Underneath your tooth's outer enamel and within the dentin is an area of soft tissue called the pulp with blood vessels and nerves. Root canals are very small; thin divisions that branch off from the top pulp chamber down to the tip of the root. Teeth can have from one to four root canals.When the pulp becomes infected due to a deep cavity or fractures that allows bacteria to seep in, or injury due to trauma, it can die. Damaged or dead pulp causes increased blood flow and cellular activity, and pressure cannot be relieved from inside the tooth.

Pain in the tooth is commonly felt when biting down, chewing on it and applying hot or cold foods and drinks. Without treatment, the infection will spread, bone around the tooth will begin to degenerate. The only alternative is usually extraction of the tooth, which can cause surrounding teeth to shift crookedly, resulting in a bad bite. Though an extraction is cheaper, the space left behind will require an implant or a bridge, which can be more expensive than root canal therapy. Once filled, the area is permanently sealed. Finally, a porcelain crown is normally placed over the tooth to strengthen its structure and improve appearance.