SARS-CoV-2, the virus behind Covid-19, spreads mainly through respiratory droplets, and dental procedures are known to produce an abundance of aerosols -- leading to fears that flying saliva during a cleaning or a restorative procedure could make the dentist's chair a high-transmission location.

Researchers from the Ohio State University in the US, set out to determine whether saliva is the main source of the spray, collecting samples from personnel, equipment and other surfaces reached by aerosols during a range of dental procedures.

Among the 28 patients enrolled for the study, salivary bacteria were detected in condensate from only eight cases and of those, five patients had not used a pre-procedural mouth rinse. The SARS-CoV-2 virus was identified in the saliva of 19 patients, but was undetectable in aerosols in any of the cases.

Microbes from irrigants contributed to about 78 per cent of the organisms in aerosols while saliva, if present, accounted for 0.1 per cent to 1.2 per cent of the microbes distributed around the room.

By analysing the genetic makeup of the organisms detected in those samples, the researchers determined that watery solution from irrigation tools, not saliva, was the main source of any bacteria or viruses present in the spatter and spurts from patients' mouths.

Even when low levels of the SARS-CoV-2 virus were detected in the saliva of asymptomatic patients, the aerosols generated during their procedures showed no signs of the coronavirus. In essence, from a microbial standpoint, the contents of the spray mirrored what was in the office environment. The study was published in the Journal of Dental Research.

"Getting your teeth cleaned does not increase your risk for Covid-19 infection any more than drinking a glass of water from the dentist's office does," said lead author Purnima Kumar, Professor of periodontology at Ohio State.

"Hopefully this will set their mind at rest because when you do procedures, it is the water from the ultrasonic equipment that's causing bacteria to be there. It's not saliva. So the risk of spreading infection is not high," she said. "However, we should not lose sight of the fact that this virus spreads through aerosol, and speaking, coughing or sneezing in the dental office can still carry a high risk of disease transmission," Kumar said.