Why does a root canal treated tooth turn dark?

A tooth that has had root canal treatment gradually darkens because the nerve and blood vessels were removed, cutting off its supply of moisture and nutrients. It is a natural change that develops slowly over months to years after treatment. Options for improving it are 1) internal bleaching, in which a whitening agent is placed inside the tooth, and 2) a crown or laminate veneer to restore both color and shape when the discoloration is severe or the tooth is badly damaged. However, if the discoloration comes with swollen gums or pain when chewing, inflammation at the root tip may have returned, so please come in to have it checked.