Comparisons of the smear layer removal efficacy of dual-action irrigants and different activation techniques

Dual-action root canal irrigants containing disinfectant(s) and chelator(s) are expected to enhance root canal cleaning efficiency. This study aimed to evaluate the effectiveness of these irrigants and different activation techniques on smear layer removal. Seventy-six extracted human mandibular premolars were root canal-prepared up to an apical size of #40/0.06, grouped and irrigated as follows, and the smear layer on each third of the canal wall was evaluated using scanning electron microscopy. In Experiment 1, syringe irrigation (SI) was carried out using a dual-action irrigant (Triton or SmearOFF) or a combination of 17% ethylenediaminetetraacetic acid (EDTA) and 6% sodium hypochlorite (NaOCl) (n = 12, each). In Experiment 2, Triton was activated by laser-activated irrigation (LAI) with a novel Er:YAG laser equipment (Adverl SH, Morita Manufacturing, Kyoto, Japan), an LAI protocol called shockwave-enhanced emission photoacoustic streaming (SWEEPS), or ultrasonic-activated irrigation (UAI), and irrigated with SI (n = 10, each). In Experiment 1, the Triton group demonstrated significantly better smear layer scores than the EDTA and NaOCl combination group across all canal thirds (P < 0.05). In Experiment 2, using Triton as the irrigant, the LAI and SWEEPS groups exhibited significantly superior smear layer scores compared to the UAI group across all canal thirds (P < 0.05). Triton was more effective than the combination of EDTA and NaOCl in removing the smear layer across all root canal thirds. The efficacy of Triton was further enhanced by activation with LAI and SWEEPS.