 This study compared the antibacterial efficacy of cold atmospheric plasma, CAP, photodynamic therapy, PDT, with two photosensitizers, PSS, and diode laser for disinfection of primary mandibular second molar root canals infected with enterococcus fecalis, E, fecalis. The results showed that CAP was most effective at eliminating E, fecalis, followed by PDT and diode laser. Additionally, CAP was found to be more effective than PDT and diode laser as an adjunct to mechanical root canal disinfection of primary molars for elimination of E, fecalis, and can serve as an alternative to 2.5% sodium hypochloride irrigation. This article was authored by Leili Haafi, Arosh Azizi, Mehdi Vattemper, and others.