RESUMO
Aim: This study evaluated both smear layer removal and reduction of Enterococcus faecalis after instrumentation with ultrasonic irrigation. Methods: Root canals were experimentally inoculated with E. faecalis for 20 days and microbiological samples were collected before and after chemomechanical preparation by using sterilized absorbent paper points. The irrigation solutions used were NaOCl 2.5% and EDTA 17%. In Group 1 (G1), conventional irrigation was used, whereas in Group 2 (G2) ultrasonic irrigation was performed. In group 3 (control), root canals were irrigated with distilled water. The samples were inoculated in BHI broth and turbidity was observed after 48 h to evaluate the reduction in the number of bacteria. Residual smear layer was examined by scanning electron microscopy (SEM). Results: The results showed no significant differences between ultrasonic and conventional irrigation. Conclusions: It was concluded that the level of disinfection and cleanliness of root canals achieved with ultrasonic irrigation is comparable to that obtained by conventional methods.