Dental patients and staff need to be protected from any potential infection by aerosol-generating procedures, the World Health Organization said on Tuesday, as dentists return to work in areas where the COVID-19 pandemic is easing.

There is currently no data on the spread of coronavirus from the dentist's chair, it said, calling for more research into common procedures that produce tiny floating particles that may cause infection if inhaled.

These include three-way air/water spray, ultrasonic cleaning equipment that removes deposits from the tooth surface, and polishing, the WHO said in new guidance.

"WHO guidance recommends in case of community transmission to give priority to urgent or emergency oral cases, to avoid or minimize procedures that may generate aerosol, prioritize a set of clinical interventions that are performed using an instrument and of course to delay routine non-essential oral health care," Benoit Varenne, a WHO dental officer, told a news briefing.

He added: "The likelihood of COVID-19 being transmitted through aerosol, micro-particles or airborne particles ... today I think is unknown, it's open to question at least. This means that more research is needed."

The WHO last month released general guidelines on the transmission of the coronavirus which acknowledged some reports of airborne transmission, but stopped short of confirming that the virus spreads through the air.

Dental facilities must have adequate ventilation to reduce the risk of the virus spreading in closed settings, it said on Tuesday.

"We think that the most pressing issue is related to the availability of essential personal protective equipment, PPE, for all health care personnel undertaking or assisting in the clinical procedures," Varenne said.