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Pekka K Vallittu - One of the best experts on this subject based on the ideXlab platform.
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effect of cross sectional design on the modulus of elasticity and toughness of fiber reinforced composite materials
Journal of Prosthetic Dentistry, 2005Co-Authors: Scott R Dyer, Lippo V J Lassila, Mikko Jokinen, Pekka K VallittuAbstract:Statement of problem Many current fabrication protocols for dental fiber-reinforced composites use hand lay-up techniques and technician design input. Little information exists regarding how the manipulation of the cross-sectional design of a prosthesis might affect the modulus of elasticity and toughness. Purpose The aim of this study was to determine the effect of simple and complex cross-sectional designs on the modulus of elasticity and toughness of fiber-reinforced composite used for dental prostheses. Material and methods Two particulate composites (BelleGlass HP and Targis) were reinforced with ultra-high–molecular-weight polyethylene fiber ribbon (Connect), woven E-glass fibers (Vectris Frame), or unidirectional R-glass fibers (Vectris Pontic). A range of fiber positions, orientations, or geometries were incorporated into the rhombic specimens (2 × 2 × 25 mm 3 ) to achieve simple and complex experimental cross-sectional designs. The control specimen did not contain fiber reinforcement. Specimens (n=6) were stored 1 week in distilled water at 37°C prior to 3-point load testing to determine the modulus of elasticity (GPa) and toughness (MPa). The data within each main fiber group were subjected to 1-way analysis of variance and a Tukey post hoc test (α=.05). Cross-sections of randomly selected test specimens (n=2) were made for scanning electron microscope (SEM) analysis of the fiber distribution. Results The mean modulus of elasticity varied from 8.7 ± 2.0 GPa (Targis control) to 21.6 ± 1.4 GPa (2 unidirectional glass fiber reinforcements, 1 each at the Tension Side and the compression Side). Mean toughness varied from 0.07 ± 0.02 MPa (unidirectional glass fiber positioned at the compression Side) as the lowest mean, to 4.53 ± 0.89 MPa (unidirectional glass fiber positioned at the Tension Side) as the highest. Significant differences were identified between specimen groups in each main category (all groups P P =.003). SEM micrographs showed fiber distribution in the cross section of test specimens to correspond with the intended fiber geometry. Conclusion The modulus of elasticity of the composite specimens increased when 1 or more glass fiber groups were located at the compression Side of the specimen. Toughness was most effectively increased when 1 or more fiber groups were located at the Tension Side of the specimen.
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flexural fatigue of denture base polymer with fiber reinforced composite reinforcement
Composites Part A-applied Science and Manufacturing, 2005Co-Authors: Katja K. Narva, Lippo V J Lassila, Pekka K VallittuAbstract:Abstract Flexural fatigue of denture base polymer with various fiber reinforcements was investigated. The test specimens (3×5×50 mm3, n=6) were made of autopolymerized polymethylmethacrylate (PMMA). The following fiber reinforcements, referred to as partial fiber reinforcements, were embedded into the denture base resin: ribbon polyethylene fibers, unidirectional dimethacrylate-impregnated glass fibers, dimethacrylate–PMMA-impregnated glass fibers and PMMA-preimpregnated glass fibers. Number of cycles to failure was measured in water by the constant deflection fatigue test with a maximum of 100,000 cycles of the test specimens with partial fiber reinforcement placed at various locations, namely, on the compression or Tension Side. Magnitude of deflection was 1 mm and loading frequency 2.0 Hz. The number of loading cycles needed to cause a fracture in the test specimen was conSidered the fatigue failure of the specimen. The results of this study suggest that the fiber reinforcements that allowed even fiber distribution in the cross-section or were placed on the tensile Side reinforced the test specimens of PMMA most effectively. The PMMA-preimpregnated glass–fiber reinforcements resulted in a higher number of loading cycles (maximum 100,000) than polyethylene fiber ribbon (2886 cycles in compression, 23,220 in Tension).
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effect of fiber position and orientation on fracture load of fiber reinforced composite
Dental Materials, 2004Co-Authors: Scott R Dyer, Lippo V J Lassila, Mikko Jokinen, Pekka K VallittuAbstract:Abstract Objectives. The aim of this study was to determine the effect of fiber position and orientation on the initial and final fracture loads of fiber-reinforced composite (FRC). Methods. Test specimens made of two indirect particulate composites (BelleGlass HP, Kerr, Orange, CA) or (Targis, Ivoclar Vivadent, Amherst, NY) were reinforced with ultra high molecular weight polyethylene (UHMWPE) fiber ribbon (Connect, Kerr, Orange, CA), woven E-glass fibers (Vectris Frame, Ivoclar Vivadent, Amherst, NY) or unidirectional R-glass fibers (Vectris Pontic, Ivoclar Vivadent, Amherst, NY). Fibers were placed with different positions, orientations or geometry into the rhombic test specimens (2×2×25 mm3). Control specimens did not contain fiber reinforcement. The test specimens (n=6) were stored in distilled water for 1 week at 37 °C before testing in a three-point loading test to determine the initial and final fracture load values. Results. Initial failure loads varied from 22.6 to 172.1 N. The lowest value resulted from one UHMWPE reinforcement fiber located in diagonal orientation and the highest from two unidirectional glass fiber reinforcements, one located on the Tension Side and the second on the compression Side. Significance. Position and fiber orientation influenced the load to initial and final failure, and specimen deflection. Tension Side reinforcement was most effective in increasing the load to initial and final fracture.
