Laser Activated Photoacoustic Streaming in Retreatment of Curved Root Canals
Objectives: This pilot study evaluated the efficacy of passive ultrasonic irrigation (PUI) and Er:YAG laser activated irrigation modes: photon-induced photoacoustic streaming (PIPS) and schock wave enhanced emission photoaacoustic streaming (SWEEPS) in the removal of filling remnants after conventional retreatment in severely curved root canals.
Methods: Mesiobuccal curved root canals of 32 extracted mandibular/maxillar molars were instrumented with ProTaper Next system up to size 25, .06 and filled with epoxy resin-based sealer and gutta-percha using continuous wave vertical compaction and warm injection back-filling. The samples were retreated using ProTaper Universal Retreatment system and sodium hypochlorite (NaOCl) and, then, randomly divided into four groups (n=8) according to the final irrigation technique: PUI; PIPS; SWEEPS with flat-tip; SWEEPS with conical-tip. A total of 6 mL of 3% NaOCl was used for each canal with an activation time of 3x30 s. The samples were subjected to three micro-CT scans: after root canal filling, after root canal retreatment and after final irrigation. The volume of the filling material and the percentage reduction were calculated. The decrease in the amount of filling material after each retreatment phase was analysed using Kruskal–Wallis test. Intergroup differences were analysed using Mann–Whitney U test (p<0.05).
Results: The results of the study showed that all tested irrigation techniques reduced significantly the remaining filling material after the retreatment (p<0.05). SWEEPS with flat-tip showed significantly less efficacy in removing the filling remnants compared to the SWEEPS with conical tip (p=0.046) and PUI (p=0.021). There were no significant difference between PUI, SWEEPS with conical-tip and PIPS (p>0.05). Also, no siginificant difference was observed between PIPS and SWEEPS with flat-tip (p=0.093).
Conclusions: All tested techniques improved the removal of filling material during retreatment in curved canals. SWEEPS with conical-tip, PIPS and PUI were equally effective.