pH variation among materials used for intracoronal bleaching

Intracoronal bleaching of pulpless teeth with 30% hydrogen peroxide may result in external cervical root resorption. One of several suggested etiological factors associated with this complication is the pH of the bleaching materials. Because the available data on the pH values of bleaching materials were conflicting, it was the purpose of this study to measure the pH of the materials commonly used for bleaching pulpless teeth. The pH of different concentrations of sodium perborate and 30% hydrogen peroxide, alone or in combination, were measured for a period of 14 days. Sodium perborate was confirmed to be alkaline, whereas 30% hydrogen peroxide was acidic. The pH of the materials when mixed together gradually changed from acidic to alkaline as the concentration of sodium perborate was increased. A thick clinical consistency mixture of both materials was alkaline, and its alkalinity increased with time. These results do not support the theory relating bleaching-induced root resorption to an acidic pH of the bleaching pastes.