Nitrous oxide usage in sedation dentistry has already completed over 150 years of history in helping patients to withstand the pain and anxiety related with dental treatments. Nitrous oxide was the first sedative drug used in the history of sedation dentistry and it still remains the most popular and common method of dental sedation.
Two English scientists, Joseph Priestley and Sir Humphrey Davy, have made the major contribution in the history of nitrous oxide and anesthesia; Priestley for discovering the gas and Davy for identifying its potential use for anesthesia.
1772. The first step in nitrous oxide history was the discovery of N2O by Joseph Priestley (1733-1804) in 1772. Priestley an English cleric, political theorist, and physical scientist who is mostly remembered for the discovery of oxygen, achieved the isolation of a number of different gases. Priestly discovered nitrous oxide by heating ammonium nitrate mixed with iron filings, detoxifying the gas that was produced by passing it through water, and storing it as a gas which was first called ‘phlogisticated nitrous air’.
1775. Some years later, Priestley described how to produce nitrous oxide, which he then called ‘nitrous air diminished’, by heating iron filings dampened with nitric acid in his book ‘Experiments and Observations on Different Kinds of Air’ (1775).
1794. The first attempt of using nitrous oxide for medical reasons was made in 1794 by Thomas Beddoes who published a theory for treating tuberculosis and other lung diseases by inhaling of “Factitious Airs” (‘artificial gases’ such as N2O). In the same publication ‘Considerations on the Medical Use and on the Production of Factitious Airs’, the well known engineer James Watt presented two of his inventions, a machine for the production of gases like nitrous oxide, and a breathing apparatus for inhaling the gas.
1798. In 1798 Humphry Davy (1778-1829), a chemist and physicist who was working in producing several types of ‘artificial’ gases to be used in Thomas Beddoes’ clinic in Bristol, started to experiment on the effects of inhalation of new gases to patients. Humphry Davy was the first in the nitrous oxide history to observe its analgesic effect and its potential use for surgical operations, which were published in his book ‘Researches, Chemical and Philosophical’ (1800). Despite this important observation, for several decades afterwards the medical world ignored the Davy’s findings on the ability of nitrous oxide inhalation to decrease sensitivity to pain and its potential for anesthetic use during surgeries.
However, another of Davy’s findings became the center of interest and gained popularity. Davy had observed that patients who had inhaled nitrous oxide showed a state of euphoria, and sometimes erupted in laughter. Due to this amusing effect he proposed the use ‘laughing gas’ as an alternative name for nitrous oxide, and started to demonstrate the gas's exhilarating effect to gatherings of his friends. English society seemed to be very interested in these euphoria inducing properties of laughing gas. For the next few decades, nitrous oxide became very popular as a recreational drug, and it was common for British upper class to organize ‘laughing gas parties’ for amusement.
1844. Traveling lecturers started to make public demonstrations of the effects of nitrous oxide inhalation on audience volunteers. One of those performers touring the United States and Canada and making their living from administering nitrous oxide gas to spectators for entertainment was Samuel Colt the famous inventor of the Colt 45 revolver. It is said that these nitrous oxide demonstrations helped finance the prototype and production of Colt's first five-shot revolver. One of these public performances in 1844, organized by Gardner Colton in Hartford in Connecticut, was about to be the next important turn in the nitrous oxide sedation history. During the show, a man under the influence of nitrous oxide injured severely his foot, but he seemed to be unaware of the injury until the effect of the gas was gone.
This incident was noticed by a local dentist who happened to be in the audience, named Horace Wells (1815-1848), who realized that nitrous oxide must have had a painkilling effect. On the next day, Horace Wells arranged an experiment in his office. He inhaled 100% nitrous oxide and had one of his molar teeth that was infected extracted by one of his assistants. He noticed that while he was under the influence of the gas, he experienced no pain although he remained fully conscious. This was the first use of nitrous oxide as a dental anesthetic in the history of dentistry.
1845. Wells continued to use nitrous oxide gas for offering painless dental treatments to his patients thereafter. He also decided to promote this method to other dentists. Unfortunately his first official public demonstration for the dental society at the Harvard Medical School in Massachusetts General Hospital in 1845, failed when a patient proved unresponsive to the gas complaining of feeling slight discomfort, creating doubts about the efficacy of nitrous oxide as anesthetic. This misfortune lead to Wells loosing his professional reputation, and it was a significant setback in nitrous oxide usage in dentistry. He committed suicide three years later. However, to this day, Wells is recognized as the father of anesthesia. Since then, nitrous oxide has become one of the most popular and safe options for relieving pain and dental anxiety.
1863. Gardner Colton revived nitrous oxide use in dentistry in 1863, and by 1868 he claimed that he had treated 20,000 cases and extracted 75,000 teeth using N2O anesthesia.
1864. The American Dental Association finally recognized Wells as the discoverer of anesthesia in 1864 and the American Medical Association recognized the same in 1870. In the mean time, other agents were also introduced that provided conscious sedation and/or pain relief, or general anesthesia. The first general anesthetic drug was ether introduced in 1846, and chloroform followed a year later.
1868. Until 1868, dentists used 100% nitrous oxide which could not be used for prolonged cases and hypoxia cases were not uncommon. In 1868 Edmund Andrews, a Chicago surgeon, began to use nitrous oxide in combination with oxygen to provide a non-asphyxial form of anaesthetic, and as this method gained popularity, nitrous oxide and oxygen administered simultaneously, rapidly became the preferred anesthetic method in surgical as well as dental practices.
In hospitals, nitrous oxide was however found not to be a strong enough anesthetic for the use in large operations. Surgeons preferred the stronger ether and chloroform, it however became a common practice at hospitals to initiate all anesthetic treatments with a mild flow of nitrous oxide, and then gradually increase the anaesthesia with the stronger ether/chloroform.
1895. By 1895 there was enough literature available to support the continuous use of nitrous oxide and oxygen for prolonged dental cases, mainly based on the work of Herbert Paterson, and Clover and Coleman.
1950. During 1950s and 1960s, teaching of nitrous oxide inhalation sedation was introduced in US dental schools.
Today. Today, nitrous oxide is still widely used in both dentistry and medicine. It has proven to be a very safe and popular sedative agent and a mild anesthetic agent at higher concentrations. Administered properly, the nitrous oxide-oxygen technique has a very high success rate with a very small number of adverse effects and complications.