Prolonged sodium hypochlorite exposure on root canal disinfection: an in vitro study

Abstract

Objective: This study evaluated whether prolonged sodium hypochlorite exposure improves antibacterial efficacy in infected root canals. Material and method: 44 human mandibular premolars were contaminated with Enterococcus faecalis and randomly assigned to four groups according to the irrigation protocol: saline, saline with prolonged exposure, 2.5% sodium hypochlorite, and sodium hypochlorite with prolonged exposure. Microbiological samples were collected after chemomechanical preparation, after the prolonged exposure phase, and after passive ultrasonic irrigation. Bacterial reduction was quantified by colony-forming unit (CFU) counts. Scanning electron microscopy was used for qualitative analysis. Data were analyzed using two-way analysis of variance and the Bonferroni test (α = 0.05). Result: Chemomechanical preparation with sodium hypochlorite significantly reduced bacterial counts compared with saline (p < 0.05). The addition of prolonged exposure did not result in further bacterial reduction (p > 0.05). Passive ultrasonic irrigation produced an additional reduction in bacterial counts in the sodium hypochlorite groups (p < 0.05). Scanning electron microscopy analysis showed decreased microbial presence in all groups, although residual microorganisms were observed. Conclusion: Prolonging sodium hypochlorite contact time through a prolonged exposure protocol did not enhance antibacterial efficacy compared with conventional irrigation. Irrigation strategies that include sodium hypochlorite during chemomechanical preparation combined with irrigant activation appear sufficient to achieve significant bacterial reduction.