Methods: sixty human single-root teeth were selected. After instrumentation the root canals were inoculated with E. Faecalis and randomly divided into six groups (n=10). Four groups received a solution of 0.01% methylene blue for 5 min followed by irradiation using a diode laser at a wavelength of 680 nm, than according to the employed parameters they were divided in: G1- irradiated with 216 micron intracanal optical fiber, at a power output (P) of 90mW and irradiation time (t) of 1min 30s;G2- irradiated with 600 micron hand peace placed on the root canal orifice (without intracanal optical fiber), P=100mW and t=1min 30s, G3- irradiated with intracanal optical fiber, P= 90mW and t=3min; G4- irradiated as the same way as the group G2 (without optical fiber), P= 100mW and t=3min. The two other groups served as control: G5 (positive control)- treated with 1% sodium hypochlorite solution for 15min and G6 (negative control)- did not undergo any intervention. Bacterial samples were taken before and after irradiation. In each of the samples, the number of colony-forming units (CFU) was counted.
Results: all treatments resulted in reduction of microrganisms and the mean decrease in CFU was: G1- 99,48%, G2-99,41%, G3-99,65 %, G4-99,64% and G5-100%, with no significant difference between the irradiated groups (p>0.05).
Conclusions: the photodynamic effectiveness with the irradiated parameters employed in this study was independent of the use of intracanal optical fiber.