Endodontics is the field of dental medicine aimed at preserving teeth by means of the prevention, diagnosis, treatment and monitoring of changes to the dental pulp (nerves and other tissues inside the tooth) and the tissue around the roots. Commonly known as devitalisation or root canal surgery, endodontics is a conservative form of treatment carried out when the pulp is inflamed or does not show signs of life. The space occupied by the pulp is cleaned, and filled with biocompatible material to promote sealing of the dental canals, and prevent, or at least obstruct, the entry of bacteria. Normally root canal surgery is performed over two or three sessions. After the tooth is devitalised, it is restored by using a crown or other restorative technique that enables functionality to be restored. If treatment is not carried out the tooth will need to be extracted.