Inside a tooth is a small, fine space called the root canal. This canal contains dental pulp which consists of nerves and blood vessels. When the dental pulp is infected or the nerve has died the tooth can become painful and/or an abscess may develop. 

There are a number of conditions that can lead to irreversible damage of the dental pulp, including: decay, deep fillings, trauma, breakages and infection and sometimes there is no apparent cause. Root canal therapy is generally done in two stages. In the first stage the nerve and pulp are removed and the canals are washed with a sterilizing solution and temporarily filled. This gives the tooth time to heal if it has abscessed. The second stage is to permanently fill the canals once they have healed. This is generally 6-8 weeks after the first stage. Root canal treatment can often save a tooth which, if extracted, could require more extensive treatment for the rest of the mouth in the future.