The soft tissue, or pulp,  that lives inside each tooth contains blood vessels, tooth-forming cells, connective tissue and nerve fibers.  The health of this tissue depends on the integrity of the tooth that surrounds it, and the blood supply that comes through the tips of the roots.  When there is a break in the tooth structure, bacteria invade the pulp and the blood supply cannot supply enough nutrients, and the pulp becomes inflammed or infected.

Treatment consists of removing the tissue from the inside of the tooth, shaping and cleaning the pulp spaces, and filling with a sterile material and sealant.  The tooth that requires root canal often needs a crown to restore and protect it afterwards.