Last month, the World Health Organization recommended delaying “routine nonessential oral health care … until there has been a sufficient reduction in COVID-19 transmission rates from community transmission to cluster cases.”

The WHO was responding in part to the growing body of scientific evidence indicating novel coronavirus can be spread by respiratory droplets smaller than five microns in diameter known as droplet nuclei or, in more general terms, aerosols.

That’s concerning because aerosol-generating procedures are common in the dental workspace. According to the Centers for Disease Control, “Commonly used dental equipment known to create aerosols and airborne contamination include ultrasonic scaler, high-speed dental handpiece, air/water syringe, air polishing, and air abrasion.”

In a study published in May on the National Institutes of Health website and conducted by the School of Medicine at China’s Zhejiang University, “Possible aerosol transmission of COVID-19 and special precautions in dentistry,” researchers cited data demonstrating that aerosol generating procedures can transmit pathogens.

“When combined with bodily fluids in the oral cavity, such as blood and saliva, bioaerosols are created,” the study states. “These bioaerosols are commonly contaminated with bacteria, fungi, and viruses, and have the potential to float in the air for a considerable amount of time and be inhaled by the dentists or other patients.”

The study noted that so far, there have been “no reported cases of COVID-19 transmission in the dental setting.”

Image source: National Institutes of Health/Zhejiang University

In the United States, that’s in part due to interim guidelines issued by the American Dental Association and the CDC that urged for the reduction of aerosol-generating procedures and initially called for delaying nonessential dental care, just as the WHO did last month.

But the ADA was quick to “respectfully yet strongly disagree” with the WHO’s call to delay “routine” care now, as many dental offices have successfully reopened.

"Millions of patients have safely visited their dentists in the past few months for the full range of dental services," ADA President Chad P. Gehani said the day after the WHO’s announcement. "With appropriate PPE, dental care should continue to be delivered during global pandemics or other disaster situations."

The WHO, ADA and CDC are more often in agreement than not when it comes to oral healthcare and COVID-19. The ADA and CDC have cautioned against using aerosol-generating procedures since May and are in a sense ahead of the curve.

“Current data do not support long range aerosol transmission of SARS-CoV-2, such as seen with measles or tuberculosis,” the CDC states. On the other hand, “Short-range inhalation of aerosols is a possibility for COVID-19, as with many respiratory pathogens.”

That’s especially true in the close confines of the oral healthcare setting, where many of the primary tools used generate bioaerosols. Indicative of the situation’s urgency, both the ADA and the CDC advise avoiding all aerosol generating procedures if possible, during the pandemic.

“Avoid aerosol generating procedures whenever possible, including the use of high-speed dental handpieces, air/water syringe, and ultrasonic scalers,” the CDC’s current guidelines state. “Prioritize minimally invasive/atraumatic restorative techniques (hand instruments only).”

If aerosol generating procedures can’t be avoided, the CDC recommends using “four-handed dentistry, high evacuation suction and dental dams to minimize droplet spatter and aerosols.”

As more evidence of COVID-19’s airborne potential has come in, the CDC has modified the interim guidelines. In late August, it issued new personal protection equipment recommendations for dental healthcare personnel in areas with no to minimal community transmission and areas with moderate to substantial community transmission.

Dental healthcare workers in areas with no to minimal community transmission are now advised to “wear a surgical mask, eye protection (goggles or a face shield that covers the front and sides of the face), a gown or protective clothing, and gloves during procedures likely to generate splashing or spattering of blood or other body fluids. Protective eyewear (e.g., safety glasses, trauma glasses) with gaps between glasses and the face likely do not protect eyes from all splashes and sprays.”

Dental healthcare workers in areas of moderate to substantial community transmission are advised to take further precautions, especially if they’re performing aerosol generating procedures.

“During aerosol generating procedures DHCP should use an N95 respirator or a respirator that offers an equivalent or higher level of protection such as disposable filtering facepiece respirators, powered air-purifying respirators, or elastomeric respirators,” the new guidelines state.

The recommendation to wear an N95 respirator, its equivalent or better also applies to dental healthcare workers working with patients suspected or confirmed to have COVID-19.

“Airborne transmission from person-to-person over long distances is unlikely,” the new CDC regulations state. “However, COVID-19 is a new disease, and we are still learning about how the virus spreads and the severity of illness it causes. The virus has been shown to persist in aerosols for hours, and on some surfaces for days under laboratory conditions. SARS-CoV-2 can be spread by people who are not showing symptoms.”

Sometimes those people are patients, and both the CDC and the ADA advise dentists to check their patients for fever and other possible COVID-19 symptoms at the office door. Patients should be encouraged (but not forced) to wear at least a cloth mask to prevent spread of the virus. The CDC even recommends testing patients for coronavirus if quick test results are available.