Interaction between sodium hypochlorite and chlorhexidine gluconate

The combination of sodium hypochlorite (NaOCI) and chlorhexidine (CHX) results in the formation of a precipitate. The aim of this study was to determine the minimum concentration of NaOCI required to form a precipitate with 2.0% CHX. This was accomplished with a serial dilution technique. X-ray photon spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to qualify and quantify the precipitate. A color change and precipitate were induced in 2.0% CHX by 0.023 % and 0.19 % NaOCI, respectively. Both XPS and TOF-SIMS showed the presence of para-chloroaniline in an amount directly related to the concentration of NaOCI used. Until this precipitate is studied further, its formation should be avoided by removing the NaOCI before placing CHX into the canal.