Removal of the smear layer by passive and continuous ultrasonic irrigation: a scanning electron microscopy study.
Background: Due to the anatomical complexity of the root canal system, irrigation plays an essential role in endodontics. This in vitro study was sought to compare the removal of the smear layer (RSL) promoted by conventional irrigation (CI), passive ultrasonic irrigation (PUI) and continuous ultrasonic irrigation (CUI) with 17% EDTA, by using scanning electron microscopy (SEM). Material and Methods: Forty single-rooted human mandibular canines were instrumented and randomly assigned to four groups (n=10), according to the irrigation protocol aiming to the RSL: CG (control group) —conventional irrigation with distilled water; CI— conventional irrigation with 17% EDTA; PUI —passive ultrasonic irrigation with 17% EDTA; CUI— continuous ultrasonic irrigation with 17% EDTA. Hemisections from each sample were obtained, and images of each root canal third (cervical, middle and apical) were captured at 1000 X magnification by SEM. Three previously calibrated and blinded evaluators classified the RSL, according to the criteria proposed by Torabinejad et al.: small or no smear layer (all dentinal tubules were clean and open); 2 = moderate smear layer (no smear layer on the surface of root canal, but dentinal tubules contained debris); 3 = dense smear layer (covering practically all dentinal tubules entrances). Statistical analysis was performed by Kruskal-Wallis and Bonferroni tests (p<0.05). Results: Overall, CUI and cervical thirds showed better RSL rates, compared with the other methods and thirds, respectively (p<0.05). More specifically, the cervical thirds showed better results in the CG, CI and PUI groups (p<0.05), whereas the cervical and middle thirds were not significantly different in the CUI group. Conclusion: CUI was the most effective method for the RSL.
. Haapasalo M, Shen Y, Wang Z, Gao Y. Irrigation in endodontics. Brit Dent J. 2014;216(6):299-303.
. Violich DR, Chandler NP. The smear layer in endodontics - a review. Int Endod J. 2010;43(1):2-15.
. Shahravan A, Haghdoost AA, Adl A, Rahimi H, Shadifar F. Effect of smear layer on sealing ability of canal obturation: a systematic review and meta-analysis. J Endod. 2007;33(2):96-105.
. Mozo S, Llena C, Forner L. Review of ultrasonic irrigation in endodontics: increasing action of irrigating solutions. Med Oral Patol Oral Cir Bucal. 2012;17(3):e512-6.
. Weller RN, Brady JM, Bernier WE. Efficacy of ultrasonic cleaning. J Endod. 1980;6(9):740-3.
. Jamleh A, Suda H, Adorno CG. Irrigation effectiveness of continuous ultrasonic irrigation system: An ex vivo study. Den Mat J. 2018;37(1):1-5.
. Schneider SW. A comparison of canal preparations in straight and curved root canals. Oral Surg Oral Med Oral Pathol. 1971;32(2):271-5.
. Bueno CRE, Cury MTS, Vasques AMV, Sarmiento JL, Trizzi JQ, Jacinto RC, Sivieri-Araujo G, Dezan Júnior E. Cleaning effectiveness of a nickel-titanium ultrasonic tip in ultrasonically activated irrigation: a SEM study. Braz Oral Res. 2019;33:e017. doi: 10.1590/1807-3107bor-2019.vol33.0017. PMID: 30892412.
. Mancini M, Cerroni L, Iorio L, Armellin E, Conte G, Cianconi L. Removal of the smear layer and canal cleanliness using different irrigation systems (EndoActivator, EndoVac, and passive ultrasonic irrigation): field emission scanning electron microscopic evaluation in an in vitro study. J Endod. 2013;39(11):1456-60.
. Silva EJNL, Carvalho CR, Belladonna FG, Prado MC, Lopes RT, De-Deus G, Moreira EJL. Micro-CT evaluation of different final irrigation protocols on the removal of hard-tissue debris from isthmus-containing mesial root of mandibular molars. Clin Oral Investig. 2019;23(2):681-7.
. Schmidt TF, Teixeira CS, Felippe MC, Felippe WT, Pashley DH, Bortoluzzi EA. Effect of Ultrasonic Activation of Irrigants on Removal of the smear layer. J Endod. 2015;41(8):1359-63.
. Torabinejad M, Khademi AA, Babagoli J, et al. A new solution for the removal of the smear layer. J Endod. 2003;29(3):170-5.
. Mader CL, Baumgartner JC, Peters DD. Scanning electron microscopic investigation of the smeared layer on root canal walls. J Endod. 1984;10(10):477-83.
. Peeters HH, Suardita K. Efficacy of removal of the smear layer at the root tip by using ethylenediaminetetraacetic acid and erbium, chromium: yttrium, scandium, gallium garnet laser. J Endod. 2011;37(11):1585-9.
. Salzgeber RM, Brilliant JD. An in vivo evaluation of the penetration of an irrigating solution in root canals. J Endod. 1977;3(10):394-8.
. Machado R, Garcia L, da Silva Neto UX, Cruz Filho AMD, Silva RG, Vansan LP. Evaluation of 17% EDTA and 10% citric acid in removal of the smear layer and tubular dentin sealer penetration. Microsc Res Tech. 2018;81(3):275-82.
. Herrera DR, Martinho FC, de-Jesus-Soares A, et al. Clinical efficacy of EDTA ultrasonic activation in the reduction of endotoxins and cultivable bacteria. Int Endod J. 2017;50(10):933-40.
