Hard tissue debris removal from the mesial root canal system of mandibular molars with ultrasonically and laser-activated irrigation: a micro-computed tomography study

This study is to investigate the efficacy of different irrigant activation techniques on removal of accumulated hard tissue debris (AHTD) in mesial roots of human mandibular molars. Extracted human mandibular molars with an isthmus between the mesial root canals were selected based on micro-CT (μCT) scans. The mesial canals were instrumented to an apical diameter ISO30 using ProTaper rotary files. Teeth were randomly assigned to three irrigant activation groups (n = 10): ultrasonically activated irrigation (UAI) using a size 20 Irrisafe for 3 × 20 s, laser-activated irrigation (LAI) with an Er:YAG laser (2940 nm) and plain 300 μm fiber tip inside the canal (20 mJ, 20 Hz, 3 × 20 s), and laser-activated irrigation with identical parameters with a 400 μm photon-induced photoacoustic streaming (PIPS) tip held at the canal entrance. All teeth were scanned with μCT before and after instrumentation and after irrigant activation. After reconstruction and image processing, the canal system volume filled with hard tissue debris before and after irrigant activation was calculated. Changes in hard tissue debris volumes were compared between groups using one-way ANOVA. The percentage volume of hard tissue debris (vol%) was significantly lower after irrigant activation in all groups. Although the lowest debris values were observed in the laser groups, no significant differences in the vol% of accumulated hard tissue debris after activation were observed between groups. Accumulated hard tissue debris was reduced significantly in all activation groups. Ultrasonically and laser-activated irrigation regimens performed similarly in this respect. None of the tested methods was able to render the root canal systems free of debris.