Authors: Harrison JW, Hand RE.
Title: The effect of dilution and organic matter on the anti-bacterial property of 5.25% sodium hypochlorite.
Journal: J Endod
Date: Mar 1981
Citation: 7(3):128-32
Category: Irrigants and Medicaments
Evidence-based Ranking: 5
Purpose/Objective: To evaluate the effect of dilution on the antibacterial property of NaOCl and the effect of organic matter on the anti-bacterial property of 5.25% NaOCl. (against Streptococcus faecalis)

Materials and methods: Absorbent points were contaminated with Streptococcus faecalis and exposed for varying time intervals (5, 10, 30, 45, 60, 90 seconds and 2, 5, 15 minutes) to the following solutions: 5.25% NaOCl (Chlorox), 2.5% NaOCl, 1% NaOCl, 0.5% NaOCl and 3% hydrogen peroxide in equal volumes and normal saline solution (0.9% NaCl solution). After exposure to one of the test solutions used, the absorbent points were placed in culture medium and incubated, and the presence of growth was then recorded.

Results: 5.25% NaOCl was the most effective antibacterial agent against E. faecalis. Dilution of 5.25% NaOCl significantly inhibits its antibacterial property. Normal saline solution and a solution formed by equal volumes of 3% hydrogen peroxide and 1% NaOCl showed no antibacterial effectiveness. The presence of human serum albumin did not inhibit the antibacterial property of 5.25% NaOCl.

Conclusions: 5.25% NaOCl was the most effective solution and dilution of this solution inhibits its antibacterial property significantly. The presence of organic matter reduced the antibacterial property of 5.25% NaOCl.

ReviewerÂ’s comments: Classic article justifying the use of 5.25% NaOCl for efficacious antibacterial action (45 seconds). Also, 2.5% NaOCl can be used if the irrigant is given enough time inside the canal. (2 minute exposure of the paper point in the experiment)