RESUMO
Laser irradiation has been introduced in endodontic treatment due to its bactericidal effect. The aim of this study is to evaluate the bactericidal efficacy of a 940 nm diode laser alone or in combination with 5% sodium hypochlorite [NaOCl] against mature biofilms of E. Faecalis. Sixty-eight [60 for the three groups, 4 for SEM and 4 as negative controls] single-rooted human central incisors were prepared and contaminated with E. Faecalis. After two weeks of incubation, specimens were randomly divided in three groups; group 1 [n =20], the teeth were irradiated with a 940 nm diode laser; group 2 [n=20], specimens were rinsed with 5% NaOCl; group 3 [n=20], the teeth were rinsed with 5% NaOCl and then were irradiated with 940 nm diode laser. Four teeth were used to observe the biofilms by SEM. Intracanal bacteria sampling was done, and the samples were plated to determinate the CFU count. At 24 hours and 7 days, group 3 showed a significant difference [P=0,02; P=0,00] in disinfection if compared to group 1 but did not show this difference if compared to group 2 [P=1, P=0,66], although group 3 obtaining a more extensive disinfection. Groups 1 and 2 did not show difference after 24 hours [P=0,09] but showed a significant difference 7 days afterwards [P=0,04]. The combination of sodium hypochlorite and diode laser light [940 nm] has a synergistic effect, intensifying the bactericidal action.