A tooth whitening appliance includes an applicator having a soft moldable core covered by a plastic film membrane. The contours of buccal surfaces of target teeth to be whitened are impressed into the applicator by applying lateral pressure. A layer of tooth whitening preparation is deposited on the impressions formed in the applicator and the applicator is repositioned against the buccal tooth surfaces for the administration of the tooth whitening preparation. The applicator core is soft and moldable preferably at or below body temperature. The membranes support the applicator in reduced thickness impression areas. The applicator core may be optionally preloaded with tooth whitening preparation.