Antibiofilm Activity of Sodium Hypochlorite and Alkaline Tetrasodium EDTA Solutions

The aim of this study was to determine the antimicrobial activity of mixed alkaline tetrasodium EDTA (EDTANa₄)/sodium hypochlorite (NaOCl) solutions with and without the addition of cetrimide (CTR) against Enterococcus faecalis biofilms.

The antimicrobial solutions were evaluated on a 3-week biofilm of E. faecalis grown on radicular dentin blocks. The irrigating solutions were 2.5% NaOCl group, 20% EDTANa₄ group, 10% EDTANa₄ group, 2.5% NaOCl/10% EDTANa₄ group, 2.5% NaOCl/5% EDTANa₄ group, 2.5% NaOCl/10% EDTANa₄/0.2% CTR group, 2.5% NaOCl/5% EDTANa₄/0.2% CTR group, and 0.9% saline solution group. Cell viability was determined by adenosine triphosphate assay, and culture techniques were used to determine colony-forming unit (CFU) counts. In groups with positive growth, the Pearson linear correlation coefficient r (-1 ≤ r ≤ 1) between relative light units (RLUs) and log₁₀ (CFUs + 1) was calculated. The results of the bioluminescence adenosine triphosphate assay and CFUs of the groups were analyzed by means of analysis of variance and the Duncan test.

There was Pearson correlation between RLUs and log₁₀ (CFUs + 1). A similar reduction of RLUs in all NaOCl groups was seen, giving statistical differences with respect to the control. In the NaOCl groups there was no bacterial growth. The lowest antimicrobial efficacy was found for the EDTANa₄ groups.

Mixed alkaline EDTANa₄/NaOCl solutions with and without the addition of CTR do not interfere with the antimicrobial activity of NaOCl.