Accuracy of Microcomputed Tomography in Detecting Dentinal Cracks: A Correlative Study with Scanning Electron and Operative Microscopy.

The aim of the study was to evaluate the accuracy of microcomputed tomography (mCT) to detect dentinal cracks when compared with scanning electron microscopy (SEM) and operating microscopy (OM). Different conditions of pixel size (10 or 17 µm), sample moisture (dry/moist), and transillumination (with/without) were evaluated. Additionally, the influence of the dentinal defect width on its detection was analyzed. The root canals of human mandibular incisors were prepared with the Reciproc R40 instrument (VDW, Munich, Germany). The roots were sectioned 5 and 10 mm from the apex, and mCT scans of middle and apical segments were performed at two pixel sizes: 10 µm and 17 µm, under dry and moist conditions (groups: 10dry, 10moist, 17dry, and 17moist). The operating microscope was used with and without transillumination (groups: OMTrans and OM). Findings showed that accuracy was moderate for the 10dry, 10moist, and OMTrans groups, poor for OM and very poor for 17dry and 17moist. The thickness of the dentin crack significantly influenced its detection by mCT using the resolution of 10 µm in both dry and wet conditions (P = .002), 17 µm in the dry condition (P = .002), and by the operating microscope using transillumination (P = .009). Some cracks visualized in SEM were not detected by mCT and an operating microscope. Not only the mCT resolution but also the sample moisture condition and the dentinal crack width can significantly influence its detection.

Comparison of antibacterial activity of alexidine alone or as a final irrigant with sodium hypochlorite and chlorhexidine.

AIMS: To compare the antibacterial activity of alexidine (ALX) alone or as a final irrigant in combination with sodium hypochlorite (NaOCl), with the most common canal irrigants, NaOCl and chlorhexidine (CHX). MATERIALS AND METHODS: Ninety-four root fragments from extracted human teeth were infected with Enterococcus faecalis for 24 h and then distributed into 4 groups of 20 fragments each. The NaOCl, CHX and ALX groups were immersed in 1 ml of 2.5% NaOCl, 2% CHX, and 1% ALX for 10 min, respectively. The samples of the NaOCl+ALX group were immersed in 1 ml of 2.5% NaOCl for 10 min followed by 1% ALX for 10 min. Bacteriological samples were taken, cultured, and the colony-forming units were counted. RESULTS: There was no significant differences among the experimental groups (P>0.05) except for the comparisons CHX versus ALX and NaOCl+ALX versus ALX (P=0.004). ALX alone was the worst irrigant. CHX and NaOCl+ALX eradicated all bacteria. All experimental groups were significantly more effective than the control group immersed in saline (P<0.05). CONCLUSIONS: The antibacterial effect of ALX alone was inferior to 2% CHX and 2.5% NaOCl. However, the combination of NaOCl with ALX as a final irrigant eradicated the biofilms.

Streptococcus pneumoniae resists intracellular killing by olfactory ensheathing cells but not by microglia.

Olfactory ensheathing cells (OECs) are a type of specialized glial cell currently considered as having a double function in the nervous system: one regenerative, and another immune. Streptococcus pneumoniae is a major agent of severe infections in humans, including meningitis. It is commonly found in the nasopharynx of asymptomatic carriers, and, under certain still unknown conditions, can invade the brain. We evaluated whether pneumococcal cells recovered from lysed OECs and microglia are able to survive by manipulating the host cell activation. An intracellular-survival assay of S. pneumoniae in OECs showed a significant number of bacterial CFU recovered after 3 h of infection. In contrast, microglia assays resulted in a reduced number of CFU. Electron-microscopy analysis revealed a large number of pneumococci with apparently intact morphology. However, microglia cells showed endocytic vesicles containing only bacterial cell debris. Infection of OEC cultures resulted in continuous NF-κB activation. The IFN-γ-induced increase of iNOS expression was reversed in infected OECs. OECs are susceptible to S. pneumoniae infection, which can suppress their cytotoxic mechanisms in order to survive. We suggest that, in contrast to microglia, OECs might serve as safe targets for pneumococci, providing a more stable environment for evasion of the immune system.

Extracellular ATP induces cell death in human intestinal epithelial cells.

BACKGROUND: Extracellular ATP is an endogenous signaling molecule released by various cell types and under different stimuli. High concentrations of ATP released into the extracellular medium activate the P2X7 receptor in most inflammatory conditions. Here, we seek to characterize the effects of ATP in human intestinal epithelial cells and to evaluate morphological changes in these cells in the presence of ATP. METHODS: We treated human intestinal epithelial cells with ATP and evaluated the effects of this nucleotide by scanning and transmission electron microscopy analysis and calcium measurements. We used flow cytometry to evaluate apoptosis. We collected human intestinal explants for immunohistochemistry, apoptosis by the TUNEL approach and caspase-3 activity using flow cytometry analyses. We also evaluated the ROS production by flow cytometry and NO secretion by the Griess technique. RESULTS: ATP treatment induced changes characteristic of cell death by apoptosis and autophagy but not necrosis in the HCT8 cell line. ATP induced apoptosis in human intestinal explants that showed TUNEL-positive cells in the epithelium and in the lamina propria. The explants exhibited a significant increase of caspase-3 activity when the colonic epithelial cells were incubated with IFN-gamma followed by ATP as compared to control cells. In addition, it was found that antioxidants were able to inhibit both the ROS production and the apoptosis induced by ATP in epithelial cells. GENERAL SIGNIFICANCE: The activation of P2X7 receptors by ATP induces apoptosis and autophagy in human epithelial cells, possibly via ROS production, and this effect might have implications for gut inflammatory conditions.

Evidence for a perforin-mediated mechanism controlling cardiac inflammation in Trypanosoma cruzi infection.

CD8+ T lymphocytes are considered an important cell population involved in the control of parasitaemia and mortality after Trypanosoma cruzi infection. However, despite recent developments in this field, the mechanism whereby this control is exerted is still not completely understood. Here we have used perforin knockout (-/-) mice infected with Y strain T. cruzi in order to evaluate specifically the participation of the perforin-based cytotoxic pathway in the destruction of cardiomyocytes, cellular inflammatory infiltration, and control of parasitaemia and mortality. We observed that although parasitaemia was equivalent in perforin (+/+) and (-/-) groups, survival rate and spontaneous physical performance were significantly lower in the perforin deficient mice. The cardiac inflammatory cell infiltration, mostly composed of CD8+ cells, was more evident in perforin (-/-) mice. Ultrastructural and immunofluorescence analysis, as well as plasma creatine kinase activity, revealed cardiomyocyte damage and necrosis, more evident in perforin (-/-) mice. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assays performed in heart samples revealed similar and modest levels of apoptosis in both perforin (+/+) and (-/-) mice. These results indicate that perforin does not play a pivotal role in the control of parasitaemia and direct lysis of cardiomyocytes, but seems to be an important molecule involved in the control of cardiac inflammation and pathology induced by a highly virulent strain of T. cruzi.