Adjuvant therapy with a 980-nm diode laser in root canal retreatment: randomized clinical trial with 1-year follow-up

The purpose of this study is to assess the laser effect in root canal disinfection and periapical healing of endodontically treated teeth from patients with asymptomatic apical periodontitis. This study was performed as a randomized clinical trial. Thirty patients were selected according to the inclusion/exclusion criteria. Fifteen patients received the root canal retreatment (RCR) combined with 980-nm diode laser irradiation (LI). The canals were irrigated with saline solution and gently dried with paper points, keeping the dentin partially moist. The irradiation was performed using a 320-µm-diameter fiber in helicoidal movements (pulsed mode, power output of 1.5 W, 100 Hz for 20 s). The other 15 patients received the RCR with placebo irradiation (PI). Microbiological samples were taken in three periods: S1, after the filling material removal (baseline); S2, after laser or placebo irradiation (LI or PI); and S3, after the RCR followed by laser or placebo. The samples were submitted to the total microbial and E. faecalis counting. The periapical radiographic healing was analyzed after 3, 6, 9, and 12 months. Microbiological data (CFU/mg) were analyzed by ANOVA and Tukey’s test ( P