ABSTRACT
       Background and Objective: Anaerobic bacteria are the main cause of periodontitis. It has been shown that green tea and black tea have antibacterial effect. The aim of this study was to determine he antibacterial effect of Iranian green tea and black tea against Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia.
        Methods: Aqueous and methanolic extracts of Iranian green tea and black tea at concentrations ranging from 10 to 500 mg/ml were tested against standard strains of A. actinomycetemcomitans  (ATCC 33384), P. gingivalis (ATCC 33227) and P. intermedia (ATCC 25671) using agar disk diffusion, broth microdilution and determination of minimum inhibitory concentration.
         Results: P. gingivalis, A. actinomycetemcomitans and P. intermedia were sensitive to the methanolic extract of Iranian green tea at concentrations of 100-500 mg/ml, 10-500 mg/ml and 50-500mg/ml, respectively. P. gingivalis, A. actinomycetemcomitans and P. intermedia were sensitive to the methanolic extract of Iranian black tea at concentrations of 200-500 mg/ml, 20-500 mg/ml and 200-500 mg/ml, respectively. In addition, P. gingivalis, A. actinomycetemcomitans and P. intermedia were sensitive to the aquatic extract of Iranian green tea at concentrations of 200-500mg/ml, 100-500 mg/ml and 200-500 mg/ml, respectively.
        Conclusion: The aquatic and alcoholic extracts of Iranian green tea and black tea have antibacterial activity against A. actinomycetemcomitans, P. intermedia and P. gingivalis. Therefore, incorporation of Iranian black tea as an effective native herb could be beneficial for prevention of oral cavity diseases.
          Keywords: Tea, Green Tea, Antibacterial Agents, Anaerobic Bacteria.