Nitrous oxide is a colorless, odorless combination of two gases—oxygen and nitrogen—that's used for its calming effect. The nitrogen-oxygen mixture is combined with additional oxygen then administered through a small, soft plastic mask that fits over your nose. Breathing in normally through your nose, you'll soon notice that you're feeling calm, relaxed, and disconnected from what's going on around you. Eventually, you'll reach what's called "conscious sedation," in which you are completely relaxed but can still respond to questions or requests from the dental care team. During conscious sedation, you also have a decreased perception of discomfort and a greater tolerance for lengthy dental procedures, even though nitrous doesn't make any part of your mouth numb.
You won't be asleep, and your natural reflexes will be completely intact, but you'll be profoundly relaxed, and the procedure will seem to go by very quickly. Once your treatment has concluded, you'll breathe pure oxygen for a few minutes to flush the nitrous oxide from your system.