A J Comer - One of the best experts on this subject based on the ideXlab platform.
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analysis of failure modes for a non crimp basalt fiber reinforced epoxy composite under flexural and interlaminar shear loading
Composite Structures, 2020Co-Authors: Indraneel R Chowdhury, Niamh H Nash, Alexandre Portela, N P Odowd, A J ComerAbstract:Abstract This study investigates the mechanical properties (interlaminar shear and flexural strength) and failure modes of a basalt/epoxy composite, manufactured using a non-crimp-fabric (NCF) with a vacuum assisted resin infusion process. Under flexural bending, damage initiated on the compression Side between 20 and 50% of peak load and progressed from ply to ply with increasing load. Failure at the Tension surface of the flexural bending specimen was confined to the bottom ply and was evident only close to final failure. Fiber kinking was the dominant failure mechanism on the compression Side whereas fiber breakage was the dominant mechanism on the Tension Side. Regarding interlaminar shear, interlaminar shear cracks initiated once samples were subjected to stress levels above 50% of peak stress and grew until failure with the crack following the fibre matrix interface of 90° tows. Overall, comparing with values available in the open literature, the NCF basalt/epoxy composite outperformed plain-woven basalt/epoxy and plain-woven E-glass/epoxy composites in terms of both flexural and interlaminar shear strength but demonstrated lower strength than NCF E-glass/epoxy composite.
Jonas Thor Snaebjornsson - One of the best experts on this subject based on the ideXlab platform.
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strength and stiffness of glulam beams reinforced with glass and basalt fibres
Composites Part B-engineering, 2017Co-Authors: Eythor Rafn Thorhallsson, Gudmundur Ingi Hinriksson, Jonas Thor SnaebjornssonAbstract:Abstract Timber has throughout history played an important role in all kinds of construction work as it is easy to work with and has many advantages compared to alternative materials. Through engineered timber products such as glulam, the natural variability in material properties of timber has been reduced, providing stronger, stiffer and more reliable structural elements. In recent years' new techniques have emerged to enhance these properties even further by using FRP materials to strengthen structural timber components. The FRP materials have more tensile strength and higher modulus of elasticity than timber. In recent years' experiments have been conducted in the Structural and Composite Laboratory at Reykjavik University (SEL) in order to investigate the effect of strengthening glulam beams using FRP materials. In these experiments, 24 glulam beams (3,2 m long, 65 mm wide and 167 mm high) were tested. Half of the beams were in strength class GL32h and the second half were in strength class GL30c. The beams were tested in a four-point bending test. The beams were randomly divided into groups with 3 or 4 beams in each group. For each group the bottom laminate of the beams was reinforced with slack basalt fibres, slack glass fibres, pre-stressed basalt fibres or with no reinforcement for comparison. The pre-stressing of the basalt fibre layers was done through cambering, where the beam was cambered to the point where the stresses in the timber reached 90% of authorized stresses. The test results were compared with an analytical model to predict the moment capacity. The numerical model conSiders the linear elastic behaviour and the plastic behaviour of the timber under compression. The experimental results compare relatively well with the mathematical model. Strengthening glulam beams on the Tension Side with FRP materials increases bending stiffness and bending strength. Increased reinforcement ratio, in the form of additional fibre cloth layers, had a significant effect on both the strength and the stiffness. Pre-stressing the FRP provides additional strength and higher stiffness compared to slack FRP strengthening. Strengthening the glulam beams on the Tension Side allows a possible reduction of the cross-section or lower timber grade while maintaining the same bending strength and stiffness as for the unreinforced beam.
Noriyoshi Shimizu - One of the best experts on this subject based on the ideXlab platform.
