•Purpose: to determine the minimum concentration of NaOCl that causes color change and precipitate formation when mixed with 2.0% CHX, and to characterize the resulting precipitate
•Materials & Methods:
•a serial dilution technique was used.
• 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 % NaOCl, respectively.
•To characterize the precipitate, a new set of six flat-top polypropylene microtubes were prepared with diluted concentrations of NaOCl (6.0%, 3.0%, 1.5%, 0.75%, 0.38%, and 0.19%) and 0.5 mL of 2.0% CHX was added.
•Color change occurred in all nine microtubes where CHX was added, including the one with lowest concentration of 0.023% NaOCl.
•As the concentration of NaOCl increased, the color range varied from peach to brown
•color change and the precipitate occurred immediately and showed no change with time.
•Both XPS and TOF-SIMS showed the presence of para-chloroaniline in an amount directly related to the concentration of NaOCl used.
The formation of the precipitate should be avoided by removing the NaOCl before placing CHX into the canal.