A tooth whitening method uses an application device having a reservoir containing an oxidizing composition comprising a fluid carrier and an oxidizing agent, an applicator member in fluid communication with the reservoir, and a dispensing mechanism for moving contents of the reservoir into the applicator member. The oxidizing composition is dispensed into the applicator member by actuating the dispensing mechanism and is applied to one or more teeth in an oral cavity. Then, a sealant composition is applied to the teeth having the oxidizing agent thereon to form a coating that resists moisture contamination of the previously applied oxidizing agent. One embodiment uses an oxidizing composition with a viscosity less than 150 cps that is absorbed in a porous material in the device reservoir, from which it is introduced by capillary action into a porous applicator member.