A root canal is usually needed if there is swelling around a tooth, a tooth aches on its own, or a tooth is extremely sensitive to hot or cold liquids or foods. Often, someone knows they need a root canal because it hurts to chew. This can be due to a crack in the tooth. Root canals are also necessary if the tooth has an infection due to decay, causing pain and swelling, When the nerve in a tooth dies for any of these reasons, it makes a root canal necessary.
During the root canal procedure, the canal is accessed and cleaned, and a rubber substance is gently packed into the canal space to seal against future infection.