RESUMO
Aim: To evaluate the influence of ultrasonic activation (US) with different irrigant regimens in smearlayer removal. Methods: One hundred bovine incisors were instrumented and divided into tengroups (n=10) according to final irrigation protocols: distilled water (DW); DW+US; 17% EDTA;QMix; 10% citric acid; 37% phosphoric acid; 17% EDTA+US; QMix+US; 10% citric acid+US; 37%phosphoric acid+US. The samples were then submitted to scanning electron microscopy where ascore system was used to evaluate the images and effectiveness of proposed treatments. The datawere statistically analyzed by Kruskal-Wallis and Mann-Whitney U tests for intergroup comparisonsas well as the Wilcoxon and Friedman tests for intragroup comparisons at 5% significance level.Results: In the cervical third, groups 17% EDTA, QMix, 10% citric acid, 17% EDTA+US, QMix+USand 10% citric acid+US were more effective in smear layer removal (p<0.05); in the middle third,groups 17% EDTA+US and QMix+US were more effective in smear layer removal (p<0.05); in theapical third, groups 17% EDTA,17% EDTA+US and QMix+US were more effective in smear layerremoval (p<0.05). Conclusions: US can aid 17% EDTA and QMix in smear layer removal at themiddle third and QMix at the apical third, contributing to the cleaning of root canal system.