Crest Whitestrips are thin, liquid films adhered to a plastic exterior that can be applied directly to the tooth, enabling mass transfer of its active ingredient, hydrogen peroxide, to penetrate the tooth outer layer. The tooth outer layer consists of enamel and dentin. The goal of this study was to model the concentration of hydrogen peroxide as it moves through the gel tooth outer layer for a period of 30 minutes. GAMBIT was used to create a two-dimensional mesh modeling the three layers through which the hydrogen peroxide diffuses through: the gel, enamel and dentin. FIDAP was then used to model the process in which hydrogen peroxide moved through these three layers. A sensitivity analysis was performed varying the diffusion coefficients and reaction rate of hydrogen peroxide being used up. It was found that accurate values for all of these properties must be obtained in order to determine an accurate solution.