The post core system has been used for reconstructon of severely damaged crown by caries or trauma.But problems such as crown exfoliation,post core fracture and root fracture have been reported. Ideal mechanical properties of the post require high fracture strength,high elastic limit and high resistance against fatigue and corrosion.Modulus of elasticity of the post should be similar with that of dentine.Low hardness is also required for the convenience of post removal in failure.Furthermore, the post itself must be translucent for the esthetical purpose.Several types of the post have been developed to satisfy the criteria above mentioned. The purpose of this study was to find out the mechanical properties of quartz fiber post by comparing with those of gold post and zirconia post. The results of this study were as follows : 1.Maximal fracture strength and stiffness of quartz fiber post were similar with those of gold post and zirconia post. 2.Young's modulus and hardness of quartz fiber post were lower than those of gold post and zirconia post. Mechanical property of quartz fiber post against post fracture was similar with that of gold post and zirconia post.Mechanical property of quartz fiber post against root fracture was higher than that of gold post and zirconia post.Quartz fiber post could be removed easily due to low hardness.
Crowns ; Elastic Modulus ; Elasticity ; Fatigue ; Hardness ; Quartz*

To demonstrate the stimulation effect on fracture healing by capacitively coupled electrical field, the rabbits' fibulae were fractured and treated with a capacitively coupled electrical signal (10V peak to peak, 60 kiloherz, symmetrical quadriangular wave) that was applied non-invasively over the skin surface overlying the approximate site of the fractured fibulae. Each fibula was evaluated with gross, roentgenographic, histological and mechanical tests after 21 days of the electrical stimulation, and compared to control group statistically. Maximum bending moment, Young's modulus of elasticity and bending stiffness were calculated by 3 point bending test, and the ratios of the fractured to the intact fibulae of the electrically stimulated rabbits were compared to the non-stimulated rabbits statistically. The results revealed that the fractured fibulae exposed to capacitively coupled electrical field showed the higher degree of fracture healing than the non-stimulated fibulae.
Elastic Modulus ; Elasticity ; Electric Stimulation ; Fibula ; Fracture Healing ; Rabbits ; Skin

The purpose of this study was to evaluate and compare the effect of the variable factors of wire on the elastic properties of looped rectangular wire. Five variable factors were presented - material(Hi-T, blue Elgiloy), wire size(.016" x .022", .018" x .025"), loop length(15mm, 20mm), loop configuration(open loop, closed loop), gabling (non-gable, gable). So, the total 256 specimens were divided into 32 groups, and each of those was pulled on Instron testing machine. The load-deflection curve of each wire was obtained, from which force, range in elastic limit, and stiffness were computed and analyzed statistically. The results were obtained as follows: 1. All of the variable factors - wire material, size, loop length, loop configuration, and gabling - took a significant effect on load-deflection rate of looped wire. 2. The force at elastic limit was the smallest in the group of Hi-T, .0l6"x.022", 20mm loop length, open loop, non-gable, and the largest in the group of blue Elgiloy, .018"x.025", 15mm loop length, closed loop, non-gable. 3. The range at elastic limit was the smallest in the group of Hi-T, .0l8"x.025", 15mm loop length, open loop, non-gable, and the largest in the group of HI-T, .016"x.022", 20mm loop length, closed loop, gable. 4. Loop configuration and loop length were the most effective factors on the elastic properties of looped wires, and gabling was the least effective.
Elasticity

Ultrasound (US) elastography is a tool that indicates the hardness of a lesion. Recent studies using elastography with freehand compression have shown similar diagnostic performance to conventional US in differentiating benign lesions from malignant breast masses. On the other hand, the acquired information is not quantitative, and the reliability of the imaging technique to correctly compress the tissue depends on the skill of the operator, resulting in substantial interobserver variability during data acquisition and interpretation. To overcome this, shear wave elastography was developed to provide quantitative information on the tissue elasticity. The system works by remotely inducing mechanical vibrations through the acoustic radiation force created by a focused US beam. This review discusses the principles and examination techniques of the two types of elastography systems and provides practical points to reduce the interobserver variability or errors during data acquisition and interpretation.
Acoustics ; Breast ; Breast Neoplasms ; Elastic Modulus ; Elasticity ; Elasticity Imaging Techniques ; Hand ; Hardness ; Observer Variation ; Vibration

This review aimed to describe the state of the art in muscle-tendon unit (MTU) assessment by supersonic shear wave imaging (SSI) elastography in states of muscle contraction and stretching, during aging, and in response to injury and therapeutic interventions. A consensus exists that MTU elasticity increases during passive stretching or contraction, and decreases after static stretching, electrostimulation, massage, and dry needling. There is currently no agreement regarding changes in the MTU due to aging and injury. Currently, the application of SSI for the purpose of diagnosis, rehabilitation, and physical training remains limited by a number of issues, including the lack of normative value ranges, the lack of consensus regarding the appropriate terminology, and an inadequate understanding of the main technical limitations of this novel technology.
Aging ; Consensus ; Diagnosis ; Elastic Modulus ; Elasticity ; Elasticity Imaging Techniques* ; Massage ; Muscle Contraction ; Muscle Stretching Exercises ; Rehabilitation ; Ultrasonography

