RESUMO
INTRODUCTION: Instrumentation of the mesial root canal system of mandibular molars may hinder disinfection by packing hard tissue debris within the isthmuses. The removal of accumulated hard tissue debris (AHTD) by 3 supplemental irrigation systems, 2 ultrasonically activated and 1 multisonic, was assessed with micro-computed tomographic imaging. METHODS: Twenty-four extracted mandibular molars with 2 mesial canals connected by an isthmus and converging to a single foramen were selected. After preparation of the mesial canals with WaveOne Gold instruments (Dentsply Maillefer, Ballaigues, Switzerland), anatomically matched specimens were assigned to 3 final irrigation protocols (n = 8): intermittent ultrasonic (IU) with an ultrasonically energized 200-µm wire (Irrisafe; Satelec, Bordeaux, France), continuous ultrasonic (CU) with an ultrasonic irrigation needle (ProUltra PiezoFlow, Dentsply Maillefer), and GentleWave (GW) system (Sonendo Inc, Laguna Hills, CA). Specimens were scanned (SkyScan 1176; Bruker-microCT, Kontich, Belgium) at 17.18-µm pixel size before and after preparation and irrigation protocols. Data sets were coregistered, and the percentage reduction of AHTD calculated within the canals and isthmus for each specimen was statistically compared using 1-way analysis of variance and post hoc Tukey tests with a 5% significance level. RESULTS: The mean percentage reduction of AHTD in canals and isthmuses was significantly higher for GW (96.4% and 97.9%, respectively) than for CU (80.0% and 88.9%, respectively) (P < .05). AHTD reduction for IU (91.2% and 93.5%, respectively) did not differ significantly from GW and CU (P > .05). CONCLUSIONS: GW achieved greater efficacy in the removal of AHTD from the mesial root canal system of mandibular molars compared with CU but not IU. The efficacy of CU and IU was comparable.