Laser applications in smear layer removal from posterior root canals: A comparative study

AIM: The aim of the study is to evaluate erbium laser efficiency in removing smear layer from mesial roots of mandibular first molars at different laser settings. SUBJECTS AND METHODS: One hundred (100) mandibular first molars were selected. Ninety six (96) mesial roots were assigned to two experimental groups according to the laser wavelength applied: I. Er, Cr: YSGG and II. erbium-doped yttrium aluminum garnet laser system. Four samples were used as control group. Samples of each group were distributed into two subgroups (A and B), following specific irrigation protocol. Each subgroup was divided into four subcategories according to the applied power laser. Each subcategory consisted of six samples. Teeth were observed under scanning electron microscope. STATISTICAL ANALYSIS: Results were statistically analyzed with Kruskal–Wallis and Mann–Whitney test (SPSS statistics software). RESULTS: No statistically significant difference was observed between experimental groups I and ΙΙ. However, statistically significant difference was found among subgroups IA and ΙB and ΙIA and ΙΙΒ. In every root third, groups IIA and ΙΙB had better outcomes but it was not statistically significant. There was no statistically significant difference among subcategories of Group I (ΙΑ(1-4) and ΙΒ(1-4)) and Group ΙΙ (ΙΙΑ(1-4) and ΙΙΒ(1-4)). CONCLUSION: Erbium laser with tested parameters did not completely remove the smear layer from the root canals. Chelating factors can contribute in the laser mechanism of smear layer removal from apical part of narrow and curved root canals.