Anesthesia is administered prior to a procedure to help dull pain or sedate a patient. The most common form is local anesthesia, meaning that it dulls pain in all or part of the mouth during dental work, but does not cause the patient to go to sleep. It usually wears off two to three hours after the procedure and is most often used when a patient is getting a filling or a root canal. Some people may require conscious sedation. Nitrous oxide or laughing gas is often used, as are oral sedatives and oral injections. The doctor will always discuss anesthetic and sedative options prior to administering them.