Examinando por Autor "Ossa A."

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    Contribution of Root Canal Treatment to the Fracture Resistance of Dentin
    (Elsevier Inc., 2019-01-01) Yan W.; Montoya C.; Øilo M.; Ossa A.; Paranjpe A.; Zhang H.; Arola D.D.; Yan W.; Montoya C.; Øilo M.; Ossa A.; Paranjpe A.; Zhang H.; Arola D.D.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
    Introduction: Although the strength and toughness of dentin decrease with age, no study has explored if restorative treatments are a contributing factor. Methods: Multiple extracted teeth were obtained from randomly selected donors and categorized according to donor age and prior root canal treatment. The microstructure and chemical composition of radicular dentin were evaluated using scanning electron microscopy and Raman spectroscopy, respectively, and the strength was evaluated in 4-point flexure to failure. Data were compared using the Student t test. Results: Dentin from the root canal–restored teeth exhibited significantly lower strength (P <.05) than tissue from age- and donor-matched unrestored tooth pairs. Although there was no significant difference in the mineral-to-collagen ratio between the 2 groups, dentin obtained from the root canal–treated teeth exhibited more extensive collagen cross-linking and lower tubule occlusion ratios than the unrestored tooth pairs. Conclusions: There is a decrease in the strength of radicular dentin with aging, but prior root canal treatment increases the extent of degradation. © 2018 American Association of Endodontists
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    Modeling and analysis of susceptibility to permanent deformation in asphalt mixtures
    (Pontificia Universidad Católica de Chile, 2011-01-01) Julián Vidal V.; Ossa A.; Julián Vidal V.; Ossa A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
    Perm. Deformation of Asphaltic Mixtures in the Metropol. Area of Valle de Aburra - Antioquia, Which Are Built under IVIAS' Specifications and Valle de Aburra, Were Studied by Employing A Constitutive Model Proposed Previously. This Model Had Proved to Be Effective in Predicting Deformations of Asphaltic Mixtures in the U. Kingdom under Different Kinds of Loads; under Uniaxial and Triaxial Conditions and Temperatures at Intervals between 0C and 40C. for the Specific Case of Valle de Aburra, Temperatures Ranged between 20C and 50C and the Model Was Implemented in Order to Predict Susceptibility to Perm. Deformation. by Means of An Exp. Stud. on Mixtures, It Was Found That Their Behav. under Steady State Condition Followed the Model Modified by Cross2, Thus Mixtures Showed A Visco-Lin. and Non-Lin. Behav. at Low and High Stress Levels, Respectively. It Was Observed That under Loading and Unloading Conditions, There Is A Temp. Dependence on the Mat. Behav., Which Was Properly Predicted by Arrhenius3 under the Studied Temperatures Interval. When Modeling Mixtures Behav., It Was Found That That Their Strain Susceptibility Varied Widely Depending on the Constituent Mat., Especially on the Aggregate, in Spite of the Fact That the Mixtures Are Similar.
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    Reduction in Fracture Resistance of the Root with Aging
    (Elsevier Inc., 2017-09-01) Yan W.; Montoya C.; Øilo M.; Ossa A.; Paranjpe A.; Zhang H.; Arola D.; Yan W.; Montoya C.; Øilo M.; Ossa A.; Paranjpe A.; Zhang H.; Arola D.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
    Introduction: The incidence of vertical root fracture in endodontically treated teeth increases with patient age. This study evaluated the microstructure, chemical composition, and mechanical properties of radicular dentin as a function of aging. Methods: Single-rooted teeth were obtained from adult donors ranging from age 15 to older than 80 years. Beams were extracted from the middle third of the root and subjected to 4-point flexure to failure to evaluate strength of dentin in terms of donor age. Based on the strength distribution, the fatigue strength of root tissue from young (<= 30 years) and old (>= 55 years) donor teeth was evaluated via cyclic flexure loading. The microstructure and chemical composition of radicular dentin from the 2 groups were evaluated as a function of distance from the root apex using microscopy and Raman spectroscopy, respectively. Results: The strength decreased with age by approximately 25 MPa per decade, which resulted in a significant difference (P <= .0001) between the young (199 +/- 36 MPa) and old (122 +/- 11 MPa) groups. There was also a significant difference (P <= .0001) in fatigue strength between the young and old age groups. Both the mineral-to-collagen ratio and degree of cross-linking increased with age, with the largest changes identified in the apical and middle thirds, respectively. Conclusions: There is a reduction in the damage tolerance of radicular dentin with increasing age. This degradation appears to result from changes in the microstructure, corresponding chemical composition, and increase in collagen cross-linking with age, and is most severe near the root apex.