Influence of Ethylenediaminetetraacetic Acid on the Active Chlorine Content of Sodium Hypochlorite Solutions When Mixed in Various Proportions

Abstract

Introduction This study documented the time-related effect on active chlorine content of NaOCl solutions of different concentrations after dilution with ethylenediaminetetraacetic acid (EDTA) in various proportions. Methods Five NaOCl solutions (Milton, Black and Gold domestic bleach, and the surfactant containing products, White King and Hypochlor 1% and 4% forte) were mixed with EDTA in the following proportions: 90:10, 75:25, and 50:50. Changes in active chlorine content were determined at intervals between 5 and 18 minutes. Results Results were analyzed statistically by using general linear statistical models in SPSS. With the exception of White King solutions, EDTA substantially and rapidly reduced available chlorine even in small proportions, with loss being extreme at first and then more gradual. The reaction was exothermic. Results showed that White King mixed 90:10 lost on average only 8% of its active chlorine at its first measurement (approximately 5 minutes) but lost 36% of its active chlorine when mixed 75:25. The Hypochlor products at 90:10 dilution lost on average 27%–31% active chlorine during this time period. Mixing EDTA with NaOCl caused a dramatic loss of active chlorine for all solutions mixed 50:50. NaOCl solutions containing surfactant had less active chlorine loss for the 75:25 and 90:10 admixtures. Conclusions NaOCl and EDTA should not be present in the root canal at the same time if the therapeutic benefits of NaOCl are to be realized, but the order in which they should be used for endodontic irrigation remains a matter of debate.