure. Then, for a fixed vertical load, the maximum value of the lateral load which is compatible with the equilibrium of the panel is determined.

The Interval Minimum Load Cutting Problem in the Process of Transmission Network Expansion Planning Considering Uncertainty in Demand

This paper studies the minimum load cutting problem existing in the process of transmission network expansion planning when load is uncertain and expressed in interval number. The interval most minimum load cutting model is established and can be solved to get the maximum value of the minimum load cutting number when load is interval uncertain. The solution can be used to evaluate the safety of the planning schemes under interval uncertainty and guide the new plans' making under interval load. The load values in the optimal solution of this problem have been proved to be at their lower or upper limits. Two different algorithms are proposed to solve this model. One is better in being capable of getting global optimal solution, while the other is better in calculation speed. Both of them are compared with two traditional methods that are generally used to evaluate the system's safety under uncertainty in aspects of precision and speed. This evaluation method is applied to the greedy randomized adaptive search procedure algorithm to solve the transmission expansion planning problem under interval load. The case results show the rightness and validity of the model and algorithms proposed in this paper.

In Vitro Fracture Resistance and Deflection of Pulpless Teeth Restored with Fiber Posts and Prepared for Veneers

The aim of this in vitro study was to evaluate the influence of endodontic therapy, veneer preparation, and their association on fracture resistance and deflection of pulpless anterior teeth and assess whether restoration with quartz fiber-reinforced post can influence these properties. Seventy-five freshly extracted human maxillary central incisors were selected. Teeth were randomly divided into 4 experimental groups (veneer preparation/endodontic therapy/endodontic therapy and veneer preparation/endodontic therapy, veneer preparation, and fiber post placement) and a control group ( n = 15). Specimens were loaded to fracture recording crown deflection under load, and data were statistically analyzed. Veneer preparations and endodontic treatment did not significantly influence fracture resistance of maxillary incisors. On the contrary, preparation for veneer significantly increased the deflection values of the specimens. Fiber post restorations seemed to significantly increase mean maximum load values for specimens prepared for veneers. A fiber-reinforced post restoration can be suggested when endodontic treatment is associated with veneer preparation.

The impact of loads on standard diameter, small diameter and mini implants: a comparative laboratory study

While caution in the use of small-diameter (< or = 3.5 mm) implants has been advocated in view of an increased risk of fatigue fracture under clinical loading conditions, a variety of implant designs with diameters < 3 mm are currently offered in the market for reconstructions including fixed restorations. There is an absence of reported laboratory studies and randomized-controlled clinical trials to demonstrate clinical efficacy for implant designs with small diameters. This laboratory study aimed to provide comparative data on the mechanical performance of a number of narrow commercially marketed implants. Implants of varying designs were investigated under a standardized test set-up similar to that recommended for standardized ISO laboratory testing. Implant assemblies were mounted in acrylic blocks supporting laboratory cast crowns and subjected to 30 degrees off-axis loading on an LRX Tensometer. Continuous output data were collected using Nexygen software. Load/displacement curves demonstrated good grouping of samples for each design with elastic deformation up to a point of failure approximating the maximum load value for each sample. The maximum loads for Straumann (control) implants were 989 N (+/-107 N) for the 4.1 mm RN design, and 619 N (+/-50 N) for the 3.3 mm RN implant (an implant known to have a risk of fracture in clinical use). Values for mini implants were recorded as 261 N (+/-31 N) for the HiTec 2.4 mm implant, 237 N (+/-37 N) for the Osteocare 2.8 mm mini and 147 N (+/-25 N) for the Osteocare mini design. Other implant designs were also tested. The diameters of the commercially available implants tested demonstrated a major impact on their ability to withstand load, with those below 3 mm diameter yielding results significantly below a value representing a risk of fracture in clinical practice. The results therefore advocate caution when considering the applicability of implants < or = 3 mm diameter. Standardized fatigue testing is recommended for all commercially available implants.

Characterising a historical bridge’s bricks in Popayán (Colombia)

This article presents the procedures and results of studying the physical-mechanical and chemical-mineralogical characterisation of the bricks originally used in a masonry arch bridge; the bridge was built in the first half of the 18th century in the city of Popayán, Colombia. Core-samples were thus extracted from the bridge’s lower area and subjected to different laboratory tests. Physical-mechanical characterisation quantified values related to dry weight, suspended weight, saturated weight, porosity, apparent gravity, apparent density and maximum load values, cold compression resistance and elasticity modulus. The results revealed the bricks’ high porosity and their low resistance to compression stress. Chemical-mineralogical characterisation involved a combination of tests including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red spectroscopy (FTIR). Several minerals found led to deducting the source of the raw material, as well as verifying some brick production characteristics of the time in the said region. Tridimite, cristobalite, magnetite and calcium carbonate were some of the phases formed by the temperatures reached while firing the bricks, while potassium sulphate presence in one of the samples conveyed the nature of the construction materials’ production characteristics. Combining XRD and XPS analysis provides information about firing temperature and the new mineralogical phases appearing at the end of this process; FTIR proved functional OH and Si-O-Si group presence. These bricks’ characteristics provided valuable data for restoration purposes, formulating a new brick from raw material complying with reconstruction requirements.

