Nitrous oxide gas is the active drug used by dentists in inhalation sedation dentistry to offer comfortable and pain-free treatments and help their patients to overcome their dental fear and anxiety. Even if you do not have a dental phobia, use of nitrous oxide sedation can help increase your level of comfort during dental procedures and shorten treatment time. It is considered as the safest alternative to other types of dental sedation such as intravenous conscious sedation and general anesthesia.
The chemical formula of nitrous oxide is N2O, also called Dinitrogen Monoxide. It is one of the several oxides of nitrogen; the others most known are nitric oxide (NO) and nitrogen dioxide NO2.
The nitrous oxide molecule’s structure is a linear chain of two nitrogen atoms, with the second one bound to an oxygen atom.
At room temperature N2O is a colorless gas with a slightly sweet odor and taste. It can be produced by the reaction of diluted nitric acid with zinc, but the most common method is by heating carefully ammonium nitrate (NH4NO3) at 200o C which decomposes into N2O and water (H2O).
Nitrous oxide is considered an air-pollutant as it is one of the greenhouse gases. When N20 reacts with oxygen, it is oxidized to NO which reacts with ozone causing ozone depletion from the stratosphere zone of the atmosphere. It is estimated that nitrous oxide is by 6% responsible for the increase of temperature due to the greenhouse effect. The contribution of nitrous oxide used in dentistry to its overall emissions is extremely minimal, so you should not regret having nitrous oxide dental sedation even if you are environmentally sensitive.
Nitrous oxide has low solubility in blood, allowing it to diffuse rapidly across the alveolar-arterial membrane from the alveoli to the pulmonary circulation and reach the brain within a few seconds through the bloodstream. Although the exact ways that nitrous oxide gets its analgesic and anti-anxiety properties are not clear, several theories have been proposed.
It has been suggested that there are possibly multiple mechanisms of action that lead to the N2O effects. However, the most widely accepted theory is that the analgesic effect is linked to the interaction of nitrous oxide with the opioid receptors, which seems to alter the way that pain is processed by the brain, possibly similar to the way of action of morphine.
Nitrous oxide has been shown to interact with proteins in the nerve membrane, altering its structure, which leads to reduced flow of impulses through the Central Nervous System. The anxiolytic effect is achieved by its interaction with the GABA-A receptors which are inhibitory neurotransmitters, decreasing the activity of the nervous system. Nitrous oxide seems to depress almost all senses and sometimes memory.
As soon as the dentist interrupts the administration of the gas, nitrous oxide is excreted rapidly from the lungs and its effects are reversed, with full recovery achieved within a few minutes.
The symptoms you will feel when breathing the N2O/O2 mixture depend on the depth of the sedation level which is mainly controlled by the relative concentration of the nitrous oxide in the mixture. This could start from 30% and reach up to 70% (but no more to avoid the risk of hypoxia).
The initial feeling of nitrous oxide sedation is a lightheadedness and a tingling sensation, especially in the arms and legs, which is followed by a feeling of warmth all over the body.
As the sedation reaches the desired levels, you will experience a pleasant feeling of euphoria and/or floating and you will become completely relaxed. At the same time, your threshold of pain continues to rise. A feeling of numbness develops especially in the soft tissues of the mouth. This can allow for many common dental procedures to be performed without the need of additional local anesthesia.
At the proper level for dental sedation you will be able to breath on your own, maintain your body’s functions and respond to your dentist, while you feel no pain and you are fully relaxed.
If you start to feel sleepy, like dreaming, or have difficulty to keep your eyes open or speak, you are at the edge of being over-sedated and you move at a deeper sedation level than you should. Nausea is a clear sign of over-sedation. Nitrous oxide can induce loss of consciousness at high concentrations, close to 70% or higher. If you feel any of these symptoms you should notify your dentist in order to adjust lower the concentration of nitrous oxide.
After the treatment you will return to a normal state in a few minutes without any ‘hangover’ effect, and you will be able to drive home on your own. A mild amnesia is reported in some cases, with the patient not remembering all of what happened when sedated.