Inhibitory and preventive effects of *Arnebia euchroma* (Royle) Johnst. root extract on *Streptococcus mutans* and dental caries in rats

BACKGROUND: Dental caries is a prevalent oral disease. Arnebia euchroma (Royle) Johnst. root (AR) extracts have anti-inflammatory, anticancer, and antibacterial properties. This study investigated the antibacterial impact of AR extract on Streptococcus mutans (S. mutans) UA159 and its anti-caries effect in rats. METHODS: Antibacterial activity against S. mutans planktonic cells and biofilms was assessed using bacterial and biofilm sensitivity tests and live–dead staining. Fluorescently tagged bacteria were used to evaluate adhesion to saliva-coated hydroxyapatite (HAP). In vivo anti-caries efficacy and safety were assessed in a rat caries model. RESULTS: AR extract inhibited S. mutans growth and biofilm formation, disrupted and reduced established biofilms, and inhibited bacterial adhesion to saliva-coated HAP. In a rat model, AR extract significantly reduced the incidence and severity of smooth-surface and pit-and-fissure caries while showing excellent biosafety. CONCLUSIONS: AR extract shows strong antibacterial activity against S. mutans and reduces dental caries in rats, suggesting Arnebia euchroma could be utilized for prevention and treatment of dental caries.