Objective To study the inhibitory effects of the extracts of Periplaneta americana on the growth of Porphyromonas gingivalis in vitro. Methods Porphyromonas gingivalis ATCC33277 was chosen as the experimental
bacterium. The extracts of Periplaneta americana was double diluted to different concentrations by two-fold dilution, its effect on Porphyromonas gingivalis was measured by the minimal inhibitory mass concentration（MIMC）,
the minimal bactericidal mass concentration（MBMC） and D590 value of different culture medium at different times （0, 4, 8, 12, 24, 48 h）. Results The MIMC and MBMC of the extracts of Periplaneta americana was 2.5 g·L-1
and 5 g·L-1, respectively. The extracts of Periplaneta americana inhibitted multiplication of Porphyromonas gingivalis significantly and the effects became stronger with concentration increasing. Conclusion The antibacterial activity
of the extracts of Periplaneta americana on Porphyromonas gingivalis was significant, indicating that the extracts of Periplaneta americana can be used as an agent for prevention of periodontal disease.