PURPOSE: To evaluate and compare the performance of shear-wave elastography (SWE) for breast masses using the local shear wave speed (m/sec) vs. Young modulus (kPa). METHODS: A total of 130 breast lesions in 123 women who underwent SWE before ultrasound-guided core needle biopsy or surgical excision were included. With the region-of-interest placed over the stiffest areas of the lesion on SWE, the quantitative mean, maximum, and standard deviation (SD) of the elasticity values were measured in kPa and m/sec for each lesion. The SD was also measured with the region-of-interest including the whole breast lesion (wSD). The area under the receiver operating characteristic curve (AUC), sensitivity, and specificity of each elasticity value measured in kPa and m/sec were compared. RESULTS: Of the 130 lesions, 49 (37.7%) were malignant and 81 (62.3%) were benign. The AUCs for the mean, maximum, and SD of the elasticity values using kPa and m/sec did not differ significantly: mean, 0.974 vs. 0.974; maximum, 0.960 vs. 0.976; SD, 0.916 vs. 0.916. However, the AUC for wSD showed a significant difference: 0.964 (kPa) vs. 0.960 (m/sec) (P=0.036). There was no significant difference in the sensitivity and specificity of the mean, maximum, and wSD of the elasticity values. However, the specificity of the SD was significantly different between the two different measurements: 95.1% (kPa) vs. 87.7% (m/sec) (P=0.031). CONCLUSION: The quantitative elasticity values measured in kPa and m/sec on SWE showed good diagnostic performance. The specificity of the SD and AUC of the wSD measured in kPa were significantly higher than those measured in m/sec.
Area Under Curve ; Biopsy, Large-Core Needle ; Breast* ; Elastic Modulus* ; Elasticity ; Elasticity Imaging Techniques* ; Female ; Humans ; ROC Curve ; Ultrasonography, Mammary

This paper describes a liver elasticity and viscosity measurement system based on existing medical ultrasound platforms. This system relies on acoustic radiation force to invoke transient response on soft tissue, and employs displacement estimation algorithms to detect the propagation of shear wave. The research proves that the velocity of the shear wave may serve as a reliable estimation of the Young's modulus and viscosity coefficient of the liver tissue, and existing commercial products may be easily adapted to support this technique without extra hardware cost.
Algorithms ; Animals ; Elastic Modulus ; Elasticity Imaging Techniques ; instrumentation ; methods ; Liver Cirrhosis ; diagnostic imaging ; Viscosity

PURPOSE: To measure bending stiffness of rod in pedicle screw systems and identify the optimal rod for surgical correction of spinal deformities. MATERIALS AND METHODS: Bending stiffness of six different rods -7 mm stainless steel, 6 mm titanium alloy, 6.35 mm titanium, 5.5 mm titanium, 6 mm Shape Memory Alloy after martensite temperature, 7 mm Shape Memory Alloy after martensite temperature were measured by MTS 858 Bionix test system according to the ASTM standards. The specimen number was 8 for each rod. Young's modulus of elasticity was calculated from load-displacement data. RESULTS: Seven-mm stainless steel rod was stiffer than any other rods with bending stiffness of 143.7 +/- 3.8 N/mm, and also showed largest Young's modulus of elasticity of 135.1 +/- 3.0 GPa. Six-mm Shape Memory Alloy rod after martensite temperature was most flexible with bending stiffness of 58.1 +/- 2.8 N/mm, and showed smallest Young's modulus of elasticity of 68.0 +/-2.1 GPa. Seven-mm Shape Memory Alloy rod after martensite temperature was similar to the 6.35 mm titanium and 6 mm titanium alloy rod in bending stiffness and Young's modulus of elasticity. CONCLUSION: Seven-mm stainless steel rod was the stiffest rod tested, which is necessary to improve correction rate and maintain achieved correction. However, the rod selection should be individulized since stiffer rod might increase the chance of acute failure. Seven-mm Shape Memory Alloy could be more useful in deformity correction than 6 mm Shape Memory Alloy since it was not only similar to other rods in stiffness but also had shape memory function which would be necessary to establish the desired position of the spine.
Alloys ; Congenital Abnormalities ; Elastic Modulus ; Elasticity ; Memory ; Spine ; Stainless Steel ; Titanium

It is difficult to test the elastic modulus of the soft bio-anthropomorphic materials by using the general stretch-strain test method. With the equipment for a hardness testing system of bio-anthropomorphic materials and millesimal gauge, we introduce in this paper a compress-strain test method and carry out the related test-data curve-fitness. The test results indicate that this kind of method can be adopted in testing the elastic modulus of the soft bio-anthropomorphic materials and help to compare and distinguish the biomechanics equivalent between the tissues.
Biocompatible Materials ; Biomedical Engineering ; methods ; Computer Simulation ; Elastic Modulus ; Elasticity ; Hardness ; Humans ; Materials Testing ; methods

The requirements of orthodontic wire should include chemical stability, non-discoloration and non-corrosion in oral environment. Ability to be soldered, ease of fabrication and elasticity should be also considered. The purpose of this study was to compare and analyze the physical properties of Tru-chrome. The results were as follows: 1. Tru-chrome wire and E.S.S. wire were SUS 304 which was 18 Cr-8Ni austenite stainless steel. There was not significant difference in each composition between two wires. 2. There were not significant differences in ultimate tensile strength, yield strength, elongation and modulus of elasticity between Tru-chrome and E.S.S. wires. 3. There was not significant difference between flexure modulus of elasticity of Tru-chrome and E.S.S. wires. 4. Micro-hardness value of E.S.S. wire was more than that of Tru-chrome wire and they were softened significantly by solution heat reatment. 5. Micro-structure of Tru-chrome and E.S.S, wires showed fibrous interlocking grains, and an austenite structure after solution heat treatment. 6. There was significant difference between corrosion rate of Tru-chrome and E.S.S wires.
Edible Grain ; Corrosion ; Elastic Modulus ; Elasticity ; Hot Temperature ; Orthodontic Wires ; Stainless Steel* ; Tensile Strength