Effect of several laser systems on removal of smear layer with a variety of irrigation solutions.

To evaluate which laser system is more effective on smear layer removal when distilled water or combination of sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) are used as irrigants. Ninety-six human mandibular premolar teeth were used. Standard access cavities were prepared and the root canals were enlarged using ProTaper system to size F4 and divided into two equal groups according to final irrigation solution. In Group 1, distilled water was used, whilst 2.5% NaOCI and 17% EDTA solutions were used in Group 2. Each group was divided into four equal subgroups according to the activation procedure. In Subgroups 1A (Control) and 2A, no activation protocol was applied. In other subgroups, Er:YAG laser using photon-induced photoacoustic streaming (PIPS; 1B and 2B), Nd:YAG laser (1C and 2C) and Er,Cr:YSGG laser (1D and 2D) were applied for the activation. Teeth were split longitudinally and subjected to scanning electron microscopy evaluation. Smear layer was scored at 1000× magnification in all thirds. The data were analysed statistically using Kruskal-Wallis and Mann-Whitney U test post hoc comparisons. The samples irrigated with distilled water had greater smear layer scores when compared with the combination of NaOCl and EDTA (p < .05). The efficacy of smear layer removal increased when using laser systems (p < .05). Smear layer was removed more effectively in the coronal and middle levels compared to the apical level (p < .05). The sequential use of NaOCl and EDTA is significantly more effective than distilled water in smear layer removal. Regardless of the type of irrigant, laser activated irrigation enhances smear layer removal. RESEARCH HIGHLIGHTS: The use of laser systems for activation of NaOCl and EDTA is the most effective method in terms of smear layer removal. Photon-induced photoacoustic streaming technique with Er:YAG laser was the most efficient smear layer removal method regardless of the solution used.