A tooth that has had root canal therapy, because of trauma or decay, tends to darken over the years. These teeth do not respond to conventional whitening procedures because the change in color is intrinsic rather than extrinsic.
When a root canal is performed it requires the removal of unhealthy or damaged pulp tissue in the canal located inside the root of the tooth. As a result, the dentin (the substance which enterprises most of the tooth structure) is now devoid of living tissue and often tends to discolor. This is caused by blood pigments that are left from the pulp or sometimes by the material used to fill root canal. This discoloration is also visible in teeth that have been traumatized and in which an internal hemorrhage has occurred.
Bleaching a tooth with a root canal can not be done with conventional whitening procedures because these work by whitening the enamel which covers the outside of the tooth. Bleaching a devitalized tooth can only be performed by your dental professional. This is done by placing a bleaching agent directly into the empty pulpal chamber.
The most common bleaching agent is sodium perborate. Sodium perborate is a hydrogen peroxide, that when mixed with hydrogen peroxide accelerates the change of color. This procedure resembles the lightening of hair shafts when bleaching hair in a beauty salon.
The clinical steps are the following:
1) An x-ray must be taken prior to treatment to ensure that the root canal filling material is still intact. It is also important to verify the surrounding bone structure to make sure that it is healthy.
2) A small opening is made at the back of the tooth where the original access for the root canal treatment had been made. No new tooth structure has to be sacrificed. This space is then cleaned of debris and stain.
3) The top end of the root canal is then sealed with a special cement. This is done to prevent the bleaching agent from seeping into the root canal filling.
4) The sodium perborate paste is then inserted into the cavity and covered by a temporary filling. Care should be taken to make sure this filling is properly sealed in order to prevent the bleaching agent from leaking into the mouth. This procedure is then repeated every 3-7 days until the desired results are achieved.
5) Once satisfied with the results a permanent filling is placed. This is required in order to perfectly seal the access cavity once again.
Although this clinical procedure usually has very satisfactory aesthetic results, there is the odd case where, even after several repetitions, a tooth no longer responds to the treatment. In cases such as these, there are alternatives such as porcelain veneers or crowns which can be used to mask these discolored teeth.