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.