There are several possible reasons why your tooth is darkening. During the process of removing the nerve (pulp), some very small particles of blood or tissue may have been left in the tooth. Over time, these darken.

Sometimes, the materials used in the root canal material (the sealer, which may contain metals) can discolor the tooth. Sometimes, the composite used to close the hole in your tooth may not seal the area perfectly. If your tooth gets small cracks in it, coffee, tea, and food may get into the spaces and stain the tooth.

There are a number of ways to treat the tooth. If it is in good condition, the composite material and other filling material can be removed. Then, a small piece of cotton that contains a whitening (bleaching) agent can be place inside the tooth for a number of days. This process can be repeated until the internal stain disappears. If this approach does not work, the tooth can be restored using a crown made of porcelain or porcelain over metal. If the bleaching does not get the tooth as white as you would like, you could have a porcelain veneer placed on the tooth. This is a thin layer of porcelain that covers just the front of the tooth.