At the center of the tooth we find the pulp.  The pulp is composed of blood vessels, nerve tissue and other connective tissue, such as collagen.  It is the soft, inner portion of the tooth.

When decay, a crack, a leaking restoration or some other problem allows bacteria to find its way into the pulp of the tooth, the tooth responds like any other cut in the body would--it swells.  Swelling in the pulp, however, causes problems, for inside a hard tooth, the pulp has no where to swell to.  This creates pressure inside the pulp chamber and it results in pressure on the nerves, and pressure on nerves makes them hyper-excitable.  Teeth with swollen pulp tissue are said to be hyperemic, or inflammed.  This state is characterized by pain within the tooth.  This pain can be brought about when cold strikes the tooth or when heat touches the tooth.  The temperature change causes a slight expansion or contraction of a swollen pulp and this fires the nerves that are under pressure.

Once bacteria make there way to the pulp, they find a good source of food.  This allows the bacteria to grow and multiply.  Left unchecked, the bacteria will eventually kill the pulp.  Heavy swelling creates so much pressure that it prevents blood from flowing into the tooth.  The little blood vessels are literally crush closed.  This unfortunate situation allows the bacteria to win the battle and eventually all the pulp tissue will die.  This condition is called pulpal necrosis.

Given enough time, a necrotic tooth will begin to form an abscess deep in the bone.  This happens because the root canal ends at the tip of the root with an opening--the apical foramen.  This allows bacteria to get into the sterile bone and hence, an abscess is born about the root tip.  This abscess can create pressure.  As pressure build at the root tip the tooth begins to hurt when it is chewed on or tapped on.

To treat the infected tooth, one has two choices: Extraction or Root Canal Therapy (also called Endodontic Therapy)  In endodontic therapy, the tooth is opened on the chewing surface down into the pulp chamber.  Once opened up, the pulp can be removed from within the tooth.  Once removed, the inside of the tooth is disinfected, cleaned and shaped so that the canals are round at the tip.

Once the canals are cleaned and shaped, they are dried and a gutta percha point is cemented in the canal--right to the root tip opening.  This procedure closes up the apical foramen and bacteria can no longer get to the bone to cause an abscess.

The x-ray to the left shows how a root canaled tooth appears on a radiograph.  The gutta percha filling material on the inside of the root canal space, holds back x-radiation and the film remains clear in those areas.

This filling material--gutta percha--is a pink colored, rubber-like material that not only seal the canal well, it can be melted and ground out if necessary to re-treat the rooth canals.

Older root canals used to be filled with silver points.  These silver points were not ideal in that sometimes the seal at the root tip failed.  In addition, if the tooth needed work completed on its crown portion, any disturbance or bumping of the rigid silver points could disturb the seal at the root tip opening--causing the root canal to fail.  Thus, another beneficial quality of gutta percha is that the material can be touched, ground, melted out or cut off without the seal being broken because the material is not rigid.

The center photo to the left, shows the gutta percha point just sticking out the access opening on the tooth.

Root canal therapy is usually performed with the aid of a rubber dam.  The rubber dam isolates the individual tooth being worked on.  This prevents small instruments from being swallowed or inhaled into the lungs, but it also keep saliva and bacteria out of the canals.  In addition, the dam also protects the patient from some of the caustic chemical used to clean the root canal system.

In most cases, a root canaled tooth needs to have a crown placed on it when the root canal is finished.  The loss of a blood supply makes the endodontically treated tooth more brittle and susceptible to breakage.  The tooth dehydrates and becomes less flexible without a blood supply.  While these teeth can still take much pressure on them, they do not do well with shearing forces on them--which are typical when we chew.  The big opening at the top of the tooth further weakens it.  A crown put over the tooth is inflexible and so pressure exerted on the tooth will be distributed over the whole of the tooth, and not on a single spot which can cause breakage.  Crowns and root canals often go hand in hand.