Bactericidal Effect of Nd:YAG and Er:YAG Lasers in Experimentally Infected Curved Root Canals

Objective: The purpose of this study was to evaluate the bactericidal efficacy of Nd:YAG and Er:YAG laser in the experimentally infected curved root canals. Background Data: Previous studies revealed that laser systems have a significant bactericidal effect in both human and bovine infected straight root canals. Materials and Methods: Sixty extracted single-rooted teeth with single root canals were selected and then instrumented with endodontic files to a size 60 (K-type file). The degree of root curvature was determined according to modified Schneider's method. Each of the specimens was incubated in a sterile centrifuge tube with 1 mL of the Enterococcus faecalis suspension at 37 degrees C for 2 weeks under aerobic conditions. After laser irradiation at each of the two settings, 50 mJ, 10 pps (0.5W) or 100 mJ, 10 pps (1.0 W), the number of E. faecalis in each root canal was examined. Results: In the straight root canals, the Er: YAG laser showed higher bactericidal effects by 6.4-10.8% than did the Nd: YAG laser. Conversely, the bactericidal effect of Er: YAG laser in the curved root canals was higher by 1.5-3.1% than was that with the Nd: YAG laser. The bactericidal effect of the Er: YAG laser in the curved root canal is significantly lower than that in the straight root canal (p < 0.05). Conclusion: These results suggest that further development in the endodontic laser tip and technique is required to ensure its success in curved root canals sterilization.