Introduction: to compare the effect of Er,Cr:YSGG-laser-activated and conventional irrigation techniques on intracanal smear layer elimination at the apical, middle, and coronal segments of root canal walls using environmental scanning electron microscope (ESEM). Methods: Thirty-six freshly extracted human single-rooted single-canal anterior teeth were selected for this study. The root canals were conventionally accessed, then prepared by using ProTaper Next® system to size X4, 0.06 taper and divided into two equal groups (n = 18); syringe/needle- and laser-activated groups. Each group was further subdivided into three subgroups; saline, NaOCl, and salvadora P (6 teeth each). Er,Cr:YSGG-laser was emitted at pulse energy of 25 mJ, pulse width of 60 μs, pulse frequency of 50 Hz and delivered by a radial firing tip. Teeth were longitudinally sectioned for ESEM assessment. Data were collected and statistically analyzed by Kruskal-Wallis and Mann-Whitney tests. Results: Er,Cr:YSGG-laser-activated generally showed better smear layer removal results than syringe/needle activated group. The statistical significant differences occurred between NaOCl and salvadora P subgroups at coronal and middle, and apical thirds, respectively. Salvadora P presented higher statistical smear layer removingcapacity than the other comparative subgroups at coronal third when Er:Cr:YSSG-laser-activated technique was used and at coronal and middle thirds when the conventional technique was applied. Conclusion: Er,Cr:YSGG-laser-activated irrigation technique had a positive effect on removing of smear layer. Laser-activated Salvadora P was effectively removed smear layer from the entire root dentin while the conventionally-activated salvadora P was more potent at coronal and middle thirds. Clinical significance: Er,Cr:YSGG-laser can effectively activate the intracanal irrigants

Er, Cr:YSGG laser, RFT, smear layer removal, root canal irrigation