Abstract
The aim of this study was to evaluate the effectiveness of smear layer removal after the use of different irrigation methods (passive ultrasonic irrigation (PUI), continuous ultrasonic irrigation (CUI), apical negative pressure irrigation and conventional irrigation) using scanning electron microscopy (SEM) as an analytical tool. A total of 100 single-canal teeth were decoronated and randomly divided into five groups (n = 20) according to the irrigation method used: conventional irrigation with front outlet syringe, conventional irrigation with lateral outlet syringe, apical negative pressure irrigation (EndoVac), PUI with Irrisafe and CUI with ProUltra PiezoFlow ultrasonic irrigation needle. Root canal preparation was performed with the ProTaper Gold system up to the F4 instrument, and 5.25% NaOCl was used as an irrigant. After chemical-mechanical preparation, the roots were split longitudinally, and the coronal, middle and apical thirds were examined. SEM digital photomicrographs were taken at ×1000 magnification to evaluate the amount of smear layer in each root canal third; CUI significantly removed more smear layer than any other irrigant activation protocol (p < 0.05); CUI was more effective in removing the smear layer than the other irrigation protocols. However, none of the irrigation protocols were able to produce root canals completely free from smear layer.
Highlights
Smear layer can be defined as an irregular layer of organic and inorganic components, formed on the dentinal walls during root canal instrumentation [1]
Significant differences among the root thirds were observed in all experimental groups (p < 0.05), with the middle third showing a more pronounced removal of smear layer (Table 1), meaning that complete removal of smear layer with any system was higher in the middle third than the other two
continuous ultrasonic irrigation (CUI) and passive ultrasonic irrigation (PUI) significantly removed more smear layer than the other groups in both middle and apical thirds (p < 0.05), while, in apical negative pressure (ANP) and CISV groups, none of the samples showed a complete absence of smear layer in the apical third
Summary
Smear layer can be defined as an irregular layer of organic and inorganic components, formed on the dentinal walls during root canal instrumentation [1]. Its association with a chelating agent, such as ethylenediaminetetraacetic acid (EDTA), is more than necessary to provide an effective removal of this layer from the root canal walls [4,5,6,7]. Conventional irrigation with syringe has been the most used technique to irrigate root canals, the replenishment and exchange of the irrigant are limited in the apical part of this system [11]. In this sense, several irrigant techniques have been proposed to overcome this limitation
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