Fig. 4

Combined effect of cinnamon water extract (2.5 mg/ml) and nicotine on S. mutans biofilm growth. Asterisks indicate significant differences (p < 0.05) with cinnamon water extract compared to samples without cinnamon water extract. The # symbol indicates significant differences (p < 0.05) between S. mutans biofilm growth with cinnamon water extract at different nicotine concentrations and the zero-nicotine concentration with cinnamon water extract. The @ symbol indicates significant differences (p < 0.05) between S. mutans biofilm growth without cinnamon water extract at different nicotine concentrations and the zero-nicotine concentration without cinnamon water extract