Efficacy of root canal disinfection using Er:YAG laser

Methods: 120 freshly extracted, human, single-rooted teeth were divided into four groups. In group 1 complete root canal treatment (# 60) was performed, whereas only initial shaping (# 40) was carried out in groups 2 to 4 to achieve equal root canal volumes. All teeth were sterilized (ethylene oxide), inoculated with Enterococcus faecalis, and incubated for three days. The number of CFU was counted after plating and incubation on blood agar. Subsequently, complete root canal treatment was performed in groups 2 to 4 using sterile NaCl solution (0.9%) in group 2, NaOCl (1%) in group 3, and CHX (0.2%) in group 4 (10 ml each). Finally, in half of the teeth (n = 15) of each group Ca(OH)₂ was applied for three days; alternatively, the Er:YAG laser was used to disinfect root canals of the other 15 teeth per group. Evaluation of CFU after treatment was done following incubation time of two days (by adding sterile culture medium).

Results: In groups 1 and 2 the median reduction of CFU after application of Ca(OH)₂ was significantly higher (factor 10⁴ each) than after Er:YAG laser-treatment (factor 10² each, Mann-Whitney test). The efficacy of disinfection was significantly increased by using NaOCl as well as CHX as irrigating solutions; in most of the specimens of groups 3 and 4 no bacteria were detectable anymore.

Conclusion: The Er:YAG laser does not seem to be suitable for sufficient disinfection of Enterococcus faecalis containing root canals, whereas Ca(OH)₂ was, in contrast to several published studies, highly efficacious. NaOCl and CHX increase the efficacy of disinfection.