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Introduction: Complete endodontic system disinfection requires the removal of vital and necrotic pulp tissue, microorganisms, and toxins. The purpose of this study was to compare the effects of 2 ultrasonic irrigation techniques on the penetration of sodium hypochlorite into the main canal and simulated lateral canals of extracted teeth., Methods: Two simulated lateral canals each were created 2, 4, and 6 mm from the working length in 60 single-rooted teeth (6 canals/tooth, n = 360). To resemble the clinical situation, a closed system was created in each tooth. The teeth were randomly assigned to 3 experimental irrigation groups: group 1 (n = 20), positive pressure irrigation (PPI); group 2 (n = 20), passive ultrasonic irrigation (PUI); and group 3 (n = 20), continuous ultrasonic irrigation (CUI). Samples were evaluated by direct observation of still images recorded under a dental operating microscope. To examine irrigating solution penetration, 20% Chinese ink (Sanford Rotring GmbH, Hamburg, Germany) was added to a 5% sodium hypochlorite solution and delivered into the root canals., Results: The results showed a significantly higher (P < .05) penetration of irrigant into the lateral canals in the CUI group. PUI and CUI did not differ significantly in solution penetration into the apical thirds of the main canals. The PPI group showed a significantly lower penetration of sodium hypochlorite into the main and lateral canals compared with the CUI and PUI groups., Conclusions: CUI as a final rinse significantly increased the penetration of irrigating solution into simulated lateral canals., (Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: This in vitro study compared the tooth color and the ultrastructure of internal dental tissues before and after internal bleaching., Methods: Sodium perborate was placed in the pulp chamber of endodontically treated molars and sealed with intermediate restorative material. The test samples were stored in a physiologic solution, and the bleaching agent was replaced every 7 days. A control group was used. After 1 month, the colors of the test and control samples were measured with a colorimeter, and the internal surfaces were observed under field emission scanning electron microscopy (FESEM)., Results: Statistically significant differences were found between the test and control sample colors. The FESEM ultrastructure analysis of the internal enamel and dentin surfaces did not show any changes after the internal bleaching., Conclusions: The results of the present study show that sodium perborate is effective in bleaching nonvital teeth and does not produce ultrastructural changes in the dental tissues., (Copyright 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Objective: The aim of this study was to compare the scanning electron microscopic (SEM) morphology of root canal walls instrumented manually and mechanically with and without the application of Er:YAG laser., Methods: Single-rooted, human, extracted teeth were cut at the cementoenamel junction. The teeth were divided into four groups: teeth that were simply instrumented manually, those that were instrumented manually and laser treated, a group that was mechanically instrumented, and a fourth in which the teeth were mechanically instrumented and laser treated. After instrumentation, the teeth were split longitudinally to facilitate their evaluation by SEM., Results: The results show that the use of the Er:YAG laser is effective in removing the smear layer from root canal walls., Conclusions: The removal of the smear layer is essential to the success of endodontic treatment; the use of the Er:YAG laser combined with rotary and manual techniques improves the cleanliness of root canals.