Nitrous oxide (laughing gas) is an extremely helpful adjunct for dental treatment of the fearful patient. It was first discovered by Joseph Priestley in 1772, however, it was not until 1844 when Horace Wells used it as a medical anesthetic. Today, nitrous oxide is used in conjunction with local anesthetic when performing dental treatment on apprehensive patients. Nitrous oxide on its own cannot reliably anesthetize a patient profoundly enough for a patient not to feel a thing. Therefore, it must be used with novocaine to numb the area. Nitrous oxide is administered with pure oxygen and is breathed through a nasal hood. The machine that delivers the gas is a fail-safe machine which will turn off if the oxygen level falls below 35%. Nitrous oxide is not meant to put one to sleep, but merely relax. When given before the anesthetic injection, it can make that part of the procedure much more comfortable. It will put a patient in a state of mild euphoria and will alter the perception of sights, sounds, and time. It also has a mild amnesic effect leaving much less memory of the procedure. Another extremely nice feature of nitrous oxide is that the patient can be flushed with pure oxygen after the procedure and be totally lucid and able to drive home. Nitrous oxide can make a dental appointment a very pleasant experience.