Endodontics is a form of dentistry concerned primarily with the roots and soft tissue below the tooth. Root canals are required when the pulpy portion of the tooth in the roots become diseased.
The surface of the tooth may still be healthy, but the roots are not. The diseased pulp is removed from below the tooth by accessing an opening through the tooth. Infection of the pulp is usually quite painful and can cause swelling or inflammation.
"Root canal" has become a scary term for dental patients to hear, but the benefits of the procedure and advances in dental technology have made it much less "scary". Local anesthetics and proper pain medication allow the procedure to be performed with little or no pain in most cases. There may be some soreness following the procedure, but that is normal for most dental procedures. Over the counter medications are usually enough to relieve any pain afterwards. The procedure will also relieve you from pain caused by the infection.