There are various reasons why a tooth may need root canal, some of which include infection, trauma, deep decay, positioning of the tooth, etc. Endodontic (Root Canal) treatment is a method of retaining the tooth by removing the nerves in the tooth. It involves the cleaning, shaping and filling of the canal space within the root of the tooth.
Retreatment is necessary when the root canal becomes re-infected. It is usually possible to perform the root canal treatment again and create an environment which will promote healing.