19 May 2023

---

Interactions between calcium hypochlorite and irrigants commonly used in endodontic practice

---

Introduction

This study aimed to identify possible products resulting from chemical interactions between calcium hypochlorite [Ca(OCl)2] and other irrigants for endodontic use using electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOF-MS).

Methods

The 5.25% Ca(OCl)2 was associated with either 70% ethanol solution, distilled water, saline solution (0.9% sodium chloride), 5% sodium thiosulfate, 10% citric acid, 17% EDTA, or 2% chlorhexidine (CHX). The reaction ratio was 1:1 and the products obtained were analyzed by ESI-QTOF-MS.

Results

The interactions between Ca(OCl)2 and CHX generated an orange-brown precipitate, without identification of para-chloroaniline (PCA), and between Ca(OCl)2 and sodium thiosulfate a milky-white precipitate. Furthermore, when the oxidizing agent was associated with EDTA and citric acid, chlorine gas was released. As for the other associations, 70% ethanol, distilled water, and saline solution, no precipitation or gas release occurred.

Conclusion

The orange-brown precipitate occurs due to the chlorination of guanidine nitrogens, and the milky-white precipitate is due to the partial neutralization of the oxidizing agent. The release of chlorine gas occurs due to the low pH of the mixture, which results in the rapid formation and decomposition of chlorine. In this context, an intermediate rinsed with distilled water, saline solution and ethanol between Ca(OCl)2 and CHX, citric acid and EDTA seems to be appropriate to prevent the formation of by-products when these irrigants need to be used in the canal. Furthermore, if it is necessary to use sodium thiosulfate, a larger volume of the solution must be used than that used for the oxidizing solution.

Sidnei Flores de Pellegrin et al. "Interactions between calcium hypochlorite and irrigants commonly used in endodontic practice: a chemical analysis." Journal of Endodontics. 11 May 2023. DOI:https://doi.org/10.1016/j.joen.2023.05.003