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Publisher: Peytchinski Publishing Ltd.
ISSN: 1312-773X (Online)
Issue: 2026, vol. 32, issue4
Subject Area: Dental Medicine
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DOI: 10.5272/jimab.2026324.7160
Published online: 15 October 2026
Original article
J of IMAB. 2026 Oct-Dec;32(4):7160-7164
ANTIMICROBIAL EFFICACY OF SODIUM HYPOCHLORITE ALONE AND COMBINED WITH DUAL RINSE HEDP AGAINST ENTEROCOCCUS FAECALIS: AN IN VITRO STUDY
Aleksandra Pecheva1
, Kostadin Georgiev1, Emiliya Simeonova1, Elena Boyadzhieva1, Iliyan Dobrev2,
1) Department of Operative dentistry and endodontics, Faculty of Dental Medicine, Medical University of Plovdiv, Bulgaria.
2) Department of Microbiology and Biotechnologies, Faculty of Technology, University of Food Technologies, Plovdiv, Bulgaria.
ABSTRACT:
Purpose: This in vitro study evaluated the antimicrobial effectiveness of 5.25% sodium hypochlorite (NaOCl) alone and combined with the commercially available Dual Rinse HEDP (Medcem, Switzerland), which contains etidronic acid (1-hydroxyethylidene-1,1-diphosphonic acid, HEDP) in powder form, against Enterococcus faecalis.
Materials and methods: The study involved preparing bacterial cultures of Enterococcus faecalis, which were grown on esculin base agar and Luria-Bertani (LB) agar, then suspended in sterile saline to a concentration of approximately 8×108 CFU/ml. These cultures were spread in Petri dishes, followed by punching wells, adding test solutions (Group I – 5.25% NaOCl; Group II – Dual Rinse HEDP dissolved in 5.25% NaOCl; Group III – Dual Rinse HEDP dissolved in ultra-pure water; Group IV – ultra-pure water, control), and incubating at 37°C for 48 hours to assess antimicrobial activity by measuring inhibition zones. The experiment was repeated in six independent experiments (n = 6 per group), and the data were analyzed with SPSS using the Shapiro–Wilk test, one-way ANOVA and Tukey’s post hoc test.
Results: The largest inhibition zones were recorded for 5.25% NaOCl (17.8 ± 0.9 mm), followed by Dual Rinse HEDP in NaOCl (16.3 ± 1.1 mm) and Dual Rinse HEDP in ultra-pure water (8.5 ± 0.6 mm); no inhibition was observed in the control group. The difference between NaOCl alone and NaOCl combined with HEDP was small (1.5 mm) but statistically significant (p = 0.027), and both NaOCl-containing solutions produced significantly larger zones than HEDP in water (p < 0.001).
Conclusion: Under the conditions of this agar diffusion model, the addition of HEDP to 5.25% NaOCl resulted in a small but statistically significant reduction of the inhibition zone against E. faecalis, while the mixture retained high antimicrobial activity. HEDP alone showed limited antimicrobial activity.
Keywords: Sodium hypochlorite, etidronic acid, HEDP, Enterococcus faecalis, antimicrobial activity, endodontic irrigants,
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Please cite this article as: Pecheva A, Georgiev K, Simeonova E, Boyadzhieva E, Dobrev I. Antimicrobial efficacy of sodium hypochlorite alone and combined with Dual Rinse HEDP against Enterococcus faecalis: an in vitro study. J of IMAB. 2026 Oct-Dec;32(4):7160-7164. [Crossref - 10.5272/jimab.2026324.7160]
Correspondence to: Aleksandra Pecheva, Department of Operative Dentistry and Endodontics, Faculty of Dental Medicine, Medical University of Plovdiv; 3, Hristo Botev Blvd, Plovdiv, Bulgaria. E-mail: Aleksandra.pecheva@mu-plovdiv.bg
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Received: 27 April 2026
Published online: 15 October 2026