The inhibition of eugenol on glucan is essential for the biofilm eradication effect on caries-related biofilm in an artificial mouth model.

This study aimed to evaluate the inhibitory effects of herbal extracts on caries-related bacteria, glucan and biofilm in vitro. Sensitive tests of bacteria were carried out by broth dilution method on a 96-microwell plate. Glucan inhibition tests were carried out using the phenol sulphate method. A minimum biofilm inhibitory concentration (MBIC) test was performed in an artificial mouth model. The results of the MBIC of agents were 8, 16 and 32 mg mL(-1) for eugenol, tannic acid and magnolol, respectively. For the results of glucan inhibition tests, over 63%, 28% and 27% inhibition occurred on insoluble glucan syntheses of Streptococcus sobrinus for eugenol, magnolol and tannic acid, respectively. Over 46%, 16% and 13% inhibition on soluble glucan syntheses for eugenol, magnolol and tannic acid, respectively, were also observed. In conclusion, the inhibition of eugenol on glucan is essential for the biofilm inhibition effect on caries-related biofilm in an artificial mouth model in vitro.