Objective: This study examined the bactericidal effect of diode laser irradiation against intracanal Enterococcus faecalis.
Methods and materials: m total of 128 extracted single-rooted and single-canal teeth were treated with ProTaper instruments (Dentsply Maillefer, Ballaigues, Switzerland). A total of 120 root canals were inoculated with E. faecalis for 21 days, and the samples were randomly divided into five groups: Group 1 (n = 24) samples were irrigated with only saline solution (positive controls); Group 2 (n = 24) was treated with only 5.25% sodium hypochlorite; Group 3 (n = 24) was irrigated with saline solutions activated by diode laser; Group 4 (n = 24) was treated with 5.25% sodium hypochlorite activated by diode laser; and Group 5 (n = 24) was irrigated with saline solution with methylene blue dye activated by the diode laser Fox (Sweden & Martina, Padova, Italy); additionally, eight teeth were not contaminated and their canals were irrigated with saline solution and used as a negative control. The Uro-Quick system was used to determine the microbial residual charge. The data were analyzed using Pearson's chi-square test (p < 0.001).
Results: A statistically significant reduction in bacterial count was observed in Group 2 and Group 4 (p < 0.001). There were no statistically significant differences among the other groups (p > 0.001).
Conclusions: Evidence indicates that the diode laser was not more effective than sodium hypochlorite in reducing free bacteria.
Keywords: diode laser; endodontics; lasers in dentistry.