Treatment devices in the shape of a dental tray, strip or patch include a barrier layer and a protective adhesive composition. Treatment kits include one or more treatment devices and one or more treatment compositions that are initially separate from the treatment devices. The treatment compositions may be contained within a syringe (e.g., a unit dose syringe) for ease of delivery. The treatment composition is dispensed from the syringe onto the barrier layer and then placed over a person's teeth and/or gums. The protective adhesive composition, in combination with the barrier layer, at least partially confines the treatment composition to a desired location within the person's mouth during use. The barrier layer protects the treatment and protective adhesive compositions from saliva or moisture found in the person's mouth.