Systems and methods for mixing an oral care formulation base with one or more oral care additives in-situ. In one aspect, the invention can be a method of making an oral care formulation for consumer use, the method comprising: a) providing a first dose of an oral care formulation base to an oral cavity of a test subject; b) dispensing one or more oral care additives to the oral cavity in accordance with a first dispensing regimen during the performance of step a), the one or more oral care additives mixing with the first dose of the oral care formulation base in-situ within the oral cavity of the test subject; c) obtaining feedback regarding effects experienced by the test subject during the performance of step b); and d) creating the oral care formulation for consumer use based, at least in part, on the feedback of step c).