Can you bleach a single darkened tooth?

Most darkened front teeth have diminished or no vitality. If they have had succesful endodontic therapy and a patient does not desire a crown or a porcelain veneer, sometimes they can be successfully lightened using a 16% Nitewhite carbamide bleaching gel in a standard custom bleaching tray. The procedure is as follows: The filling used to cover the endodontic access opening is removed and the gutta percha that is visible inside is sealed with a modified glass ionomer material (I use Vitrabond). Then the patient is instructed to place the gel at night in the tray, but only for the reservoir that corresponds to the darker tooth. I have my patient do this for a week and then return for me to check. I believe this result took two weeks. Although the area near the gingiva is still amber colored, the rest of the tooth lightened nicely. My patient was extremely happy. I place IRM in the access hole and have asked my patient to return in another two weeks in order to make sure the result is stable. If it is, I will place a composite filling in the access to seal it more permanently.