Er:YAG 2,940-nm laser fiber in endodontic treatment: a help in removing smear layer

Cleaning and disinfection of the root canal system are some of the most important goals in endodontic therapy. The aim of this preliminary study is to assess the effectiveness of Er:YAG laser fiber in removing the smear layer produced during root canal walls instrumentation. Forty-eight single-rooted teeth were prepared with manual and rotary Ni-Ti instruments, in addition to 2.5 % NaOCl irrigation. Samples were randomly subdivided into groups and treated with: three irradiations of 5 s each, with 300-mu m Er:YAG endodontic fiber, 1 W and 2.5 % NaOCl solution (A Group); two laser irradiations with 17 % EDTA solution and 2.5 % NaOCl solution (B Group); laser irradiation plus 17 % EDTA solution and 2.5 % NaOCl (C Group); only in the final wash of 17 % EDTA (control group D). During laser treatment, temperature variations were analyzed by using thermocouple and thermal camera devices in order to test both deep and superficial temperatures. Each sample was finally observed by scanning electron microscope (SEM) at the coronal, medium, and apical thirds at x500 magnification and blindly scored depending on the amount of smear layer. Statistical analysis of the results was conducted using the Kruskal-Wallis and Mann-Whitney test to determine the eventual significant differences between the quantity of smear layer in each group and between the groups at coronal, medium, and apical third: a p value < 0.05 was considered significant. The thermal analysis realized by thermocouple with the used parameters demonstrated that laser endodontic fiber produces an average deep temperature increase of 3.5 +/- 0.4 A degrees C; analysis performed with a thermal camera showed an average superficial temperature increase of 1.3 A +/- 0.2 A degrees C produced by laser endodontic fiber use. Deep and superficial temperatures fall immediately after irradiation possibly without causing structural damage or anatomical alteration inside the root canal and neither on periodontal tissues. SEM analysis showed that specimens of group B had the highest level of cleaning in every third, with a significant difference with groups D and A; group C samples showed a good percentage of cleaned tubules in apical and middle thirds, while group D teeth showed open dentinal tubules in coronal third, with a statistical difference with group A samples which were the worst cleaned. The Er:YAG fiber double irradiation with EDTA 17 % and NaOCl 2.5 % has been demonstrated to be effective in removing smear layer, even in the apical third which is described as the hardest area to clean during endodontic treatment.