Objectives The aim of the study was to investigate patients with coronavirus disease 2019 (COVID‐19) who visited dental clinics for treatment and to analyse the occurrence of additional COVID‐19‐confirmed cases according to the type of dental treatment and use of personal protective equipment (PPE). Methods Interviews were conducted in November 2021 via telephone, and written questionnaires were administered to dental hygienists working at the 24 dental clinics selected for the study, visited by patients with COVID‐19. The survey focused on the visit date, the treatment received, whether or not the dental personnel wore PPE while treating the patient, and how the dental clinic and the public health centre with jurisdiction over the clinic responded after the patient's visit. Results Additional confirmed cases occurred in two of the 24 dental clinics included. In both cases, scaling was performed, dental personnel did not use a face shield, and patients with COVID‐19 were asymptomatic. In 14 of the 22 dental clinics where additional confirmed cases did not occur, the dental personnel did not use face shields, and in 10 clinics, the dental personnel wore dental masks but not a KF94 mask. Based on these findings, which were obtained before the advent of the omicron variant, COVID‐19 cross‐infection did not appear to be high in dental clinics. Conclusion The rate of COVID‐19 cross‐infection before the advent of the omicron variant appeared to be low in dental clinics in Korea. Therefore, patients have no reason to delay necessary dental treatment if dental personnel put effort into wearing PPE.