In-vitro Whitening Efficacy and Design of a New Peroxide Dentifrice

Objective: To formulate a stable and efficacious peroxide dentifrice.   

Method: Hydrogen peroxide stability – The dentifrice was aged in tube at two months 40 ºC.  After aging, the dentifrice was analyzed for active oxygen by a validated analytical method.

In-vitro whitening efficacy - 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.  Analysis of variance was used to compare the mean ΔW* value for each product with p<0.05 indicating significant differences between products.  

Result: Colgate® Optic White^TM, a dentifrice with 1% hydrogen peroxide, was formulated using a non-aqueous humectant/solvent system, polyvinylpyrrolidone, and calcium pyrophosphate which was identified as an abrasive system that is compatible with hydrogen peroxide.   This formulation not only stabilized 90% hydrogen peroxide in the tube during accelerated aging but in-vitro testing demonstrated that the formula delivered hydrogen peroxide upon brushing to effectively whiten teeth.  The new 1% hydrogen peroxide dentifrice (ΔW* = -8.5 ± 2.0) provided statically superior (p<0.0001) whitening efficacy to regular fluoride toothpaste, Colgate® Cavity Protection, (ΔW* = -2.7 ± 1.3) in a brushing model.

Conclusion: A new dentifrice containing hydrogen peroxide was developed in which the peroxide is stable and available to whiten teeth upon brushing.  The whitening efficacy was measured using an optimized in-vitro brushing model and was found to be superior to that of a regular fluoride toothpaste.