Since there are many ways of mouthwash and types of mouthwash products, they are often used in oral care and nursing situations without clear evidence of their use. It is very useful to select an appropriate mouthwash and to provide safe and efficient oral care in facilities and hospitals with limited time and human resources if it is possible to use the mouthwash not only according not only to the type of bacteria causing oral diseases but also to the stage of the disease. In this study, we report a comparison of the antibacterial, bactericidal, and ROS scavenging effects of Neostelin Green 0.2 ％ mouthwash solution® and sodium bicarbonate, which are clinically used as mouthwashes, against periodontal pathogens, caries-causing bacteria, and Candida. The direct scavenging effects of ROS, hydroxyl radicals（HO•）and superoxide（O2•－）, was measured by the electron spin resonance（ESR）method. Antimicrobial activity was estimated in reference to minimum inhibitory concentration（MIC）and minimum bactericidal concentration（MBC）using five bacteria, Candida albicans（C. albicans）, Streptococcus mutans（S. mutans）, Aggregatibacter actinomycetemcomitans（A. actinomycetemcomitans）, Porphyromonas gingivalis（P. gingivalis）, and Prevotella intermedia（P. intermedia）. HO• scavenging effects of Neostelin were significantly lower than those of sodium bicarbonate. O2•－ scavenging effects were significantly higher in Neostelin compared to sodium bicarbonate. For Neostelin, the antimicrobial and fungicidal effects to both species were confirmed to be sufficient within the range of concentrations indicated for pharmaceutical use. Although sodium bicarbonate showed high concentrations of MBC against S. mutans and P. gingivalis, while MIC was 2 w/v％, a concentration usually applied in clinical practice. MBC and MIC against A. actinomycetemcomitans and P. intermedia were both less than 2 w/v％；MBC against C. albicans was not effective unless the concentration of sodium bicarbonate was high（10 w/v％）. In this study, the differences in antioxidant and antibacterial effects were confirmed between Neostelin and sodium bicarbonate. Therefore, the present results could contribute to the clinical practice of oral care in the near future.
