Comparative Evaluation of Calcium Hypochlorite and Sodium Hypochlorite Associated with Passive Ultrasonic Irrigation on Antimicrobial Activity of a Root Canal System Infected with Enterococcus faecalis: An In Vitro Study

Abstract Introduction The purpose of this study was to compare in vitro the effectiveness of calcium hypochlorite (Ca[OCl] 2 ) and sodium hypochlorite (NaOCl) associated with passive ultrasonic irrigation in root canals of bovine teeth infected with Enterococcus faecalis . Methods The root canals of 60 single-rooted bovine extracted teeth were enlarged up to a file 45, autoclaved, inoculated with Enterococcus faecalis , and incubated for 30 days. The samples were divided into 6 groups ( n  = 10) according to the protocol for decontamination: G1: no treatment; G2: distilled water; G3: 2.5% NaOCl; G4: 2.5% Ca(OCl) 2 ; G5: 2.5% NaOCl with ultrasonic activation; and G6: 2.5% Ca(OCl) 2 with ultrasonic activation (US). Microbiological testing (colony-forming unit [CFU] counting) was performed to evaluate and show, respectively, the effectiveness of the proposed treatments. Data were subjected to 1-way analysis of variance followed by the post hoc Tukey test (α = 0.05). Results Groups 1 and 2 showed the highest mean contamination (3.26 log 10  CFU/mL and 2.69 log 10  CFU/mL, respectively), which was statistically different from all other groups ( P 2  + US) showed the lowest mean contamination (1.00 log 10  CFU/mL), with no statistically significant difference found in groups 3 (NaOCl), 4 (Ca[OCl] 2 ), and 5 (NaOCl + US) ( P Conclusions Ca(OCl) 2 as well as passive ultrasonic irrigation can aid in chemomechanical preparation, contributing in a significant way to the reduction of microbial content during root canal treatment.