We all know that teeth have roots. But did you know that there are
small canals inside the roots? Teeth are not composed of living tissue;
the only vital (or "living") part of a tooth is the pulp in the center.
Pulp is the soft tissue which contains blood vessels, nerves, and
connective tissue in the canals and the center of the tooth. These
nerves and blood vessels connect to the rest of the body at the tip of
the roots.
Cavities and trauma can lead to pulp irritation, which in turn leads
to pupil infection. This infection eventually manifests itself in
painful swelling.
Root canal treatment is the removal of all the pulp/nerves in the
tooth so that the tooth pain is no longer transmitted to the brain. A
filler material is inserted to seal the root canal from the surrounding
tissue.
A tooth that has had the pulp removed can continue to function for a
life time. However it does become more brittle over time. A "crown" is
often placed over a root canal treated tooth to protect it from
breakage.