As the age increases, the oral cavity, that is, the teeth and periodontium, also begin to age, and accordingly, a preparation process is required. The preparation process is an important period for oral health management to start continuously with oral health education consisting of knowledge, attitude, and behavior from the 20s. Therefore, to design a clinical dental hygiene course for patients who visited a dental clinic in Gyeonggi-do and received continuous care in an oral health care room after treatment, we tried to analyze the data of the dental hygiene assessment. As a dental hygiene assessment tool, based on personal information and general medical history, dental visit experience, bleeding on probing(BOP), bad breath measurement, phase contrast microscopy, and O’Leary index were performed. The number of subjects who had dental visits was 75.4% and those without experience were 24.6%, and as a result of the periodontal examination, generally bleeding was found in 76.3%. In preventive oral care, the stage of dental hygiene assessment in the 20s is an important first step. From this point on, it is an important time to be systematically habituated so that you can take responsibility for your own oral condition. Therefore, in this study, the results of dental hygiene assessment through oral examinations of subjects in their 20s are derived and presented as basic data for the development of dental hygiene performance competency of dental hygienists during the clinical dental hygiene process in oral health education and oral health management.