In-Vitro Whitening Efficacy of Peroxide Dentifrices

Objective: To evaluate the in-vitro whitening efficacy of Colgate® Optic White™ toothpaste containing hydrogen peroxide to commercial toothpaste containing urea peroxide, Rembrandt® D. 

Method: In-vitro brushing study - Artificially stained bovine teeth were polished with prophylaxis paste until initial L*, a*, and b* values approached those of human teeth.  The teeth were brushed for two minutes with a dentifrice slurry, rinsed with water, and L*, a*, and b* values were collected with a spectrophotometer.  This process was repeated a total of 14 times to model one week of brushing.  A whiteness index, ΔW* (where W*=((L*-100)²+a*²+b*²)^1/2) was reported after 14 brushing treatments.  Bleaching efficacy – Saliva coated hydroxyapatite disks were soaked in a coffee, tea, and wine staining solution for 2 hrs.  Baseline L*, a*, and b* values were measured with a spectrophotometer.  Each disk was soaked in freshly prepared dentifrice slurry for 2 min and rinsed with water.  This process was repeated a second time and L*, a*, and b* values were measured with a spectrophotometer.  Analysis of variance was used to compare the mean ΔW* value for each product with p<0.05 indicating significant differences between products. 

Result: After 14 brushing treatments, the ΔW* (-8.2 ± 1.2) for the hydrogen peroxide dentifrice was statistically superior to the ΔW* (-6.3 ± 2.1) for the urea peroxide dentifrice (p=0.0221).  In the bleaching experiment, the ΔW* (-17.6 ± 1.3) for the hydrogen peroxide dentifrice was statistically superior to the ΔW* (-11.1 ± 1.3) for the urea peroxide dentifrice (p<0.0001).

Conclusion: A new whitening dentifrice with hydrogen peroxide delivers superior in-vitro efficacy to a commercial whitening dentifrice containing urea peroxide.  Greater whitening efficacy was measured in studies with and without brushing, highlighting the superior overall whitening efficacy of the product, as well as the bleaching efficacy of the peroxide component, respectively.