Abstract: Iontophoretic devices for treating dentin hypersensitivity are provided. One device includes a housing, an electric current source, and a replaceable cartridge mounted to or in the housing. The cartridge includes (1) a container containing an iontophoretic solution and (2) an applicator assembly fixed to the container. The assembly has a tip portion that is in electrical and fluid communication with the solution. Also provided is an iontophoretic toothbrush that includes an applicator assembly that has a brush with improved bristles.