Efficacy of passive ultrasonic irrigation in removing residual root filling material during retreatment: ex vivo analyses by micro-CT and confocal laser scanning microscope

Aim: To evaluate the volume of residual filling material after desobturation and passive ultrasonic irrigation (PUI) with irrigants and an organic solvent using micro-computed tomography (micro-CT), and assess the penetrability of the obturation of retreatment using confocal laser scanning microscope (CLSM).

Methodology: Thirty curved mesial roots of mandibular molars were submitted for endodontic treatment. After, the filling material was removed and the root canals were reinstrumented with ProTaper instruments (Stage 1). The specimens were randomly assigned according to the protocol of supplementary cleaning (Stage 2). In the Manual group, orange oil solvent, 2.5% NaOCl, and 17% EDTA were applied in the root canal with syringe and needle. In the PUI group, the same irrigants were submitted to ultrasonic agitation. The volume of residual filling material was measured by micro-CT. After, the specimens were filled and submitted to CLSM. The micro-CT data were analyzed by Mann-Whitney and Friedman tests at 5%. The Wilcoxon and Mann-Whitney tests were used for CLSM data (P<.05).

Results: Both supplementary cleaning protocols decreased the amount of residual filling material, when compared with stage 1 (P<.05). The PUI group showed significantly less percentages of residual filling material than did the Manual group, for all of the thirds of the root canal (P<.05). There were no statistically significant difference in the penetrability of the obturation of retreatment in the recessions areas between the Manual and PUI groups (P>.05).

Conclusions: The use of the PUI as a supplementary technique in removing residual filling material after desobturation was more effective than manual agitation.