The Impact of Three Different Canal Lubricants on Fracture, Deformity and Metal Slivering of ProTaper Rotary Instruments

Introduction: The aim of this in vitro study was to evaluate the effect(s) of three canal lubricants i.e. sodium hypochlorite, RC-Prep as the paste form of ethylenediaminetetraacetic acid (EDTA) and aqueous EDTA, on the occurrence/incidence of fracture, deformity and metal slivering of ProTaper rotary instruments. Methods: A total of 120 mesial canals (i.e. mesiobuccal and mesiolingual) of first mandibular molars or buccal canals (i.e. mesiobuccal and distobuccal) of first maxillary molars, with curvatures of 10-20 degrees were selected and randomly divided into three groups of forty samples each. These selected canals all had approximate 19-21 mm working length and apical diameter equal to a #15 K-file. In each group, the root canals were prepared using ProTaper rotary instruments with an electric motor using one of the three aforementioned irrigants. Subsequently, samples were compared to each other at different magnifications (16×, 20×, 40× and 57×) for any fracture, deformity or metal slivering, by the Cox regression analysis. Results: The fractures rate of samples in RC-Prep group was significantly higher compared to other groups (P=0.01). No evidence of instrument deformity was detected in any groups. A statistically significant reverse relation between metal slivering and instrument fracture was observed. Conclusions: Application of aqueous EDTA and/or sodium hypochlorite as intracanal lubricants caused less fracture of ProTaper instruments compared to canal lubrication with RC-Prep

Phospholipid Composition Modulates Carbon Nanodiamond-Induced Alterations in Phospholipid Domain Formation

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Langmuir, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://doi.org/10.1021/la504923j.The focus of this work is to elucidate how phospholipid composition can modulate lipid nanoparticle interactions in phospholipid monolayer systems. We report on alterations in lipid domain formation induced by anionically engineered carbon nanodiamonds (ECNs) as a function of lipid headgroup charge and alkyl chain saturation. Using surface pressure vs area isotherms, monolayer compressibility, and fluorescence microscopy, we found that anionic ECNs induced domain shape alterations in zwitterionic phosphatidylcholine lipids, irrespective of the lipid alkyl chain saturation, even when the surface pressure vs area isotherms did not show any significant changes. Bean-shaped structures characteristic of dipalmitoylphosphatidylcholine (DPPC) were converted to multilobed, fractal, or spiral domains as a result of exposure to ECNs, indicating that ECNs lower the line tension between domains in the case of zwitterionic lipids. For membrane systems containing anionic phospholipids, ECN-induced changes in domain packing were related to the electrostatic interactions between the anionic ECNs and the anionic lipid headgroups, even when zwitterionic lipids are present in excess. By comparing the measured size distributions with our recently developed theory derived by minimizing the free energy associated with the domain energy and mixing entropy, we found that the change in line tension induced by anionic ECNs is dominated by the charge in the condensed lipid domains. Atomic force microscopy images of the transferred anionic films confirm that the location of the anionic ECNs in the lipid monolayers is also modulated by the charge on the condensed lipid domains. Because biological membranes such as lung surfactants contain both saturated and unsaturated phospholipids with different lipid headgroup charges, our results suggest that when studying potential adverse effects of nanoparticles on biological systems the role of lipid compositions cannot be neglected

Assessment of Root Morphology and Apices of First and Second Maxillary Molars in Tehran Population

Introduction: Objective: This study aimed to assess the possible variations in root canal anatomy and topography of the apices of first and second maxillary molars. Materials and methods: A total of 67 first and second maxillary permanent molars were collected. Access cavity was prepared and 2% methylene blue was injected. The teeth were demineralized by 5% nitric acid and cleared with methyl salicylate. Specimens were evaluated under stereomicroscopy and analyzed using the sample t-test. Results: Based on Vertucci’s classification, the mesiobuccal root of maxillary first molars was type I in 87.5% and type IV in 12.5% of the cases. The mesiobuccal root of second maxillary molars was type I in 60%, type II in 8.6%, type IV in 25.7% and type V in 5.7% of cases. In maxillary first and second molars, the distobuccal and palatal roots were type I in 100% of the cases. The distance of the apical constriction from the apical foramen was 0.21±0.09 mm, the distance from the apical constriction tothe anatomic apex was 0.44±0.19 mm and the distance of the apical foramen from the anatomic apex was 0.15±0.15 mm. The mean percentage of delta prevalence was 3.2% in both teeth. Conclusion: The mean distance of the apical foramen and apical constriction from the anatomic apex was less than 0.6 and 1.2 mm, respectively. In maxillary first and second molars, the mean distance of the apical constriction from the apical foramen and anatomic apex was 0.21 and 0.44, respectively and the mean distance of the apical foramen from the anatomic apex was 0.15 m