I understand the COVID-19 virus has a long incubation period during which carriers of the virus may not show symptoms and still be highly contagious. Given the current limits in virus testing, it is impossible to determine who has it and who does not have COVID-19.
Dental procedures create water spray (aerosols), which is one way the disease can be spread. The ultra-fine nature of the spray can linger in the air for several minutes to hours, which can transmit the COVID-19 virus.