4 research outputs found
Indicadores de riesgo a caries en pacientes de 3 a 12 años de edad que acuden a la clĂnica de la Especialidad en OdontopediatrĂa de la UAEM
La caries dental es un problema de salud pĂşblica por su alta prevalencia mundial. Existen mĂşltiples factores relacionados con su desarrollo, tales como higiene, nivel educativo de los padres, alimentaciĂłn, factores propios del huĂ©sped entre otros. El presente trabajo permite conocer los diferentes indicadores de riesgo a caries en los pacientes atendidos en la clĂnica de la Especialidad en odontopediatrĂa en la UAEM. Siendo estos los siguientes: edad, dolor dental previo, presencia de sĂndromes, tratamiento dental previo e higiene con ayuda como los más significativos
Improving the Surface Properties of an API 5L Grade B Pipeline Steel by Applying the Boriding Process. Part I: Kinetics and Layer Characterization
Although the use and promotion of renewable energies have increased in recent years, it is evident that the use of fossil fuels such as oil and gas continues to be of great importance. Likewise, pipelines are widely recognized as the most reliable and profitable means of transportation for liquid and gaseous hydrocarbons. Nevertheless, due to the nature of hydrocarbons, oil and gas pipelines are continually exposed to deterioration by corrosion and mechanical damage. In this context, this research focuses on the improvement of the surface properties of API 5L grade B pipeline steel by applying a surface hardening process. Samples of an API 5L grade B pipeline steel were exposed to boriding to form a layer of high hardness (from 2.60 GPa for the non-treated material to 14.12 GPa for the samples exposed to 1000 °C for 6 h). The treatment time was set at 2, 4, and 6 h, at temperatures of 850, 900, 950, and 1000 °C. Due to the saw-tooth morphology of the layers and the random nature of the process, it was possible to fit their thicknesses to a probability density function in all the experimental conditions. The crystalline structure of the layers was analyzed by X-ray diffraction and the morphology was observed using SEM and optical microscopy. The layer’s thickness ranged between 26.6 µm to 213.9 µm showing a close relationship with the experimental parameters of time and temperature. Finally, it is studied the changes undergone in the pipeline steel after the thermochemical process, observing an increase in the grain size as a function of the temperature
Improving the Surface Properties of an API 5L Grade B Pipeline Steel by Applying the Boriding Process—Part II: On the Changes in the Mechanical Properties
The mechanical performance of API 5L grade B steel, after undergoing a thermochemical boriding process, was assessed. We quantified the boride layer microhardness over cross-section specimens, with the aim of characterizing the mechanical resistance under different conditions. The pipeline steel was analyzed because of the changes in yield strength, ultimate tensile strength, and ductility after treatment with boron. These oil and gas pipelines must work in aggressive environments, so borided pipeline steel specimens were tested to assess their erosion–corrosion resistance. Another important characteristic to evaluate was the wearing resistance, because the pipelines tend to suffer scratches when they are under construction. We also present a discussion of the results of the total research work (Part I and Part II), including the results of the boride layer characterization as well as the changes in the substrate, with the goal of selecting the best conditions under which to treat pipeline steel. More extreme treatment conditions can help to form more stable and resistant boride layers, but they can considerably modify some mechanical characteristics of the API 5L grade B steel. For this reason, the boriding treatment conditions must be chosen in a synergistic way
Traumatismo dental en pacientes pediátricos que acuden a una clĂnica universitaria de odontopediatrĂa: un análisis retrospectivo de historias clĂnicas
Objetivo: Determinar la prevalencia de traumatismos dentales en los pacientes que acuden a una clĂnica de Especialidad en OdontopediatrĂa.
Materiales y MĂ©todos: Se realizĂł un estudio transversal retrolectivo, se incluyeron 309 expedientes clĂnicos de pacientes de 2 a 12 años de edad que acudieron para su atenciĂłn a la clĂnica de la Especialidad de OdontopediatrĂa de una universidad pĂşblica en Toluca, MĂ©xico. La variable dependiente fue la prevalencia de traumatismo dental. Las variables independientes incluidas en el estudio fueron: edad del paciente y sexo. El análisis estadĂstico se realizĂł utilizando pruebas no paramĂ©tricas en Stata 11.
Resultados: El promedio de edad fue de 5.71±2.43 años y el 50.8% fueron hombres. La prevalencia de traumatismo dental previo al estudio fue de 12.0% (IC 95% = 8.3 – 15.6). En el análisis bivariado, a pesar de que los varones presentaron una prevalencia de traumatismo dental de 14.0% y entre las mujeres fue de 9.9%, estas diferencias no fueron estadĂsticamente significativas (p=0.262). Se observĂł que los niños con traumatismo dental fueron más pequeños (promedio de edad = 4.74±1.86) que los que no presentaron traumatismo dental (promedio de edad = 5.84±2.47) (p=0.0166). Al realizar la prueba de tendencia no paramĂ©trica se notĂł que la disminuciĂłn de la prevalencia de traumatismo dental fue significativa (p=0.026).
Conclusiones: La prevalencia de traumatismo dental en esta muestra de niños fue de 12%. No se observó diferencia por sexo. Los más pequeños presentaron más traumatismo dental que los más grandes.
Correspondencia: Carlo Eduardo Medina-SolĂs; Correo: [email protected]
Conflicto de interés: Los autores declaran no tener conflicto de intereses.
Recibido: 27/10/2018; Aceptado: 22/11/201