Micro-CT study on the removal of accumulated hard-tissue debris from the root canal system of mandibular molars when using a novel laser-activated irrigation approach.

Abstract

To compare the efficacy of ultrasonically activated irrigation (UAI), photon-induced photoacoustic streaming (PIPS) and shock wave enhanced emission photoacoustic streaming (SWEEPS) activation for the removal of accumulated hard-tissue debris (AHTD) from the root canal system of mandibular molars when assessed using microcomputed tomography (micro-CT). A total of 30 mandibular first and second molars with joining mesial root canals containing an isthmus and a single distal canal were subjected to three micro-CT scans (before and after canal instrumentation and after final irrigation) at a resolution of 15μm. Mesial canals were prepared up to aProTaper F3 rotary file, and distal canals were prepared up to aProTaper F4 rotary file. Teeth were randomly assigned to three groups according to the irrigant activation method (n=10): the UAI group, the PIPS group and the SWEEPS group. The final irrigation procedures were performed using a total of 15.5mL of 1% NaOCl for each tooth with an activation time of 3×30s. After three-dimensional model reconstruction and volumetric measurement of root canals, the percentage reduction (%Rd) of AHTD was calculated. The %Rd of AHTD was analysed statistically using one-way analysis of variance and nonparametric tests at a significance level of 5%. There were no significant differences between the three groups in terms of canal volume before or after instrumentation, or the volume of debris after canal preparation (P>0.05). In the mesial canals, irrigation with SWEEPS reduced the overall debris by 84.31%, which was significantly more than the reduction associated with PIPS and UAI (58.79% and 50.27%, respectively). In the distal canals, the %Rd of AHTD was significantly different between PIPS and SWEEPS and between UAI and SWEEPS (P<0.05), but was not significantly different between PIPS and UAI groups (P>0.05). The SWEEPS was associated with a greater %Rd of AHTD than the PIPS and UAI groups. SWEEPS was associated with significantly less debris compared than PIPS and UAI, especially in isthmus-containing mesial roots. None of the activation techniques completely removed debris from root canal systems.