The inside of the tooth has a central area which is comprised of the nerve and blood supply that keeps the tooth nourished and healthy.
If the nerve is compromised due to trauma or decay, the nerve inside the tooth could begin to die. When the nerve dies the soft area becomes necrotic and can cause an infection that can become serious if not treated.
A patient could be treated by antibiotics to help control the infection temporarily, but a root canal is necessary to remove the infected and necrotic tissue. Without the root canal, the infection will return. The procedure time depends on the tooth and how many roots it has and may take two visits.