|  | Internal, 
                    or non-vital, bleaching is used to lighten a darkly discolored 
                    tooth that has had root canal therapy. 
                    A chemical oxidizing agent is placed within the coronal portion 
                    of a tooth to remove tooth discoloration. It may be performed 
                    in the dental office using a procedure known as "chair 
                    side bleach." In this procedure, bleach crystals are 
                    placed inside the tooth, left for a period of time, and then 
                    removed before leaving the office. This may be done once or 
                    several times, depending upon the discoloration of the tooth. 
                    Another method is known as "walking bleach". In 
                    this procedure, bleach crystals are placed inside the tooth, 
                    left for several days and then the patient returns to the 
                    dental office to have the bleach crystals removed. Again, 
                    this procedure may be performed one or more times, depending 
                    upon the discoloration of the tooth. 
                     
                      |  |  |   
                      | before 
                          non-vital bleaching | after 
                          non-vital bleaching |  |