Assessment of smear layer removal protocols in curved root canals

This study sought to assess if the final rinse protocol interferes with the smear layer removal in the apical area of curved canals. Sixty-four extracted human mandibular molars with curved mesial roots were instrumented with rotary files and divided into six experimental groups for final rinse: 1EDTA (syringe irrigation with 1mL of 17% ethylenediaminetetraacetic acid (EDTA)), 5EDTA (syringe irrigation with 5mL of 17% EDTA), 1EDTA-P (syringe irrigation with 1mL of 17% EDTA+pumping with gutta-percha point), 5EDTA-P (syringe irrigation with 5mL of 17% EDTA+pumping with gutta-percha point), 1EDTA-EA (syringe irrigation with 1mL of 17% EDTA+EndoActivator) and 5EDTA-EA (syringe irrigation with 5mL of 17% EDTA+EndoActivator). Final rinsing was carried out over 3min. The specimens were split lengthwise and observed under a scanning electron microscope using a score criterion. Comparison among the groups showed statistically significant difference only between the 5EDTA-EA group and the other groups (Kruskal-Wallis and Dunn's post-hoc tests, P<0.05). The combination of 5mL of 17% EDTA and 3mL of 2.5% sodium hypochlorite (NaOCl) with the EndoActivator removed smear layer from the apical area of curved root canals more effectively than the other protocols used.