. Rodrigues RCV, Zandi H, Kristoffersen AK, et al. Influence of the Apical Preparation Size and the Irrigant Type on Bacterial Reduction in Root Canal-treated Teeth with Apical Periodontitis. J Endod. 2017;43(7):1058-63.
. Matos FS, Khoury RD, Carvalho CAT, Martinho FC, Bresciani E, Valera MC. Effect of EDTA and QMIX Ultrasonic Activation on the Reduction of Microorganisms and Endotoxins in Ex Vivo Human Root Canals. Braz Dent J. 2019;30(3):220-6.
. Darcey J, Jawad S, Taylor C, Roudsari RV, Hunter M. Modern Endodontic Principles Part 4: Irrigation. Dent Update. 2016;43(1):20-33.
. Marques AC, Aguiar BA, Frota LM, Guimarães BM, Vivacqua-Gomes N, Vivan RR, Duarte MA, de Vasconcelos BC. Evaluation of Influence of Widening Apical Preparation of Root Canals on Efficiency of Ethylenediaminetetraacetic Acid Agitation Protocols: Study by Scanning Electron Microscopy. J Contemp Dent Pract. 2018 ;19(9):1087-94.
. Agarwal A, Deore RB, Rudagi K, Nanda Z, Baig MO, Fareez MA. Evaluation of Apical Vapor Lock Formation and comparative Evaluation of its Elimination using Three different Techniques: An in vitro Study. J Contemp Dent Pract. 2017;18(9):790-4.
. Chan R, Versiani MA, Friedman S, Malkhassian G, Sousa-Neto MD, Leoni GB, Silva-Sousa YTC, Basrani B. Efficacy of 3 Supplementary Irrigation Protocols in the Removal of Hard Tissue Debris from the Mesial Root Canal System of Mandibular Molars. J Endod. 2019;45(7):923-9.
. Moorer WR, Wesselink PR. Factors promoting the tissue dissolving capability of sodium hypochlorite. Int Endod J. 1982;15(4):187-96.
. da Costa Lima GA, Aguiar CM, Camara AC, Alves LC, Dos Santos FA, do Nascimento AE. Comparison of smear layer removal using the Nd:YAG laser, ultrasound, ProTaper Universal system, and CanalBrush methods: an in vitro study. J Endod. 2015;41(3):400-4.
. Walmsley AD. Ultrasound and root canal treatment: the need for scientific evaluation. Int Endod J. 1987;20(3):105-11.
. Jiang LM, Lak B, Eijsvogels LM, Wesselink P, van der Sluis LW. Comparison of the cleaning efficacy of different final irrigation techniques. J Endod. 2012;38(6):838-41.
. Jiang LM, Verhaagen B, Versluis M, van der Sluis LW. Evaluation of a sonic device designed to activate irrigant in the root canal. J Endod. 2010;36(1):143-6.
. De-Deus G, Reis C, Paciornik S. Critical appraisal of published smear layer-removal studies: methodological issues. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2011;112(4):531-43.
. Machado R, Comparin D, Back E, Garcia L, Alberton LR. Residual smear layer after root canal instrumentation by using Niti, M-Wire and CM-Wire instruments: A scanning electron microscopy analysis. Eur J Dent. 2018;12(3):403-9.
. Layton G, Wu WI, Selvaganapathy PR, Friedman S, Kishen A. Fluid Dynamics and Biofilm Removal Generated by Syringe-delivered and 2 Ultrasonic-assisted Irrigation Methods: A Novel Experimental Approach. J Endod. 2015;41(6):884-9.
. Huang TY, Gulabivala K, Ng YL. A bio-molecular film ex-vivo model to evaluate the influence of canal dimensions and irrigation variables on the efficacy of irrigation. Int Endod J. 2008;41(1):60-71.
. McGill S, Gulabivala K, Mordan N, Ng YL. The efficacy of dynamic irrigation using a commercially available system (RinsEndo) determined by removal of a collagen 'bio-molecular film' from an ex vivo model. Int Endod J. 2008;41(7):602-8.
. Nogo-Zivanovic D, Kanjevac T, Bjelovic L, Ristic V, Tanaskovic I. The effect of final irrigation with MTAD, QMix, and EDTA on removal of the smear layer and mineral content of root canal dentin. Microsc Res Tech. 2019;82(6):923-30.
. Matos FS, da Silva FR, Paranhos LR, Moura CCG, Bresciani E, Valera MC. The effect of 17% EDTA and QMiX ultrasonic activation on smear layer removal and sealer penetration: ex vivo study. Sci Rep. 2020;10:10311.
. Carrigan PJ, Morse DR, Furst ML, Sinai IH. A scanning electron microscopic evaluation of human dentinal tubules according to age and location. J Endod. 1984;10(8):359-63.
. Iriboz E, Bayraktar K, Turkaydin D, Tarcin B. Comparison of apical extrusion of sodium hypochlorite using 4 different root canal irrigation techniques. J Endod. 2015;41(3):380-4.
. Fukumoto Y, Kikuchi I, Yoshioka T, Kobayashi C, Suda H. An ex vivo evaluation of a new root canal irrigation technique with intracanal aspiration. Int Endod J. 2006;39(2):93-9.
. Mitchell RP, Yang SE, Baumgartner JC. Comparison of apical extrusion of NaOCl using the EndoVac or needle irrigation of root canals. J Endod. 2010;36(2):338-41.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. © 2023.