One of the most common causes of discoloured teeth is due to a 'dead tooth' or a tooth that is root filled. All of our teeth are supplied by nerve and blood supply. Now when a tooth needs a root canal treatment, this supply called the pulp is removed which can lead to the deposition of blood products within the tooth which is then absorbed by the tooth leading to a darker colour. On a back tooth, this may not have any major issue but on a front tooth is a different matter altogether!
 

Our case of the month for July involves a treatment to whiten a discoloured lower front tooth. We will often come across darker teeth when they have undergone a root canal treatment due to the loss of the nerve and blood supply. Often the degradation of blood products from the pulp tissue within the dentinal tubules cause the tooth dentine to be gradually discolour and give that inherent grey/ dark appearance. This can be quite unsightly especially on a front tooth. For back teeth, in almost every case, we will need to place a crown once a tooth has been root filled to maintain function. This will also improve the colour as the ceramic cover the dark dentine. However, for front teeth, crowns are not always needed as the access for the treatment is on the inside of the tooth and when done under microscope, can be extremely minimal. So how do we whiten the tooth?
 

One of the main aesthetic challenges we face as dentists, is a dark discoloured front tooth. This usually results from after a root canal treatment which may be needed for a variety of reasons but is usually from trauma. The reasons for the discolouration do vary. This could be from remnants of the pulp tissue being left within the root canal system and then decomposing within the tooth permeating into the dentine. There can also be rupture of the blood vessels within the pulp allowing blood products to seep into the dentinal tubules and discolour the tooth as this degrades. Another common reason is not so well known. Studies have shown that another factor could be the result of not removing all of the root canal sealant material once the tooth has been treated. van der Burgt TP, Mullaney TP, Plasschaert AJ. Tooth discoloration induced by endodontic sealers. Oral Surg Oral Med Oral Pathol. 1986;61:84–9. [PubMed] [Google Scholar] [Ref list]

The chromophores resulting from the disintegration of root canal sealer remnants penetrate through the dentinal tubules into the coronal tooth structure gradually causing progressive discoloration. The key factor is that most root treated teeth do appear darker than non root treated teeth and when this is on a front tooth, it is a major aesthetic issue.