RANKL Inhibition with Osteoprotegerin Increases Bone Strength by Improving Cortical and Trabecular bone Architecture in Ovariectomized Rats

Ovariectomy (OVX) results in bone loss caused by increased bone resorption. RANKL is an essential mediator of bone resorption. We examined whether the RANKL inhibitor osteoprotegerin (OPG) would preserve bone volume, density, and strength in OVX rats. Rats were OVX or sham-operated at 3 mo of age. Sham controls were treated for 6 wk with vehicle (Veh, PBS). OVX rats were treated with Veh or human OPG-Fc (10 mg/kg, 2/wk). Serum RANKL and TRACP5b was measured by ELISA. BMD of lumbar vertebrae (L(1)-L(5)) and distal femur was measured by DXA. Right distal femurs were processed for bone histomorphometry. Left femurs and the fifth lumbar vertebra (L(5)) were analyzed by muCT and biomechanical testing, and L(6) was analyzed for ash weight. OVX was associated with significantly greater serum RANKL and osteoclast surface and with reduced areal and volumetric BMD. OPG markedly reduced osteoclast surface and serum TRACP5b while completely preventing OVX-associated bone loss in the lumbar vertebrae, distal femur, and femur neck. Vertebrae from OPG-treated rats had increased dry and ash weight, with no significant differences in tissue mineralization versus OVX controls. muCT showed that trabecular compartments in OVX-OPG rats had significantly greater bone volume fraction, vBMD, bone area, trabecular thickness, and number, whereas their cortical compartments had significantly greater bone area (p < 0.05 versus OVX-Veh). OPG improved cortical area in L(5) and the femur neck to levels that were significantly greater than OVX or sham controls (p < 0.05). Biomechanical testing of L(5) and femur necks showed significantly greater maximum load values in the OVX-OPG group (p < 0.05 versus OVX-Veh). Bone strength at both sites was linearly correlated with total bone area (r(2) = 0.54-0.74, p < 0.0001), which was also significantly increased by OPG (p < 0.05 versus OVX). OPG treatment prevented bone loss, preserved trabecular architecture, and increased cortical area and bone strength in OVX rats.

Studies on the biomechanics of the human clavicle (author's transl)

64 non preserved and 35 preserved clavicles were fractured in three defined positions in a bending test by a tension testing machine with electronic measurement of force. 30 non preserved bones were fractured in an axial infraction test. Force-deflection-diagrams were registered, and the values of maximum load, breaking load, ultimate deflection and energy were correlated to cross section and thickness of compacta. The significantly greater non preserved male clavicles are loadable at a higher level (medium breaking load about 1200 N) than female bones (medium breaking load abut 800 N). The breaking energy of the more flexible female clavicles is about 30% lower than those of males whereas elastic modulus of female clavicles is significant greater. Preservation has a significant influence on biomechanical properties of bones: ultimate deflection decreases; breaking energy, ultimate stress and elastic modulus increase. Breaking load is greatest in the middle portion of the clavicle, while deflection is greatest in the sternal portion. Removal of periosteum causes lower breaking load, deflection, ultimate stress and elastic modulus as well. With axial load clavicle fractures occur most frequently between middle and sternal third.

Efeitos mecânicos causados pela variação da inclinação do parafuso excêntrico no orifício da placa de autocompressão

OBJETIVO: Avaliar os efeitos mecânicos da inclinacao do parafuso excentrico sobre a compressao axial com placa. METODOS: Corpos de prova artificiais simulando fragmentos de osso diafisario foram fixados com placa DCP® de 4,5mm de sete orificios. Uma celula de carga registrou as forcas de compressao axial no intervalo entre os fragmentos. Guias de perfuracao excentrica com inclinacoes em relacao ao plano longitudinal e transversal da placa foram confeccionados para o experimento. A compressao foi medida em dois diferentes sitios do foco de fratura virtual. De acordo com a magnitude da inclinacao e sua direcao em relacao ao orificio da placa, oito diferentes grupos foram constituidos. Os ensaios mecânicos registraram a forca maxima e a forca maxima efetiva. RESULTADOS: A inclinacao do parafuso em direcao contraria a da rampa de deslizamento do orificio da placa foi acompanhada de diminuicao nos valores medios de forca maxima e forca maxima efetiva de compressao 0o > 10oi (p 20oi (p 25oi (p < 0,001). CONCLUSAO: Em modelo experimental, utilizando-se placas do tipo DCP® nao pre-tensionadas, a inclinacao na insercao de parafusos excentricos promoveu alteracoes nos valores medios da forca de compressao axial. Houve diferencas significativas (p < 0,05) para menos na compressao axial obtida na cortical subjacente a placa, quando da insercao de parafusos inclinados no plano longitudinal com direcao oposta a da rampa de deslizamento do orificio DCP®.

