Isaac Jamil Sayeg

In vitro analysis of the penetration of methylene blue dye in human radicular dentin using different methods of impregnation

The purpose of the present study was to verity whether different conditions of contact with a dye solution would result in different levels of the impregnation by the marker agent in human radicular dentin. The root canals of 60 upper human canines were immersed in methylene blue dye (0.5%, pH 7.0) for 24 h under six different conditions: passive immersion; pre-agitation for 10 min using an endodontic ultrasound; pre-agitation for 10 min using a cleaning ultrasound; 25-mmHg vacuum for 10 min followed by passive immersion; 30-mmHg and 650-mmHg vacuum for 24 h. The roots were longitudinally sectioned and dye impregnation was assessed by a trained and calibrated examiner, using the Q 550 IW image analyser (Leica Qwin, Cambridge, England). The measurements were analysed with anova and Tukey test. The results revealed no significant difference among the different methods for dye impregnation. In the cervical third, impregnation with 30 mmHg was significantly more effective than with endodontic ultrasound or 25 mmHg. At the apical third, no differences were observed between any of the dye impregnation methods. The comparison of different thirds revealed a statistically significant difference between the cervical and apical and the middle and apical thirds, but not between the cervical and middle thirds.

Purification and Characterization of a Natural Brazilian Clay Blend

Clay blends are products used in several industrial sectors, such as petrochemical or pharmaceutical. In this work we describe a natural clay blend occurring in northeastern Brazil. The aim was to purify and investigate their rheological and physical-chemical properties. Foster essays with water and organic solvents were utilized to access the swelling properties of the analyzed sample. Powder X-ray diffractograms (PXRD) were utilized to analyze qualitatively the clay minerals presents in the sample blend. Scanning eletronic microscopy (SEM) and Malvern techniques were used to investigate the sample clay morphology. The purification proceeding allowed separate distinct clay phases with different colors. PXRD analysis demonstrated that each clay phase presents similar structure. SEM and Malvern analysis showed distinct morphology and different size distribution for each clay phase. Our results revealed that the analyzed sample clay may be classified as smectite blend with strong potential for use in pharmaceutical and cosmetic products.

Effect of Passivation Treatments on the Corrosion Resistance of PIM 316L Stainless Steel in a PEM Fuel Cell Simulated Environment

In this work, the corrosion resistance of passivated PIM 316L stainless steel specimens was evaluated in 1M H2SO4 + 2 ppm HF solution at room temperature during 28 days of immersion. Passivation was carried out in HNO3 and H2SO4 solutions. The electrochemical behavior of the passivated specimens was assessed through electrochemical impedance spectroscopy and anodic polarization curves. Scanning electron microscopy (SEM) was employed to observe the surface of the specimens before and after the passivation treatments. The results pointed to a strong influence of the passivation conditions on the corrosion resistance of the specimens.