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Daily oral hygiene could be "life-saving" amid the coronavirus outbreak, a scientist has said.
In February 2021, a Qatar University study suggested severe gum disease raises the risk of dying with the infection by nearly nine times.
A team of international scientists now believes a "breach in the immune defences of the mouth" enables coronavirus particles in saliva to enter the lungs via the bloodstream, potentially triggering complications.
With gingivitis making gums "leakier", the scientists recommend people take "simple but effective daily steps to maintain oral hygiene", like regularly brushing their teeth, using interdental sticks or even gargling with salt water.
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This comes after French researchers reported swilling with mouthwash that contains the antiseptic povidone iodine may reduce the number of coronavirus particles in a patient's nose and throat.
Most adults in the UK have gum disease to some extent, which tends to manifest as bleeding gums while brushing.
"Gum disease makes the gums leakier, allowing microorganisms to enter into the blood," said study author Professor Iain Chapple, from the University of Birmingham.
The coronavirus may then pass through the veins in the neck and chest to the heart, before being pumped into the lungs, the scientists wrote in the Journal of Oral Medicine and Dental Research.
"Simple measures – such as careful toothbrushing and interdental brushing to reduce plaque build-up, along with specific mouthwashes, or even saltwater rinsing to reduce gingival – could help decrease the virus' concentration in saliva," said Professor Chapple.
This may "mitigate the development of lung disease and reduce the risk of deterioration to severe COVID-19 [the disease caused by the coronavirus]", he added.
The oral health benefits of mouthwash has been debated, with some arguing the rinses remove any decay-fighting fluoride left behind by toothpaste.
The NHS therefore recommends people do not use mouthwash, even if it contains fluoride, immediately after brushing.
Early research suggests the coronavirus is mild in four out of five cases, however, certain characteristics raise a person's risk of complications, like old age and obesity.
Gum disease may explain why some seemingly healthy people occasionally become seriously ill with the infection, according to the international scientists.
"It could change the way we manage the virus – exploring cheap or even free treatments targeted at the mouth and, ultimately, saving lives," said Professor Chapple.
At-home treatments are limited, however, the asthma drug budesonide may be recommended on a case-by-case basis.
When it comes to oral therapies, the scientists have stressed further research is required.
Professor Ian Jones, from the University of Reading, has previously pointed out any benefit that comes with using mouthwash is temporary, adding "the constant replacement of the virus is the issue".
While further research is carried out, Professor Chapple said: "Daily oral hygiene and plaque control will not only improve oral health and wellbeing, but could also be lifesaving in the context of the pandemic."
Gum disease is caused by a build-up of plaque on the teeth, which can be prevented by brushing at least twice a day and flossing regularly. Dental check-ups also enable any hardened plaque to be removed.
In more severe cases, a dentist may recommend a specialist mouthwash. Deep cleans and even surgery are required in some incidences.
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Could mouthwash combat coronavirus?
In May 2020, scientists from Cardiff University called for research into whether mouthwashes available on the high street reduce the coronavirus' transmission.
Ingredients like ethanol and cetylpyridinium have been shown to disrupt the fatty membrane of pathogens like the coronavirus. Povidone iodine has also inactivated the virus in just 15 seconds in laboratory studies.
"In test tube experiments and limited clinical studies, some mouthwashes contain enough of known virucidal ingredients to effectively target lipids in similar viruses," Professor Valerie O’Donnell, from Cardiff University, has previously said.
The coronavirus is known to replicate in the salivary glands and throat, which mouthwashes reach.
The infection is also said to be "highly sensitive to agents that disrupt lipid bio-membranes". Other viruses from the same class, which can cause common colds or Severe acute respiratory syndrome (Sars), have been inactivated by "biocidal agents".
In 2017, a group of scientists found exposing a pathogen from the coronavirus class to 34% ethanol "completely prevented subsequent viral replication".
When it comes to povidone iodine specifically, Professor Stephen Challacombe, from King's College London, has previously said: "I have no doubt this should be used and had it been, it would have saved lives."
Some believe there is nothing to lose, with mouthwashes being inexpensive, readily available and relatively safe.
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