Endodontics is the specialty that is geared towards treating the nerves within the teeth.  Root canal treatment includes removing the nerve from the pulp chamber and canals as well as removing any infection or debris that have infiltrated these areas.  After the canals have been cleaned, a medication is placed along the length of the canals and the space is sealed with a flexible material called gutta percha.  Upon sealing the canals, the prepared area is then sealed to its original height with some restorative material (called a core build-up) and in many cases the tooth is then crowned.  The purpose of all these steps is to seal the root canals and internal tissues from the outside oral environment while also giving the tooth the best prognosis for long-term stability and survival.

For more information follow the link below

https://www.mouthhealthy.org/en/az-topics/r/root-canals