In-Use Peroxide Kinetics of a Hydrogen Peroxide Whitening Dentifrice

Objective: This study was conducted to evaluate in-vivo hydrogen peroxide kinetics of a hydrogen peroxide containing whitening dentifrice.  Method: Seven generally healthy adult volunteers were enrolled into the study.   Each subject brushed with a pre-measured amount of paste for a specified brushing time of either 15 or 30 seconds in random order.  After brushing, expectorate was captured into a beaker of 100 ml of 0.1M sulfuric acid to immediately stop further salivary decomposition of peroxide and stabilize the hydrogen peroxide for analysis.  Subjects then quickly rinsed with 20 ml of deionized water to capture any residual peroxide in the oral cavity.  Rinse expectorate was captured into a separate beaker of 100 ml of 0.1M sulfuric acid to stop further decomposition reactions.  After brushing, the brush head was immediately rinsed in sulfuric acid solution to capture any residual peroxide in the bristles.  The solutions were then titrated for peroxide content using an indirect iodometeric titration technique. Samples from the tube of paste used in this study were also analyzed for hydrogen peroxide concentration using this iodometric titration to establish the starting concentration and dose.   Result: The average baseline hydrogen peroxide concentration in neat dentifrice was 0.96% (s.d. 0.028%).  Average expectorate concentrations were 0.18% (s.d. 0.08%) and 0.05% (s.d. 0.03%) after 15 seconds and 30 seconds of brushing respectively.  The dose of paste used at each brushing was 1.2 grams representing an initial dose of 11.3 mg of hydrogen peroxide.  Average re-captured peroxide amounts were 2.56 mg (s.d. 1.67) and 1.02 mg (s.d. 0.38) after 15 seconds and 30 seconds of brushing respectively.  All measurements significantly differed from baseline p<0.05.  Conclusion: Short term use of a labeled 1% hydrogen peroxide whitening dentifrice yielded a rapid decline in peroxide concentrations in expectorant slurry and a commensurate rapid decline in re-captured peroxide amount.