A clinical trial was conducted to evaluate the peroxide degradation and dilution kinetics of Crest Whitestrips Supreme, a whitening strip carrying a low, fixed amount of a 14% hydrogen-peroxide bleaching gel. Crest Professional Whitestrips–a 6.5% hydrogen-peroxide strip with a well-established clinical efficacy and safety profile–served as the positive experimental control. A total of 17 healthy adults were enrolled in the crossover study (subjects used both products, and each product was used 4 times by each person). Test strips were applied to the maxillary arch, after which hydrogen-peroxide concentration was measured on the strip, teeth, gingiva, and in saliva over a 60-minute period using standard analytical methods. Treatments were compared at individual time points, and overall using the area-under-the-curve (AUC) calculation of total hydrogen-peroxide exposure (concentration over time). For the higher-concentration strip, hydrogen-peroxide concentration from the strip and teeth samples dropped initially at the 5-minute sampling point, then slowly declined over time. At 30 minutes–the nominal treatment time for these 14% hydrogen-peroxide strips–the median hydrogen-peroxide concentration was 6.2% on the strips and 4.4% on the teeth. In contrast, the gingival and salivary hydrogen-peroxide concentrations were already low and/or below the level of detection by 5 minutes, and remained low throughout the sampling period. Treatments generally differed (P < .001) with respect to hydrogen-peroxide concentrations on the strip and teeth, but not on the gingiva or in the saliva. AUC cumulative measurements through 60 minutes demonstrated 77% higher hydrogen-peroxide levels on teeth for the 14% hydrogen-peroxide strip compared to the 6.5% hydrogen-peroxide strip. This research demonstrates the feasibility of vital bleaching with an exceedingly thin layer of 14% hydrogen-peroxide gel, with little gingival or salivary hydrogen-peroxide exposure.