To understand how a root canal works, we need to have a basic understanding of the anatomy of the tooth. A tooth is hollow, like our bones, and is composed of several layers.
The outermost layer (above the gum-line) is called the enamel. Enamel is the hardest and most mineralized substance in the body. Beneath the gum-line, a substance called cementum covers the tooth roots. Under the enamel and cementum is the dentin. The dentin is about as hard as bone, and, unlike the enamel, dentin contains nerve endings. Beneath the dentin is the dental pulp.
The pulp is a vascular tissue, composed of capillaries, larger blood vessels, connective tissue, nerve fibers, and cells including odontoblasts, fibroblasts, macrophages, and lymphocytes. The pulp is needed to nourish the tooth during its growth and development. After a tooth is fully mature, the only function of the pulp is to let us know if it is damaged or infected by transmitting pain.
How does the pulp become infected?
The most common way for the pulp to become infected is from an untreated cavity. A cavity is formed by acid in a rather unexpected way. Inside everyone’s mouth is a legion of bacteria – they are completely normal and there is nothing you can do about them. Some of these bacteria metabolize (eat) carbohydrate-containing foods or beverages and make acid as a by-product. The acid is strong enough to eat through the enamel and dentin. If left untreated, it will eventually expose the underlying pulp to bacteria inside our mouths and it gets infected. The pulp can also get infected from trauma to the tooth.
A blow to a tooth can cut off the blood supply to the tooth from our jawbone, and cause the pulp tissue to slowly die. Interestingly, a tooth that breaks within the enamel and dentin during trauma is less likely to need a root canal in the future because the fracture may absorb the trauma, sparing blood flow to the tooth. A third way a tooth can become infected is if there is long standing periodontal (gum) disease around the tooth. Bacteria from the infected gums can enter the tooth through small openings on the root surface (accessory canals) and cause a retrograde infection. Whatever way the tooth becomes infected, the pulp eventually dies, and over time, will cause a painful dental abscess within the surrounding jawbone.
How will I know if I have an infected tooth?
A tooth that becomes sensitive to hot or cold food or beverages or hurts when biting down may indicate an infected tooth. A tooth that becomes discolored or that causes the gums to swell around a tooth may also indicate a dental infection. In some cases, a tooth will have no symptoms, but a dental exam and x-ray will reveal a tooth that requires a root canal.
If the tooth is infected, why can’t I use an antibiotic to treat it?
If a tooth has an infection of the pulp, the only options are root canal therapy or extraction. As the pulp dies, the hollow tooth becomes a reservoir for bacteria to hide from the body’s immune system and any drugs that could fight the infection. In some cases, a dentist will prescribe antibiotics during or after treatment.