In order to lighten a darkly discolored tooth that has had root canal therapy, internal, or non-vital, bleaching is used. A chemical oxidizing agent is placed within the coronal portion of a tooth to remove tooth discoloration.
 

This may be performed in the dental office, two procedures can be done.

One is 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.
Depending upon the discoloration of the tooth this may be done once or several times.

The other procedure is known as "walking bleach".
In this method, the bleach crystals that will be placed inside the tooth are left for several days and then the patient returns to the dental office to have the bleach crystals removed.
Also, this procedure may be performed one or more times, depending upon the discoloration of the tooth.