The Experts below are selected from a list of 88599 Experts worldwide ranked by ideXlab platform
J H Kinney - One of the best experts on this subject based on the ideXlab platform.
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age related transparent root Dentin mineral concentration crystallite size and mechanical properties
Biomaterials, 2005Co-Authors: J H Kinney, John A. Pople, Ravi K Nalla, T M Breunig, R O RitchieAbstract:Many fractures occur in teeth that have been altered, for example restored or endodontically repaired. It is therefore essential to evaluate the structure and mechanical properties of these altered Dentins. One such altered form of Dentin is transparent (sometimes called sclerotic) Dentin, which forms gradually with aging. The present study focuses on differences in the structure and mechanical properties of normal versus transparent Dentin. The mineral concentration, as measured by X-ray computed microtomography, was significantly higher in transparent Dentin, the elevated concentration being consistent with the closure of the tubule lumens. Crystallite size, as measured by small angle X-ray scattering, was slightly smaller in transparent Dentin, although the importance of this finding requires further study. The elastic properties were unchanged by transparency; however, transparent Dentin, unlike normal Dentin, exhibited almost no yielding before failure. In addition, the fracture toughness was lowered by roughly 20% while the fatigue lifetime was deleteriously affected at high stress levels. These results are discussed in terms of the altered microstructure of transparent Dentin.
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collagen orientation and crystallite size in human Dentin a small angle x ray scattering study
Calcified Tissue International, 2001Co-Authors: J H Kinney, John A. Pople, G W Marshall, Sally J. MarshallAbstract:The mechanical properties of Dentin are largely determined by the intertubular Dentin matrix, which is a complex composite of type I collagen fibers and a carbonate-rich apatite mineral phase. The authors perform a small angle x-ray scattering (SAXS) study on fully mineralized human Dentin to quantify this fiber/mineral composite architecture from the nanoscopic through continuum length scales. The SAXS results were consistent with nucleation and growth of the apatite phase within periodic gaps in the collagen fibers. These mineralized fibers were perpendicular to the Dentinal tubules and parallel with the mineralization growth front. Within the plane of the mineralization front, the mineralized collagen fibers were isotropic near the pulp, but became mildly anisotropic in the mid-Dentin. Analysis of the data also indicated that near the pulp the mineral crystallites were approximately needle-like, and progressed to a more plate-like shape near the Dentino-enamel junction. The thickness of these crystallites, {approx} 5 nm, did not vary significantly with position in the tooth. These results were considered within the context of Dentinogenesis and maturation.
Junji Tagami - One of the best experts on this subject based on the ideXlab platform.
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Characterization of transparent Dentin in attrited teeth using optical coherence tomography
Lasers in Medical Science, 2015Co-Authors: Mona M. Mandurah, Alireza Sadr, Turki A. Bakhsh, Yasushi Shimada, Yasunori Sumi, Junji TagamiAbstract:Attrition and wear of tooth surface occur with aging and result in loss of enamel, with exposure and histological changes in Dentin. Dealing with attrited teeth and restoration of the lost tissue are clinically challenging. The main objective of this study is to characterize the exposed transparent Dentin in the occlusal surface of attrited teeth by optical coherence tomography (OCT). Naturally attrited, extracted human teeth with occlusal-transparent Dentin were investigated in comparison to sound and carious teeth. The teeth were subjected to OCT imaging and then cross-sectioned and polished. OCT B-scans were compared to light microscopy images of the same cross section. In OCT images, some changes were evident at the transparent Dentin in attrited teeth. An OCT attenuation coefficient parameter ( μ _t) was derived based on the Beer-Lambert law as a function of backscatter signal slope. The mean values of μ _t were 1.05 ± 0.3, 2.23 ± 0.4, and 0.61 ± 0.27 mm^−1 for sound, carious, and transparent Dentins, respectively. One-way ANOVA with Tukey’s post-hoc showed a significant difference between groups ( p
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Age-related changes in hardness and modulus of elasticity of Dentine.
Archives of oral biology, 2006Co-Authors: Pisol Senawongse, Masayuki Otsuki, Junji Tagami, Ivar A. MjörAbstract:Summary Objectives Little knowledge has been clarified about the relationship between the morphological and physical changes of Dentine during aging. The purpose of this study was to clarify the modulus of elasticity and hardness related to the morphological changes of Dentine by aging using a transmitted light microscope (TLM) and a nano-hardness tester (NHT). Methods Aged human molars and young third molars were used. The Dentine morphology was observed under a TLM. The hardness and Young's modulus of elasticity related to the morphologic study were evaluated with an NHT. Results The thickness of mantle Dentine and globular Dentine of aged teeth were less than that of young teeth. Transparent Dentine was observed only underneath the attrition of young teeth. Reactionary tertiary Dentine formed and a “dark zone” was found at the junction between physiologic secondary and reactionary Dentine only in aged teeth. At the mantle Dentine, hardness and modulus of elasticity of aged Dentine were higher than those of young Dentine. The reactionary Dentine in aged teeth and newly developed secondary Dentine in young teeth demonstrated lower modulus of elasticity and hardness than those of other circumpulpal Dentine. Relatively low modulus of elasticity and hardness were observed at the zone between secondary and reactionary Dentine. Conclusions Changes in Dentine due to aging resulted in transformation of morphological features causing changes to their hardness and modulus of elasticity at the explicit areas such as the increase of hardness and modulus of elasticity at mantle Dentin and the reduction of these properties at the “dark zone” that found in aged teeth.
