For medical tooth whitening, with custom trays. This method is especially appropriate when internal discolorations have to be treated intensively, e. g. after the use of tetracycline. After impressions, custom trays are made and filled with 45% carbamide peroxide gel and placed on the teeth. During the treatment time (about 30 min.), the patient can stay in the waiting room of the dental office. The high viscosity gel does not leach, but stays in the tray whitening the stained teeth.