Dental bleaching compositions, for example in the form of liquids, gels, creams, pastes and ointments, comprising a peroxide releasing compound and from 1% to 35% by weight of a potassium-containing compound such as potassium nitrate, wherein the potassium nitrate is present in a safe and effective amount to prevent tooth hypersensitivity in the patient during the bleaching process. The potassium nitrate contemplated by the invention is compatible with peroxide yielding bleaching compounds such as peroxide, carbamide peroxide, calcium peroxide, zinc peroxide, magnesium peroxide and sodium perborate. Potassium nitrate is complimentary and synergistic with the peroxide bleaching agents contemplated by the invention and enhances the release of oxygen to the tooth enamel. Also contemplated are methods of bleaching teeth comprising application of the dental bleaching compositions of the invention.