Labeled Versus Actual Concentration of Bleaching Agents

Objective: The purpose of this study was to determine if the actual concentration of bleaching agents available in four different countries was different than what is indicated on the label and within the recommendations of the International Organization of Standardization (ISO).  Methods: The method recommended by the United States Pharmacopeia (USP) for assaying peroxide, utilizing trituration of sodium thiosulfate, was used to determine the actual bleaching agent concentration of the products.  Results: Seventy products were assayed.  Of the bleaching agents tested, ninety-one percent in the United States, seventy-seven percent in China, forty-seven percent in Brazil and fourteen percent in Saudi Arabia were within 15% of the concentration indicated on the label.  Additionally, nine percent in the United States, twenty-three percent in China, thirty-three percent in Brazil and seventeen percent of the tooth whitening agents in Saudi Arabia had a difference in the bleaching agent concentration that was greater than 15% but less than 30%.  Twenty percent in Brazil and fourteen percent of the tooth whitening products in Saudi Arabia were assayed to have greater than 30% concentration loss of active agent indicated on the label.  Ninety-two percent of the bleaching products in the United States in the month of expiration were within requirements established by the International Standard on Tooth Bleaching products, which requires at least 70% concentration of that indicated on the bleaching agent label.  Conclusions: All products in the United States and China were within the established standard; one product in Saudi Arabia and three products in Brazil had greater than 30% concentration loss when products were tested immediately upon delivery at testing sites.  Three of the 24 products in the United States had greater than 30% concentration loss than the label indicated when they were tested at the month of expiration.