RESUMO
INTRODUCTION: The aim of this blind, in vivo, randomized controlled trial was to evaluate the antibacterial effect of Nd:YAG laser irradiation in endodontic treatment of single-rooted teeth with apical periodontitis. The hypothesis was that mechanical enlargement of the root canal and Nd:YAG laser irradiation would yield more negative bacterial samples than conventional treatment. METHODS: Forty-one patients (45 teeth) were allocated to the laser (n = 22) or control (n = 23) group. The teeth in the laser group were instrumented, irrigated with saline, and irradiated with Nd:YAG laser according to a standard protocol. The teeth in the control group were similarly instrumented but irrigated with 1% unbuffered sodium hypochlorite and 15% EDTA solution. Bacterial samples were taken before and after treatment, blinded, and immediately sent for culturing and analysis. RESULTS: The initial bacterial samples were positive in 20 of 22 teeth in the laser group and 18 of 23 (P = .414) in the control group. After the initial treatment, negative bacterial samples were found in 11 teeth in the laser group and 13 (P = .768) in the control group. After 2 to 4 days with no antibacterial dressing in the root canals, 5 teeth in the laser group and 9 (P = .337) in the control group yielded negative bacterial samples. CONCLUSIONS: After intervention, neither the test group nor the control group yielded predictable negative bacterial samples. Thus, the results failed to verify the hypothesis that Nd:YAG laser irradiation would yield significantly more negative bacterial samples than conventional irrigation with 1% unbuffered sodium hypochlorite solution.