Extracting the nerve after it has been killed is usually not intensely painful, but there may be mild pain caused by residual pulp left behind. Nerve killing, also known as root canal therapy, is a surgical procedure to treat pulp necrosis and root infections, and can be performed by surgically removing the nerve or locally placing an inactivator to kill the nerve. After the nerve is killed, it loses its ability to respond to external stimuli such as pain, and therefore does not cause severe pain during subsequent operations. However, the nerve may remain unprocessed due to the fact that it may not be able to respond to external stimuli, such as pain. The nerve extraction process may cause slight pain due to the stimulation of the pulp, but it is within the acceptable range of the human body. If the sensation is severe, a local anesthetic may be appropriate. If pain occurs during the nerve extraction process, the doctor should be notified and pain medication should be used as directed by the doctor.