I've been wondering about this, because of all the aerosols generated by dental instruments. Slate has the story:
Reopened offices will need a sanitation upgrade. Until COVID-19, practices followed protocols that are largely designed to stop the spread of bloodborne illnesses, because they were developed during the HIV/AIDS epidemic in the 1980s. But the way certain dental procedures can make saliva into aerosols makes dentists’ offices a prime environment for dispersing an airborne pathogen like the coronavirus. The coronavirus often infects people via saliva droplets; many dental instruments spray saliva, and the diseased particles can remain suspended in a mist for hours. Fillings, root canals, and other procedures that involve the use of drills and ultrasonic scalers, a cleaning tool that clears away tartar and plaque by vibrating, tend to produce aerosols. Teeth polishing can also result in saliva spray.
Here is how your appointment might go, from the moment you sit in the chair. You’ll likely have two people working on you at a time—a technique known as “four-handed dentistry”—in order to speed up the procedures and control the amount of spit that gets into the air. You may see a high-evacuation suction device, which looks a bit like a vacuum cleaner, near your face; it will draw in air from the general vicinity and remove infectious material. “It has an extension that we put right in front of the patient,” says Melisande Wolff, a dentist in West Palm Beach, Florida, who reopened her practice on May 4. “Any extra aerosol that gets past the suction devices that my assistant is already using will get picked up by that.” You also might spot HEPA air purifiers, which use a very fine mesh to catch particles.
Your dentist might have you wear a rubber dam over the bottom half of your face...