Hydrogen Sulfide Sensitizes Acinetobacter baumannii to Killing by Antibiotics.

The production of endogenous hydrogen sulfide (H2S) has been shown to confer antibiotic tolerance in all bacteria studied to date. Therefore, this mediator has been speculated to be a universal defense mechanism against antibiotics in bacteria. This is assuming that all bacteria produce endogenous H2S. In this study, we established that the pathogenic bacteria Acinetobacter baumannii does not produce endogenous H2S, giving us the opportunity to test the effect of exogenous H2S on antibiotic tolerance in a bacterium that does not produce it. By using a H2S-releasing compound to modulate the sulfide content in A. baumannii, we demonstrated that instead of conferring antibiotic tolerance, exogenous H2S sensitized A. baumannii to multiple antibiotic classes, and was able to revert acquired resistance to gentamicin. Exogenous H2S triggered a perturbation of redox and energy homeostasis that translated into hypersensitivity to antibiotic killing. We propose that H2S could be used as an antibiotic-potentiator and resistance-reversion agent in bacteria that do not produce it.

Role of pH Changes on Transforming Growth Factor-ß1 Release and on the Fibrin Architecture of Platelet-rich Fibrin When Layered with Biodentine, Glass Ionomer Cement, and Intermediate Restorative Material.

INTRODUCTION: The purpose of this study was to evaluate the influence of pH that is due to setting reaction of Biodentine, glass ionomer cement (GIC), and intermediate restorative material (IRM) on transforming growth factor-ß1 (TGF-ß1) release and on the fibrin architecture of platelet-rich fibrin (PRF). METHODS: PRF was obtained from 8 volunteers and layered over the freshly prepared GIC, IRM, and Biodentine mixtures. TGF-ß1 release was estimated by using enzyme-linked immunosorbent assay (ELISA), and fibrin structure of PRF was analyzed by using scanning electron microscope at 1 and 5 hours. RESULTS: Biodentine, GIC, and IRM increased the TGF-ß1 release in comparison with that of control group (PRF alone) at both 1 and 5 hours. Biodentine released significantly more TGF-ß1 than GIC and IRM at 1 hour. At 5 hours both GIC and Biodentine released significantly more TGF-ß1 than IRM. The fibrin architecture of the Biodentine group was similar to that of control group at both 1 and 5 hours. In GIC and IRM groups the fibrillar structure of fibrin was collapsed, ill-defined, and cloudy with very thick fibers and irregularly reduced porosities. CONCLUSIONS: Biodentine induces larger amount of TGF-ß1 release and also maintains the integrity of fibrin structure when compared with GIC and IRM when layered over PRF.

Endodontic management of a maxillary first molar with eight root canal systems evaluated using cone-beam computed tomography scanning: a case report.

INTRODUCTION: Root canal treatment of maxillary molars presenting with complex root canal configurations can be diagnostically and technically challenging. METHODS: Nonsurgical endodontic therapy of a left maxillary first molar with three roots and eight root canals was successfully performed. This unusual morphology was diagnosed using a dental operating microscope (DOM) and confirmed with the help of cone-beam computed tomography (CBCT) images. RESULTS: CBCT axial images showed that both the mesiobuccal and distobuccal root contained a Sert and Bayirli type XV canal, whereas the palatal root showed a Vertucci type II canal configuration. CONCLUSIONS: The use of a DOM and CBCT imaging in endodontically challenging cases can facilitate a better understanding of the complex root canal anatomy, which ultimately enables the clinician to explore the root canal system and clean, shape, and obturate it more efficiently.