If the tooth decay has reached and involved the nerve in the centre of the tooth (tooth pulp), then toothache usually results and is usually irreversible. The pulpal tissue usually dies and if left untreated, will lead to infection spreading through the canal system of the tooth root to the bone tissue at the apex of the tooth roots and the jaw. Root Canal treatment (Endodontics) involves the cleaning, shaping, medication and sealing of the root canal system to prevent the spread of infection and to allow the root to continuing providing support to the tooth crown or artificial crown.

Sometimes, the tooth pulp is affected through traumatic fracture, tooth cracks or leakage under existing dental fillings. Often teeth that have received root canal treatment discolour with time and bleaching of these discoloured teeth is an option.

Routinely, posterior teeth that have received root canal treatment will also require crowns to provide coverage to prevent possible fracture or splitting of the tooth from the heavy biting loads at the back of the mouth.