evaluation of biofi lm removal activity of quercus infectoria galls against streptococcus mutans

background: dental caries is one of the most prevalent infectious diseases affecting humans of all ages. streptococcus mutans has an important role in the development of dental caries by acid production. the purpose of this study was to evaluate the antibacterial and biofi lm disinfective effects of the oak tree quercus infectoria galls against s. mutans. materials and methods: the bacterial strain used in this study was s. mutans (atcc: 35668). two kinds of galls, mazouj and ghalghaf were examined. galls were extracted by methanol, ethanol and acetone by soxhlet apparatus, separately. extracts were dissolved in sterile distilled water to a fi nal concentration of 10.00, 5.00, 2.50, 1.25, 0.63, 0.31, and 0.16 mg/ml. microdilution determined antibacterial activities. the biofi lm removal activities of the extracts were examined using crystal violet-stained microtiter plate method. one-way anova was used to compare biofi lm formation in the presence or absence of the extracts. results: the methanolic, ethanolic, and acetonic extracts of q. infectoria galls showed the strong inhibitory effects on s. mutans (p < 0.05). the minimum inhibitory concentration (mic) and minimal bactericidal concentration (mbc) values for the mazouj and ghalghaf gall extracts against s. mutans were identical. the mic values ranged from 160 μg/ml to 320 μg/ml, whereas the mbc values ranged from 320 μg/ml to 640 μg/ml. all extracts of q. infectoria galls signifi cantly (p < 0.05) reduced biofi lm biomass of s. mutans at the concentrations higher than 9.8 μg/ml. conclusion: three different extracts of q. infectoria galls were similar in their antibacterial activity against s. mutans. these extracts had the highest biofi lm removal activities at 312.5 μg/ml concentration. the galls of q. infectoria are potentially good sources of antibacterial and biofi lm disinfection agent. key words: biofi lm removal activity, dental plaque, oak gall, plant extracts, streptococcus mutans