A root canal fundamentally changes the internal structure of your tooth, but this is definitely a change for the better. The inflamed, irritated (and irritating) dental pulp inside the tooth is removed, and the empty pulp chamber is then filled with a biocompatible filling material, such as gutta-percha (a type of latex). All these changes are focused on the interior of the tooth, so why does the exterior of a tooth sometimes also change after a root canal?
Some patients might notice a change in the color of a tooth that has received a root canal. The tooth can darken and discolor, and the precise reasons for this are not known. It's speculated that the internal addition of the filling material can be visible on the tooth's exterior. Dental pulp also somewhat pressurizes a tooth, and when the pulp (and the pressure it creates) is removed, it's thought that discoloration from food and drink can start to make its way through to your dentin (which is the part of the tooth beneath the surface enamel). Regardless of the reason, you're probably more interested in how the issue can be corrected.
Filling and Crown
After your root canal, you would have received a provisional filling, which closes the access cavity the dentist made to access the dental pulp. Some patients will then receive a permanent filling, once the root canal has had sufficient time to settle. When the state of the tooth means that a filling won't be sufficient to stabilize its structure, a dental crown might be needed, in addition to the permanent filling. So if your tooth should discolor while your provisional filling is in place, it can be capped with a dental crown, which will entirely disguise any discoloration.
Of course, a tooth that has undergone a root canal might discolor after a permanent filling has been fitted. You can talk to your dentist about receiving a dental crown, but this can be an unnecessary expense when it's not needed for stabilization. Instead, ask about a dental veneer. This is a thin porcelain shell fitted to the outward-facing surface of a tooth and conceals any imperfections (such as discoloration).
Although discoloration to a tooth following a root canal is the result of a medical procedure, the solution will be a cosmetic one. Be sure to tell a dentist if your tooth begins to darken after a root canal. It's not cause for alarm, and a dentist will be able to discuss your options with you.