A tooth whitening delivery system including a single-dose applicator and a liquid, substantially anhydrous tooth whitener composition of predetermined viscosity contained in said applicator for delivery of a tooth-whitening amount of active whitening ingredient from said applicator onto teeth, with effective bioadhesion and retention thereof, and, thereupon, sufficient penetration of said ingredient through the tooth enamel providing efficacious bleaching of stained teeth, comprising, by weight,
(a) 10% to 75% of a complex which is (i) a mixture of 78 to 90% of water soluble polyvinylpyrrolidone (PVP) having K-values of K-12 to K-120 and (ii) 10 to 22% of H2O2; releasing 1 to 20% of active H2O2 from said complex onto a tooth surface; (b) 0 to 20% of PVP K-60 to K-90, said PVP being present in said composition at a K-value of the PVP in said complex of less than 30, and/or the amount of PVP therein is less than 20%, and (c) 30 to 90% of a substantially anhydrous solvent, said composition having a Brookfield viscosity of 75 to 300 cps, an in vitro bioadhesion/retention on hydroxyapatite (HAP) of at least 10% after 5 minutes while immersed in water, and a bleaching efficacy defined by ΔE values of at least 5 in the CIE (L*a*b*) color scale.