The purpose of this study was to prevent cross-contamination of dental hygienists by aerosols. We performed prophylactic scaling on 30 patients who visited the dental clinic. Microbiologic identification and SEM imaging were performed to confirm the number of microorganisms in the aerosol. Data analysis showed significant difference between two groups using SPSS (ver.21). According to the results, it was confirmed that Gram-positive and Gram-negative microorganisms were present in the aerosol, and these microorganisms were identified as microbes causing opportunistic infection in human body. In addition, chlorhexidine gargles were reduced to a significant level to reduce the number of microorganisms in the aerosol. A dental hygienist is likely to stay in a clinic room for a long time and be exposed to the generated aerosols. In order to prevent this, dental hygienists must thoroughly implement protection through personal protective equipment such as face shields and mask. In addition, reducing the number of microorganisms in the patient's mouth can be used gargling agents. In conclusion, the risks of cross-infection will be reduced through these methods.