A root canal is the space within the root of a tooth. It is part of a naturally occurring space within a tooth that consists of the pulp chamber (within the coronal part of the tooth), the main canal(s), and more intricate anatomical branches that may connect the root canals to each other or to the surface of the root.
The bad news begins with the anatomy of our teeth. The enamel covers the chewing surfaces of our teeth and is generally what we see inside our mouths. This layer is very strong, yet only 1 1/2 to 2 millimeters thick at the most. This covers dentin, which comprises most of the tooth volume. A less strong, but dense, single cell layer, called cementum, covers the roots of teeth. The pulp chamber is within the body of the tooth.
Root canals presenting an oval cross-section are found in 50%-70% of root canals. In addition, canals with a "tear-shaped" cross section are common whenever a single root contains two canals (e.g., mesial roots of lower molars). Nevertheless, these aspects of root-canal anatomy are not seen or recognized in conventional 2D radiographs, as the long axis of their flat cross section is usually directed in parallel to the direction of the x-ray beam. With the increased use of Cone Beam Computerized Tomography (CBCT), these shapes are likely to be more and more often seen and recognized not only by endodontists but also in the clinical environment of general practice.
When tooth decay spreads and attacks a tooth, it can usually be removed by a dentist and the tooth saved with a filling. However, if the decay is neglected or not discovered until after it spreads into the root canal of the tooth itself, then the nerve and blood vessels become infected from the bacteria which are part of the tooth decay process.
The main pulp chamber, generally centered within the body of the tooth and root(s), is not the only tube within our teeth. In fact, there can be one or more “lateral accessory canals” running from the main chamber outward and through the cementum. In addition, there is also a highly specialized network of microscopic tubes (tubules), designed by our Creator to supply nutrients to the dentin as long as the tooth is alive. Each of these tubules begins at the surface of the pulp chamber and extends out to the enamel or cementum surface of the dentin.
In fact, most teeth with root canals can remain as a functioning component, especially if properly restored. It is not surprising that most dentists and their patients pursue this therapy when indicated. However, there is more than meets the eye regarding this subject.