Endodontics is a field of dentistry that deals with the diseases of the tooth nerve.
The inside of the tooth contains the “dental pulp“, which consists of vessels and nerve fibres.
The pulp extends from the crown of the tooth into the roots and communicates with the surrounding tissue via the root tips.
Disease of the endodont (the inner part of the tooth) is manifested by inflammation or infection of the root canal system that contains the dental pulp. In popular parlance, this is called “a toothache”