Effect of storage temperature on pH of in-office and at-home dental bleaching agents.

The aim of this study was to determine the pH of several commercially available in-office and at-home dental bleaching products stored at room temperature and refrigerated. The products were divided into in-office (n=09) and at-home (n=12) bleaching gels and submitted to two different temperatures, namely, room temperature (23 degrees C +/- 1 degree C) and refrigeration temperature (4 degrees C +/- 1 degree C). The pH was measured using a portable pH meter with a direct electrode, which was calibrated with standard buffer solutions at pH 4.0 and 7.0 and recalibrated for each new product. The pH of the dental bleaching products tested ranged from 2.39 +/- 0.10 to 6.52 +/- 0.09, and was found to vary significantly both with temperature and between bleaching agents. Most of the bleaching gels were found to be acidic, especially the in-office bleaching products, and the refrigerated at-home gels had the highest pH values. Thus, we conclude that the storage temperature affected the pH of the products tested.