An abscessed (infected) tooth is caused by tooth decay. When the pulp is diseased or injured and can’t repair itself, it dies. The most common cause of pulp death is a cracked tooth or a deep cavity. Both of these problems can let bacteria enter the pulp. Left without treatment, pus builds up at the root tip, in the jawbone, forming a “pus-pocket” called an abscess. An abscess can cause damage to the bone around the teeth. When the infected pulp is not removed, pain and swelling can result. Certain byproducts of the infection can injure your jaw bones. Without treatment, your tooth may have to be removed.
Today, with a special dental procedure called a root canal therapy, that tooth can be saved! The pulp is the soft tissue that contains nerves, blood vessels and connective tissue. It lies within the tooth and extends from the crown of the tooth to the tip of the root in the bone of the jaws. When the pulp is diseased or injured, the pulp tissue dies. A root canal treatment entails removing the diseased pulp, cleaning the canals, and sealing them off to protect them from future infiltration of bacteria. A crown is placed over the tooth as the final step to help make it stronger. Most of the time, a root canal is a relatively simple procedure with little or no discomfort involving one to three visits. Best of all, it can save your tooth and your smile!
This information was taken from the ADA.