Nd:YAG laser irradiation in root canal disinfection.

The purpose of this study was to assess the efficacy of Nd:YAG laser irradiation in disinfecting the root canal system. Seventy-five teeth were uniformly instrumented and sterilized, and their root canals were infected for 60 min with an overnight culture of Enterococcus faecalis in Tryptic Soy Broth. The teeth were divided into 6 groups: 1--non-infected controls; 2--infected controls; 3--infected, laser treated; 4--infected, laser dummy (dye only); 5--infected, laser dummy (dye and air-water spray); 6--infected, NaOCl-treated (reference group). After treatment, the root canals were dried and dentinal shavings removed for a post-treatment culture. Quantitative analysis of bacteria surviving the various treatments were performed and the bacterial counts for each group were compared. SEM analysis of teeth split longitudinally was used to illustrate the effect of treatment on the smear layer and on surface bacteria. Nd:YAG laser irradiation (group 3) significantly reduced the number of bacteria while NaOCl irrigation (group 6) effectively disinfected the canals.