Endodontics is the specialized field of dentistry that deals with the diagnosis, management and treatment of the infected dental pulp/nerve of the teeth, the surrounding gums and bony tissue. It is commonly known as root canal treatment.
Endodontics is needed when you have a toothache, i.e. there is pain associated with your teeth, a condition known as acute pulpitis. This arises when the pulpal tissue/nerves of the teeth are inflamed due to a variety of factors like decay, trauma, large and deep fillings or insults to the tooth.