242 大型回転構造物の接触荷重同定法(OS9.逆問題解析手法の開発と最新応用(2),オーガナイズドセッション)

The support parts of large rotation structure like kiln furnace are given high load. The maximum value of the contact load fluctuates in the operation because the structure is rotated. Therefore, we need to examine the maximum load in the design of the large rotation structure. However, the load of support part is difficult to predict by some reasons. One reason is that the support part translates the load by contact and the load varies by location. The identification of the contact load at the support part is very important factor for the estimation of the large rotation structure. This paper investigates to identify the contact load at the support part in the large rotation structure. The applicability and the effectiveness of the method are conformed for kiln furnace of actual large rotation structure by inverse analysis using measuring data.

Deterioration of bone quality by long-term magnetic field with extremely low frequency in rats

The aim of our study was to investigate the effects of long-term (45 days) magnetic field (50 Hz, 1 mT; MF) on femur biomechanical parameters of rats. Bone mineral density (BMD) and histological investigation were also evaluated. For this purpose, twenty-four 8-week-old, Wistar–Albino female and male rats were assigned randomly to female control (FC) and MF-exposed rats (F-MF); male control (MC) and MF-exposed rats (M-MF). BMD was measured by dual-energy X-ray absorptiometry. Cross-sectional area of the femoral shaft was evaluated by computerized tomography. Biomechanical measurements were performed at the mid-diaphysis of the left femur with tensile test. Maximum load, displacement, stiffness, energy absorption capacity (structural properties); ultimate stress, ultimate strain, elastic modulus and toughness (material properties) were calculated. Diaphysial cortical bone thickness was measured by using histological method from the right femur. In respect to the cortical thickness of the rats' femurs, there was statistically significant interaction between the gender and group ( P < 0.05), while the BMD and cortical area were not ( P > 0.05). The BMD, cortical thickness and area values of the femurs of MF-exposed rats (F-MF, M-MF) were significantly decreased in comparison to that of the controls (FC, MC) ( P < 0.05). There were no statistically significant differences between the control and the MF-exposed rats in respect to the femur length ( P > 0.05). There were no statistically significant interaction between the gender and group with regard to the maximum load, displacement, stiffness, ultimate stress, ultimate strain, elastic modulus and toughness endpoints, while the energy absorption capacity was significant ( P < 0.05). Maximum load, displacement and stiffness values of MF-exposed rats were significantly decreased compared to that of the controls ( P < 0.05). Femurs of M-MF rats had less absorbed energy than that in controls ( P < 0.05). Ultimate stress and elastic modulus parameters were significantly decreased in MF-exposed rats in comparison to that of the controls ( P < 0.05). Ultimate strain was higher in MF-exposed rats than that in controls ( P > 0.05). The mean of toughness was decreased in MF-exposed rats compared to that of the controls ( P > 0.05). In conclusion, the bone quality of rats is decreased by magnetic field exposure.

Influence of Different Root Canal–Filling Materials on the Mechanical Properties of Root Canal Dentin

The aims of this study were to compare Resilon (Resilon Research LLC, Madison, CT) in conjunction with either a bonding (Epiphany; Pentron Clinical Technologies, Wallingford, CT) or a nonbonding endodontic sealer (Pulp Canal Sealer; Kerr Corporation, Orange, CA) to EndoRez (Ultradent Products Inc, South Jordan, UT) and gutta-percha with regards to the physical properties and flexural stress in standardized dentin cylinders and the flexural stress of Resilon and gutta-percha. The external surface of 50 maxillary central incisors was reduced by means of mechanical milling to obtain dentin cylinders with an external diameter of 3 mm and minimum length of 12 mm. Root canals were prepared to obtain a standardized cylindrical preparation of 1.3 mm in diameter at the center of the root. The cylinders were randomly divided into five groups (n = 10): group 1: obturation with gutta-percha and Pulp Canal Sealer; group 2: obturation with Resilon, Epiphany primer, and Epiphany; group 3: obturation with Resilon and Pulp Canal Sealer; group 4: obturation with EndoRez methacrylate-based endodontic sealer; and group 5: dentin cylinders were not obturated. Ten gutta-percha (group 6) and Resilon (group 7) pellets for the Obtura gun were also tested. A three-point bending test was used to measure the maximum load values of specimens from groups 1 to 5 and the flexural strength and flexural modulus values for specimens from groups 6 and 7. Statistical analysis was performed to determine significance differences (p < 0.05). An analysis of variance test showed no significant difference among groups 1 to 5 (p = 0.697; F = 0.60). An independent sample t test showed statistically significant differences between groups 6 and 7 in flexural strength (p = 0.000) and flexural modulus (p = 0.000). Within the limits of this study, it may be concluded that the currently available endodontic-filling materials and their recommended adhesive procedures are not able to influence the mechanical properties of root canal dentin and that the flexural properties of Resilon and gutta-percha are too low to reinforce roots.