Objective: This study aimed to evaluate the effectiveness of photon-induced photoacoustic streaming (PIPS), XP-endo Finisher (XPF), and passive ultrasonic irrigation (PUI) for the removal of root canal filling materials from oval root canals. Background: Various adjunctive irrigation techniques following mechanical preparation have been applied to enhance removal of fillings during root canal retreatment. However, whether there is superiority of one approach over others remains controversial. Methods: Thirty extracted single-rooted teeth with oval-shaped canals were instrumented with the ProTaper Next (PTN) system and obturated with the warm vertical compaction technique. After storage at 37°C for 1 month, retreatment was performed with the PTN system up to size X4. The teeth were then randomly assigned into three groups (n = 10) that were, respectively, subjected to supplementary irrigation with different protocols: PIPS, PUI, and XPF, followed by measurement of filling material volumes using high-resolution micro-computed tomography. Results: The PTN preparation resulted in significant reductions in residual filling materials (p < 0.05), whereas PIPS, PUI, and XPF moderately improved the removal of the remnants (p > 0.05). The residual filling materials after supplementary irrigation ranged from 0.384 ± 0.181 to 0.421 ± 0.143 mm3 in oval canals. There was no significant difference in the effectiveness among the PIPS, PUI, and XPF approaches (p > 0.05). Conclusions: Mechanical preparations are useful for removing most root fillings during retreatment in oval-shaped canals. PIPS can reduce residual root-filling materials to the similar extent as PUI and XPF.
Keywords: XP-endo Finisher; endodontic retreatment; laser; micro-CT; passive ultrasonic irrigation; photon-induced photoacoustic streaming.