John A. Pople - One of the best experts on this subject based on the ideXlab platform.
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age related transparent root Dentin mineral concentration crystallite size and mechanical properties
Biomaterials, 2005Co-Authors: J H Kinney, John A. Pople, Ravi K Nalla, T M Breunig, R O RitchieAbstract:Many fractures occur in teeth that have been altered, for example restored or endodontically repaired. It is therefore essential to evaluate the structure and mechanical properties of these altered Dentins. One such altered form of Dentin is transparent (sometimes called sclerotic) Dentin, which forms gradually with aging. The present study focuses on differences in the structure and mechanical properties of normal versus transparent Dentin. The mineral concentration, as measured by X-ray computed microtomography, was significantly higher in transparent Dentin, the elevated concentration being consistent with the closure of the tubule lumens. Crystallite size, as measured by small angle X-ray scattering, was slightly smaller in transparent Dentin, although the importance of this finding requires further study. The elastic properties were unchanged by transparency; however, transparent Dentin, unlike normal Dentin, exhibited almost no yielding before failure. In addition, the fracture toughness was lowered by roughly 20% while the fatigue lifetime was deleteriously affected at high stress levels. These results are discussed in terms of the altered microstructure of transparent Dentin.
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collagen orientation and crystallite size in human Dentin a small angle x ray scattering study
Calcified Tissue International, 2001Co-Authors: J H Kinney, John A. Pople, G W Marshall, Sally J. MarshallAbstract:The mechanical properties of Dentin are largely determined by the intertubular Dentin matrix, which is a complex composite of type I collagen fibers and a carbonate-rich apatite mineral phase. The authors perform a small angle x-ray scattering (SAXS) study on fully mineralized human Dentin to quantify this fiber/mineral composite architecture from the nanoscopic through continuum length scales. The SAXS results were consistent with nucleation and growth of the apatite phase within periodic gaps in the collagen fibers. These mineralized fibers were perpendicular to the Dentinal tubules and parallel with the mineralization growth front. Within the plane of the mineralization front, the mineralized collagen fibers were isotropic near the pulp, but became mildly anisotropic in the mid-Dentin. Analysis of the data also indicated that near the pulp the mineral crystallites were approximately needle-like, and progressed to a more plate-like shape near the Dentino-enamel junction. The thickness of these crystallites, {approx} 5 nm, did not vary significantly with position in the tooth. These results were considered within the context of Dentinogenesis and maturation.
R O Ritchie - One of the best experts on this subject based on the ideXlab platform.
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age related transparent root Dentin mineral concentration crystallite size and mechanical properties
Biomaterials, 2005Co-Authors: J H Kinney, John A. Pople, Ravi K Nalla, T M Breunig, R O RitchieAbstract:Many fractures occur in teeth that have been altered, for example restored or endodontically repaired. It is therefore essential to evaluate the structure and mechanical properties of these altered Dentins. One such altered form of Dentin is transparent (sometimes called sclerotic) Dentin, which forms gradually with aging. The present study focuses on differences in the structure and mechanical properties of normal versus transparent Dentin. The mineral concentration, as measured by X-ray computed microtomography, was significantly higher in transparent Dentin, the elevated concentration being consistent with the closure of the tubule lumens. Crystallite size, as measured by small angle X-ray scattering, was slightly smaller in transparent Dentin, although the importance of this finding requires further study. The elastic properties were unchanged by transparency; however, transparent Dentin, unlike normal Dentin, exhibited almost no yielding before failure. In addition, the fracture toughness was lowered by roughly 20% while the fatigue lifetime was deleteriously affected at high stress levels. These results are discussed in terms of the altered microstructure of transparent Dentin.
Mona M. Mandurah - One of the best experts on this subject based on the ideXlab platform.
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Characterization of transparent Dentin in attrited teeth using optical coherence tomography
Lasers in Medical Science, 2015Co-Authors: Mona M. Mandurah, Alireza Sadr, Turki A. Bakhsh, Yasushi Shimada, Yasunori Sumi, Junji TagamiAbstract:Attrition and wear of tooth surface occur with aging and result in loss of enamel, with exposure and histological changes in Dentin. Dealing with attrited teeth and restoration of the lost tissue are clinically challenging. The main objective of this study is to characterize the exposed transparent Dentin in the occlusal surface of attrited teeth by optical coherence tomography (OCT). Naturally attrited, extracted human teeth with occlusal-transparent Dentin were investigated in comparison to sound and carious teeth. The teeth were subjected to OCT imaging and then cross-sectioned and polished. OCT B-scans were compared to light microscopy images of the same cross section. In OCT images, some changes were evident at the transparent Dentin in attrited teeth. An OCT attenuation coefficient parameter ( μ _t) was derived based on the Beer-Lambert law as a function of backscatter signal slope. The mean values of μ _t were 1.05 ± 0.3, 2.23 ± 0.4, and 0.61 ± 0.27 mm^−1 for sound, carious, and transparent Dentins, respectively. One-way ANOVA with Tukey’s post-hoc showed a significant difference between groups ( p