The para-chloroaniline prevention after the use of sodium thiosulfate as an intermediary irrigator between sodium hypochlorite and chlorhexidine

Objective: Evaluating the neutralization of sodium hypochlorite (NaOCl) by sodium thiosulfate in vitro, in different concentrations, in the prevention of para-chloroaniline (PCA) formation when in contact with CHX. Material and methods: It were collected 2 mL of NaOCl solution to 2.5% and to 6%, divided in eight groups according to the sodium thiosulfate concentration (1.0; 2.5; 5.0; 10%) (TSF). The tests were done in duplicate and in each plate, it was poured 2mL of TFS and the reaction was observed for 5 minutes. After, 2 mL of 2% Chlorhexidine (CHX) were pouring on the plates to verify the formation of PCA. The infrared spectroscopy with Fourier transform was used to verify the presence of PCA, and, in each solution, the pH was verified with universal strip. Results: All analyzed samples presented presence of water and deuterium water, and there was not identification of the PCA presence. The pH result of the solutions was between 8 and 9. It was verified that in the increasing of the concentration of the TFS there was gradual formation of precipitated compound and increase of the turbidity of the final sample. Conclusion: TFS can be used as an intermediate irrigation solution to prevent the formation of para-chloroaniline in the combined use of NaOCl and CHX.