Antibacterial Effect of Er:YAG Laser Irradiation Applied by a New Side-Firing Spiral Tip on <i>Enterococcus faecalis</i> Biofilm in the Tooth Root Canal—An <i>Ex Vivo</i> Study

This study evaluates the antibacterial and anti-biofilm effect of erbium:yttrium aluminum garnet (Er:YAG) laser treatment on a tooth root model infected with Enterococcus faecalis. Background: New treatment options are required to overcome endodontic infection in periapical tissue. Studies using Er:YAG during endodontic treatment yielded promising results regarding anti-biofilm/antimicrobial effects. Methods: The root canals of 80 teeth were incubated with E. faecalis for 4 weeks, allowing biofilm formation in the root canals, then divided into one control group and seven treatment groups that were exposed to Er:YAG laser using a side-firing spiral Endo tip, 2.5% sodium hypochlorite (NaOCl), 17% EDTA solutions alone or combined. The number of bacteria in each sample was determined by counting the number of colony-forming units (CFU) and was statistically compared. Results: Er:YAG laser, NaOCl and EDTA treatments alone caused a 76.0 ± 5.7%, 98.0 ± 0.6% and 69.0 ± 9.1% reduction, respectively, in CFU. Combining the laser treatment with NaOCl, EDTA or both, caused a further reduction in the bacterial load by 99.77 ± 0.14%, 93.4 ± 1.6% and 99.95 ± 0.04%, respectively. Conclusions: Er:YAG laser treatment showed significant antibacterial effect on the experimental groups, while combination with NaOCl and EDTA provided the most efficient conditions for achieving antibacterial effect against E. faecalis, in the tooth root model