The natural cavity
in the middle of a tooth is called the root canal. Inside that cavity is a soft area known as the pulp chamber. Within the root canal is also the nerve. Sometimes, the pulp inside the tooth becomes infected. If the problem is not treated, it can lead to a very serious infection.
If the pulp is not eradicated from the root canal, the potential for abscess is great. When you have an abscessed tooth, the swelling can spread. It may even extend to other parts of your face. Your neck and head can become swollen, too.