Similitud de la morfología y química elemental de los cementos tipo agregado de trióxido mineral y cemento Portland, mediante microscopia electrónica de barrido y espectroscopia de dispersión de electrones / Similarities of elemental chemistry and morphology of cements type mineral trioxide aggregate and Portland cement through the use of scanning electronic microscopy and electron dispersion spectroscopy

En la actualidad, los estudios acerca de la similitud entre el cemento Portland y los cementos tipo mineral de tri-oxi agregado han demostrado que estos compuestos presentan un desempeño análogo, ya que son elaborados con base en el cemento Portland. Con el objeto de verificar los componentes y porcentajes del cemento Portland y los cementos comerciales tipo agregado de trióxido mineral Pro-Root® blanco y Pro-Root® gris, Angelus® y CPM® se elaboraron cinco muestras de cada material de 8 x 4 mm y se les practicó un estudio de textura de superficie mediante microscopio electrónico de barrido y un análisis de espectrometría de energía dispersiva. Resultados: Los cementos mostraron gran similitud entre el cemento Portland y el agregado de trióxido mineral, sólo que en el agregado de trióxido mineral encontramos ausencia de Fe, Mg, Na y K, y en los cementos tipo agregado de trióxido mineral se encontró regularmente O, C, Si, Ca, Al, Cl y Bi; únicamente se detectó la presencia de Ba en el CPM®. Conclusiones: Encontramos gran similitud de los componentes químicos entre el cemento Portland y los cementos tipo agregado de trióxido mineral de todas las marcas comerciales.

Currently, studies on similarities among Portland cement and cements type mineral trioxide aggregate have shown that these compounds exhibit similar performance. This can be due to the fact that they are made based on Portland cement. With the aim of assessing percentages and components of Portland cement and commercial cements type mineral trioxide aggregate ProRoot® white and Pro-Root® grey, Angelus® and CPM®, five 8 x 4 mm samples of each material were processed. These samples were subjected to a study of surface texture. This study was conducted with the help of a scanning electron microscope as well as a energy dispersive spectrometry analysis. Results: Upon comparison, Portland cement and mineral trioxide aggregate cements showed great similarities. The main difference was than in mineral trioxide aggregate there was absence of Fe, Mg, Na and K; in mineral trioxide aggregate cements O, C, Si, Ca, Al, Cl and Bi were found regularly. Ba presence was only detected in CP®. Conclusions: The present study established the presence of great similarities among chemical components of Portland cement and mineral trioxide aggregate cements of all commercial brands.

The Application of "Series Experiments" in the Teaching of Elementary Chemistry / 中华医学教育探索杂志

In order to synthetically train students to do scientific researches independently,inspire their enthusiasm and go-aheadism about study,and improve the quality of experimental teaching,we have been exploring to update experimental content and reform experimental system for many years,and have commenced a number of "Series Experiments".The setup of"Series Experiments" which means several separate experiments are organized together by their internal relations has already showed us a favorable effect.