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.

Erbium-doped yttrium aluminum garnet (Er:YAG) laser-activated irrigation (LAI) is used in endodontic treatment to remove the smear layer and kill bacteria in the root canal. However, this procedure can cause photo-thermal effects that harm the surrounding tissue. Therefore, it was important to study the temperature changes that occur at the outer tooth surface during activation of the Er:YAG laser using a side-firing spiral Endo tip in the root canal. Laser treatment was performed either in the absence of fluid in the root canal or in the presence of a 17% EDTA solution. Irrigation with 17% EDTA was either performed in a continuous mode for 60 s or in a segmented mode of 4 rinses with 17% EDTA for 15 s each. The temperature was measured every second during the treatment at three tooth surface sites: the cementoenamel junction, the middle region and the apical region. Our data show that the greatest temperature changes occurred when the laser was used alone without an irrigation solution, while minor temperature changes were observed with continuous irrigation. In conclusion, we would recommend applying the laser treatment with an irrigation solution to avoid excessive heating.