This study aimed to conceptualize the dental hygiene intervention performed by dental hygienists based on the dental hygiene process of care. The dental hygiene intervention classification was conducted on the qualitative content analysis method. The contents of the primary dental hygiene intervention classification were refined after review by three internal experts. The final classification of dental hygiene interventions was derived through an expert Delphi survey conducted twice with 15 professors in charge of clinical dental hygiene. In the Delphi survey, the content validity and clarity were evaluated. As a result of the first and second expert Delphi surveys, the content validity ratio for all dental hygiene interventions and definitions was ≥0.60, and the content validity index was ≥0.80. The degree of agreement was a minimum of 0.80 and a maximum of 1.00. Thirty-eight dental hygiene interventions were conceptualized, and the essence of the dental hygienist was confirmed. Dental hygienists are oral health experts who help in preventing oral diseases and promoting oral health by providing evidence-based comprehensive preventive management through interaction with their clients, and they are a primary care worker who could contribute to health promotion. In the future, dental hygienists are expected to be actively involved in the primary care system and dental clinical sites and contribute to health promotion through practical discussions for this purpose.