Treatment compositions in the shape of a strip or patch include a substantially solid adhesive layer and a treatment gel. A barrier layer may be included on an outer surface of the adhesive layer to form a treatment strip. The adhesive layer comprises a substantially solid adhesive composition that has increased adhesiveness to oral tissue when moistened with saliva or water. The adhesive layer is formed from an intermediate composition that is heated to drive off the solvent. Using a treatment gel separate from the adhesive layer improves the potency and stability of an active agent that is sensitive to heat, as the treatment gel is typically not heated prior to use like the adhesive layer. The adhesiveness of the treatment composition or strip facilitates placement over a person's teeth. The moistened adhesive composition reliably adheres the treatment composition or strip against a user's teeth during a desired procedure. Because a substantial portion of the adhesive composition remains solid or semi-solid during treatment, the adhesive composition maintains a substantial portion of its adhesive properties and internal cohesive strength compared to, e.g., a treatment gel used by itself.