Chitosan: a new solution for removal of smear layer after root canal instrumentation P. V. Silva 1 , D. F. C. Guedes 1 , F. V. Nakadi 2 , J. D. Pe ´ cora 1 & A. M. Cruz-Filho 1 1 Department of Restorative Dentistry, Ribeira ˜o Preto School of Dentistry, University of Sa ˜o Paulo; and 2 Ribeira ˜o Preto Chemistry School, University of Sa ˜o Paulo, Ribeira ˜o Preto, Sa ˜o Paulo, Brazil Abstract Silva PV, Guedes DFC, Nakadi FV, Pe ´ cora JD, Cruz-Filho AM. Chitosan: a new solution for removal of smear layer after root canal instrumentation. International Endodontic Journal. Aim To evaluate, by scanning electron microscopy (SEM), the efficacy of smear layer removal using chitosan compared with different chelating agents, and to quantify, by atomic absorption spectrophotom- etry with flame (AASF), the concentration of calcium ions in these solutions after irrigation. Methodology The root canals of twenty-five canines were prepared using a crown-down technique and irrigated with 1% sodium hypochlorite. The teeth were randomly divided into groups (n = 5), according to the type of final irrigation: 15% EDTA, 0.2% chito- san, 10% citric acid, 1% acetic acid and control (with- out final irrigation). The total volume of each chelating solution was collected from the canals and analysed by AASF for quantification of calcium ions in the solutions. Then, the roots were split longitudi- nally and examined by SEM for evaluation of smear layer removal in the middle and apical thirds. Clean- ing scores were attributed and analysed statistically using the Kruskal–Wallis and Dunn tests. The AASF data were analysed by one-way ANOVA and Tukey– Kramer test. A significant level of a = 0.05 was adopted. Results 15% EDTA, 0.2% chitosan and 10% citric acid had similar smear layer removal capacity with a significant difference (P < 0.05) from 1% acetic acid and the control group. There was no significant differ- ence (P > 0.05) between the smear layer remaining in the middle and apical thirds. The highest calcium ion concentration was observed with 15% EDTA (121.80 ± 5.13) and 0.2% chitosan (104.13 ± 19.23), with no significant difference. The lowest cal- cium ion concentration was obtained with 1% acetic acid (25.62 ± 7.68), whilst 10% citric acid (70.38 ± 11.15) had intermediate results, differing significantly from the other solutions (P < 0.01). Conclusions 15% EDTA, 0.2% chitosan and 10% citric acid effectively removed smear layer from the middle and apical thirds of the root canal. 15% EDTA and 0.2% chitosan were associated with the greatest effect on root dentine demineralization, followed by 10% citric acid and 1% acetic acid. Keywords: chelating agents, chitosan, EDTA, irrigation, smear layer. Received 27 February 2012; accepted 22 July 2012 Introduction Ethylenediaminetetraacetic acid (EDTA) is the most widely used irrigant for smear layer removal (Marques et al. 2006, Estrela et al. 2007, Spano ´ et al. 2009) and complements the cleaning of root canals by acting on inorganic material. Its reaction with cal- cium ions in dentine results in calcium chelation, pro- moting decalcification of dentine at approximate depths of 20–30 lm within 5 min (von der Fehr & Nygaard-O ¨ stby 1963). The search for more biocompatible solutions than EDTA, aiming at minimizing its harmful effect on periapical tissues continues. Environmental concerns Correspondence: Antonio M. Cruz-Filho, Departamento de Odontologia Restauradora, Faculdade de Odontologia de Ribeira ˜o Preto, USP, Avenida do Cafe ´, S/ N, CEP: 14040- 904, Ribeira ˜o Preto, SP, Brasil (Tel: +55-16-3602-4792; Fax: +55-16-3633-0999; e-mail: cruz@forp.usp.br). © 2012 International Endodontic Journal International Endodontic Journal doi:10.1111/j.1365-2591.2012.02119.x 1