If you have a severely damaged, decaying tooth or a serious tooth infection (abscess), your dentist may recommend a root canal treatment. Root canals are used to repair and save your tooth instead of removing it.
The pulp is soft tissue inside your tooth that contains nerves, blood vessels and provides nourishment for your tooth. It can become infected if you have:
If untreated, the tissues around the root of your tooth can become infected. When this happens, you will often feel pain and swelling and an abscess may form inside the tooth and/or in the bone around the end of the root of the tooth. An infection can also put you at risk of losing your tooth completely because bacteria can damage the bone that keeps your tooth connected to your jaw. Source