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effects of low energy laser irradiation on bone remodeling during experimental tooth movement in rats
Lasers in Surgery and Medicine, 2000Co-Authors: Koichiro Kawasaki, Noriyoshi ShimizuAbstract:Background and Objective Low-energy laser irradiation has many anabolic effects such as the acceleration of bone formation. However, its effects on tooth movement, performed by bone resorption and formation, have not been well characterized. Study Design/Materials and Methods A total of 10 g of orthodontic force was applied to rat molars to cause experimental tooth movement. A Ga-Al-As diode laser was used to irradiate the area around the moved tooth, and after 12 days, the amount of tooth movement was measured. Calcein was injected subcutaneously to label the newly formed alveolar bone for quantitative analysis. Immunohistochemical staining of proliferating cell nuclear antigen was performed to evaluate cellular proliferation. TRAPase staining was also performed to facilitate the identification of osteoclasts. Results In the laser irradiation group, the amount of tooth movement was significantly greater (1.3-fold) than that of the nonirradiation group in the end of the experiment. The amount of bone formation and rate of cellular proliferation in the Tension Side and the number of osteoclasts in the pressure Side were all significantly increased in the irradiation group when compared with the nonirradiation group (P < 0.01). Conclusion These findings suggest that low-energy laser irradiation can accelerate tooth movement accompanied with alveolar bone remodeling. Lasers Surg. Med. 26:282–291, 2000 © 2000 Wiley-Liss, Inc.
Martha S Ribeiro - One of the best experts on this subject based on the ideXlab platform.
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effects of corticopuncture cp and low level laser therapy lllt on the rate of tooth movement and root resorption in rats using micro ct evaluation
Lasers in Medical Science, 2018Co-Authors: Selly Sayuri Suzuki, Aguinaldo S Garcez, Patricia Reese, Hideo Suzuki, Martha S Ribeiro, Won MoonAbstract:: The aim of this study was to compare the rate of tooth displacement, quantity of root resorption, and alveolar bone changes in five groups: corticopuncture (CP), low-level laser therapy (LLLT), CP combined with LLLT (CP + LLLT), control (C), and negative control (NC). A total of 60 half-maxilla from 30 male Wistar rats (10 weeks old) were divided randomly into five groups: three (CP, LLLT, and CP + LLLT) test groups with different stimulation for accelerated-tooth-movement (ATM), one control (C) group, and one negative control (NC) group with no tooth movement. Nickel-titanium coil springs with 50 g of force were tied from the upper left and right first molars to micro-implants placed behind the maxillary incisors. For the CP and CP + LLLT groups, two perforations in the palate and one mesially to the molars were performed. For the LLLT and CP + LLLT groups, GaAlAs diode laser was applied every other day for 14 days (810 nm, 100 mW, 15 s). The tooth displacements were measured directly from the rat's mouth and indirectly from microcomputer (micro-CT) tomographic images. Bone responses at the Tension and compression sites and root resorption were analyzed from micro-CT images. The resulting alveolar bone responses were evaluated by measuring bone mineral density (BMD), bone volume fraction (BV/TV), and trabecular thickness (TbTh). Root resorption crater volumes were measured on both compression and Tension Sides of mesial and distal buccal roots. The tooth displacement in the CP + LLLT group was the greatest when measured clinically, followed by the CP, LLLT, and control groups (C and NC), respectively (p <0.05). The tooth movements measured from micro-CT images showed statistically higher displacement in the CP and CP + LLLT groups compared to the LLLT and control groups. The BMD, BV/TV, and TbTh values were lower at the compression Side and higher at the Tension Side for all three test groups compared to the control group. The root resorption crater volume of the distal buccal root was higher in the control group, followed by CP, LLLT, and CP + LLLT, mostly at the compression site. Combining corticopuncture and low-level laser therapy (CP + LLLT) produced more tooth displacement and less root resorption at the compression Side. The combined technique also promoted higher alveolar bone formation at the Tension Side.
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low level laser therapy stimulates bone metabolism and inhibits root resorption during tooth movement in a rodent model
Journal of Biophotonics, 2016Co-Authors: Selly Sayuri Suzuki, Aguinaldo S Garcez, Hideo Suzuki, Won Moon, Edilson Ervolino, Martha S RibeiroAbstract:LLLT improves tooth movement via bone formation and bone resorption in a rat model. This study evaluated the biological effects of low-level laser therapy (LLLT) on bone remodeling, tooth displacement and root resorption, occurred during the orthodontic tooth movement. Upper first molars of a total of sixty-eight male rats were subjected to orthodontic tooth movement and euthanized on days 3, 6, 9, 14 and 21 days and divided as negative control, control and LLLT group. Tooth displacement and histomorphometric analysis were performed in all animals; scanning electron microscopy analysis was done on days 3, 6 and 9, as well as the immunohistochemistry analysis of RANKL/OPG and TRAP markers. Volumetric changes in alveolar bone were analyzed using MicroCT images on days 14 and 21. LLLT influenced bone resorption by increasing the number of TRAP-positive osteoclasts and the RANKL expression at the compression Side. This resulted in less alveolar bone and hyalinization areas on days 6, 9 and 14. LLLT also induced less bone volume and density, facilitating significant acceleration of tooth movement and potential reduction in root resorption beSides stimulating bone formation at the Tension Side by enhancing OPG expression, increasing trabecular thickness and bone volume on day 21. Taken together, our results indicate that LLLT can stimulate bone remodeling reducing root resorption in a rat model.