Histological evaluation of root canal cleaning by different final irrigation protocols

Aim: This study aimed to evaluate in vitro the ability to remove pulp tissue from the mesial root canals of mandibular molars using three different protocols for the final activation time of irrigation with the Easy Clean (EC) rotary instrument. Materials and Methods: Thirty mandibular molars with vital pulp were instrumented with the ProDesign Logic rotary system and divided into three experimental groups according to the protocol for the final activation time of the irrigants (n=10). Group EC1: the final rinse was performed with 5 mL of 2.5% sodium hypochlorite (NaOCl), followed by 5 mL of 17% ethylenediaminetetraacetic acid (EDTA) and another 5 mL of 2.5% NaOCl solution, with each rinsing agent activated in 3 cycles of 20 seconds. Group EC2 used the same sequence of solutions as group EC1, with each irrigant activated in 6 cycles of 20 seconds. In group EC3, the operation technique and the sequence of solutions were the same as in groups EC1 and EC2, with each rinsing agent being activated in 9 cycles of 20 seconds. At the end, samples from all groups were washed with 20 mL of distilled water using a NavigTip 30-G syringe and needle. The samples were fixed in 10% formaldehyde, cut into micrometers, fixed on histology slides and stained with hematoxylin-eosin (HE). The total area of the canal and remaining tissue was determined using the Image J program to determine the percentage of remaining pulp. Results: In the cervical third, all groups had similar results. In the middle and apical thirds, EC1 and EC2 had similar percentages of pulp remnants and differed from EC3 (p<0.05). Conclusions: It can be concluded that the removal of pulp tissue increases with longer contact time of the NaOCl.