Molecular interactions between the most commonly used endodontic lavage agents in clinical practice

Abstract

Aims The aim of the present study was (i) to analyze the molecular interactions after mixing ethylenediamine tetra-acetic acid (EDTA) and sodium hypochlorite solutions using spectroscopic methods, (ii) to analyze the interaction after experimental cold plasma energy transferring mimicking physicochemical activation of solutions. Methods Freshly opened pharmaceutical lavage solutions of 5.25% hypochlorite (pH= 9.35) and 17% EDTA (w/v; pH=7.32) were used in experiments. Mixture of 40 ml was prepared using 5.25% hypochlorite / 17% EDTA at a 1:1 ratio. The experimental cold atmospheric-pressure argon plasma jet treatment was performed using a dielectric barrier discharge device for mimicking the activation of lavage solutions. Spectral changes were analyzed with Fourier-transform infrared spectroscopy and ultraviolet-visible spectrophotometry. Results The main findings were that carbon and nitrogen bonds formed on the EDTA molecule at 2356.99 cm-1 and 2309.00 cm-1 after oxidation with hypochlorite. The newly formed peaks corresponding to carbon-nitrogen on the oxidized EDTA molecule were disappeared after the experimental atmospheric-pressure argon plasma jet treatment. Due to stimulation at a higher energy level, π-π* electronic transition was towards the bathochromic shift whereas, n-π* electronic transition was towards the hypsochromic shift. Conclusions The molecular structure of EDTA was observed to change after the oxidization by hypochlorite. The subsequent molecule occurred by the oxidization by hypochlorite or activated hypochlorite is different from each other and also is different from the characteristic structure of EDTA. Experimentally activated hypochlorite was observed to cause the molecular electronic transitions of EDTA. Thus, the interaction of EDTA and hypochlorite is more complex than the previously described theory.