Silver nanoclusters (AgNCs) are ultrasmall in size (< 2 nm) and are expected to be an effective antibacterial substance to combat oral infective diseases. In the present study, we synthesized AgNCs (Ag∼75) as the main component for esthetic and antibacterial application against the caries pathogen Streptococcus mutans. The results showed that AgNCs significantly reduced the turbidity and viability of S. mutans. In addition, the bactericidal effects of AgNCs were confirmed by LIVE/DEAD staining. After AgNC application to human dentin, no discoloration of dentin was observed, as compared to silver diamine fluoride application, and AgNC-treated dentin showed an inhibitory effect on colony formation by S. mutans. Therefore, AgNCs appear to be beneficial for dental therapy as an antibacterial and/or esthetic substrate
