The tooth can be divided into three main layers for the purposes of this discussion. The top, or outer layer, is a hard, calcified surface called the enamel.

Directly beneath this layer, extending down into the gums and jawbone, is the dentin (sometimes called dentine).

The innermost layer is the pulp tissue. It is found most heavily concentrated in the crown of the tooth. At the center of the tooth, there is a cavity which houses this soft tissue, in an area sometimes referred to as the ?pulp chamber?.

Root canals are long passages full of the same soft pulp tissue, which are also found deep within the dentin of a tooth, and run from the pulp chamber through the roots of the tooth. These root canals extend deep into the gum and jawbone, connecting the pulp chamber to the nerves and tissue found in the jawbone.

Human teeth typically have between one and four root canals, with the greatest numbers found toward the back of the mouth. The tooth receives nutrition and sensory functions through the blood vessels and nerve tissue found running through these canals.

The tooth's nerve and pulp tissue is vital in the growth and development of the tooth. However, after the tooth has fully matured and ceases to grow, the nerves, blood vessels, and pulp tissue only provide sensory functions to the tooth.

If a cavity develops on the outer surface of the tooth, or if the tooth has undergone trauma from an accident, it may cause the soft tissue of the pulp chamber and root canals to become irritated, inflamed, or infected. If left untreated, the condition very well could develop into a serious, quite painful infection of the jaw and jawbone.

If a tooth appears likely to develop an infection such as this, a dentist may advise a pulpectomy, more commonly referred to as a root canal, or root canal treatment.

In a root canal treatment, or pulpectomy, the dentist will attempt to scrape out the pulp tissue from both the pulp chamber and the root canals themselves. The dentist will then fill the tooth and seal it, protecting it from any potential recurrence. While root canal procedures are commonly thought of as painful experiences, modern pulpectomies usually include the use of a local anesthetic to alleviate any pain that might be felt.