Related Experiment Video
Updated: Jun 20, 2025
Scanning Electron Microscopic Evaluation of Surface Defects of Remover Retreatment File After Single and Multiple Uses
Published on: October 11, 2024
Smear layer removal efficacy of different irrigation techniques in conservatively instrumented root canals
Sota Mochizuki1, Satoshi Watanabe1, Jiayi Liu1
1Department of Pulp Biology and Endodontics, Division of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.
Background/Purpose:
Establishing effective irrigation methods is warranted to ensure the predictability of minimally invasive root canal instrumentation. This study aimed to compare the smear layer removal efficacy of different irrigation techniques in root canals instrumented with TruNatomy nickel-titanium rotary instruments.
Materials And Methods:
Experiment 1: Extracted human mandibular incisors were instrumented using TruNatomy Shaping Files up to Small (#20/0.04), Prime (#26/0.04), or Medium (#36/0.03) (n = 17, each) and irrigated with EDTA, NaOCl, and again with EDTA using syringe irrigation (SI). Experiment 2: Extracted mandibular incisors were instrumented using TruNatomy Small and irrigated with EDTA and NaOCl as in Experiment 1, using (1) conventional laser-activated irrigation (LAI) with an erbium-doped yttrium aluminum garnet laser unit at 30 mJ/10 Hz (LAI 30/10) or 70 mJ/20 Hz (LAI 70/20), (2) photon-induced photoacoustic streaming (PIPS) (20 mJ/15 Hz), (3) ultrasonic-activated irrigation, or (4) SI (n = 13 each). Five additional canals served as negative controls (no irrigation). The smear layer on the canal wall was scored under scanning electron microscopy.
Results:
In Experiment 1, the TruNatomy Small group exhibited significantly higher smear layer scores compared to the other groups in the apical and middle thirds. In Experiment 2, the LAI 70/20 and PIPS groups demonstrated significantly lower smear layer scores compared to the LAI 30/10 and SI groups in the apical third.
Conclusion:
Conservative instrumentation using the TruNatomy Small reduced the cleaning efficacy of irrigation. However, PIPS performed satisfactory for smear layer removal without injury to the root canal wall.
