Comparative analysis of laser and ultrasonic irrigation techniques for smear layer removal in endodontics

Abstract

Objective: This in vitro study compared the efficacy of Er, Cr: YSGG laser (2780 nm), diode laser (976 nm), passive ultrasonic irrigation (PUI), and conventional syringe-needle (CSN) irrigation in smear layer removal, evaluating irrigant chemistry and root canal level. Methods: 160 single-rooted premolars were instrumented and divided into four irrigation groups (n = 40/group): Er, Cr: YSGG (25 mJ, 50 Hz, radial-firing tip), diode laser (Pulsed 50%, 1.5 W), PUI, and CSN (side-vented needle). Groups were subdivided by irrigant (NaOCl + EDTA, EDTA, NaOCl, saline; n = 10/subgroup). Activation involved four 15-second cycles. Smear layer was scored (1–5) via SEM by blinded evaluators. Data were analyzed with Kruskal-Wallis and Mann-Whitney tests (p ≤ 0.05). Results: Er, Cr: YSGG achieved the lowest scores (best cleaning) across all thirds, outperforming diode laser, PUI, and CSN. NaOCl + EDTA was the most effective irrigant (p < 0.05). Remarkably, saline with Er, Cr: YSGG surpassed NaOCl alone. Apical thirds showed consistently poorer removal. Conclusion: Er, Cr: YSGG laser activation with NaOCl + EDTA is the most effective protocol for smear layer removal. The powerful mechanical effects of Er, Cr: YSGG dominated when using saline. Diode laser activation also surpassed PUI.