Figure 4: Effect of kaurenoic acid (KA) on colony-forming units (CFU). Streptococcus mutans was inoculated into BHI broth with various concentration of KA and cultured for 24 h at 37°C. Inhibitory activity is shown in the presence of KA at concentrations ranging from 1 to 4 μg/mL. The CFU of S. mutans that adhered to 30 mg of saliva-coated hydroxyapatite beads that were treated with various concentration of KA are shown. When treated with 1–4 μg/mL KA, adherence was markedly repressed. Each value is expressed as a mean ± standard deviation. Significance was determined at when compared with the control. NaF was used as a positive control.