Internal, or non-vital, bleaching is used to lighten a darkly discolored tooth that has had root canal therapy. A chemical oxidizing agent (Sodium Perborate) is placed within the coronal portion of a tooth to remove tooth discoloration. Specific shades cannot be guaranteed.  If a specific shade is desired, a restoration such as a veneer or crown may be better.  However, internal bleaching gives the tooth the best chance of becoming its most natural tooth color.