Antimicrobial activity of different irrigation solutions on Enterococcus faecalis in the root canal of the primary teeth—an in vitro comparative study

Background: Enterococcus faecalis is a key pathogen in persistent endodontic infections, particularly in primary teeth with complex root canal anatomy. This study aimed to compare the antimicrobial efficacy of five irrigation solutions against E. faecalis. Methods: Seventy-five extracted primary teeth were prepared and inoculated with E. faecalis (3 × 109 CFU/mL) then divided into five groups (n = 15): 2.5% sodium hypochlorite (NaOCl), 5% ethylenediaminetetraacetic acid (EDTA), 9% etidronic acid, 17% glycolic acid, and 0.9% physiological saline (NaCl). Root canals were irrigated, and bacterial samples were collected at 30 minutes, 24 hours, and 72 hours. Bacterial counts were analyzed using ANOVA (p < 0.05). Results: NaOCl, etidronic acid, and glycolic acid significantly reduced E. faecalis counts within 30 minutes. EDTA showed no immediate effect but inhibited bacterial growth by 24 hours. NaCl caused a gradual reduction in bacterial load over time (p = 0.02). Conclusions: Etidronic and glycolic acids were effective alternatives to NaOCl in disinfecting primary tooth root canals. These agents may offer biocompatible options in pediatric endodontics, but further in vivo studies are warranted.