A method for brightening of teeth is described, using a kit with the componentsA an alkaline, aqueous sodium fluoride solution, containing a gel former,B a dried gel, present in film strips, containing B1 at least one gel former, B2 phosphate or hydrogen phosphate ions, B3 optionally at least one amino acid, B4 optionally fluoride, B5 optionally glycerol, B6 optionally a carboxylic acid or a buffer system for one of the pH values from 4 to 7. C a dried gel, present in film strips, containing C1 at least one gel former, C2 calcium ions, C3 optionally glycerol, as well as preparation of the kit.