The bactericidal effect of Nd:YAG, Ho:YAG, and Er:YAG laser irradiation in the root canal: an in vitro comparison. 
The aim of this study was to compare the antibacterial effectiveness of the Nd:YAG, the Ho:YAG, and the Er:YAG laser in infected root canals.  Lasers are gaining increasing importance in the field of endodontics.  Numerous studies have shown the beneficial effects of laser treatment in disinfecting root canals.  In our in vitro experimental setup, 40 extracted and endodontically treated teeth were inoculated with a suspension of Escherichia coli and Enterococcus faecalis and then irradiated at standardized power settings.  The disinfecting efficacy of each laser was proved by classical microbiological examination.  This article highlights that all three lasers substantially decreased the bacterial population with only minimal differences in their microbicidal efficacy.  At 1.5 W, the best results were obtained by the Er:YAG laser achieving a mean bacterial elimination of 99.64%, followed by the Nd:YAG laser (99.16%), and the Ho:YAG laser (99.05%).  Our findings indicate that all three lasers act as strongly effective microbicides without causing unfavorable temperature rises at the settings used.  They can thus be considered a valuable tool for root canal treatment.