Abstract: The present invention discloses high viscosity sustained release dental compositions, such as tooth bleaching or fluoride compositions, for treating tooth surfaces. For maximum results, an improved dental tray having reservoirs for holding the dental composition adjacent the desired tooth surfaces is preferably used in combination with the sustained release dental composition. The sustained release dental compositions include a high carboxypolymethylene concentration which results in very high viscosity. The high level of carboxypolymethylene makes dilution of the dental compositions from saliva difficult and time consuming so that the compositions stay within the tray reservoirs, thereby providing sustained release. The concentrated carboxypolymethylene adds a unique tackiness to the dental composition which helps retain and seal the soft tray material against the patient's teeth.