ABSTRACT Introduction: Periodontitis is defined as an inflammatory disease in the supporting tissues of teeth which is caused by microorganisms of certain groups. Objective: This study aims to know the inhibition power of bandotan leaf extract (Ageratum conyzoides L.) against the growth of bacteria causing periodontitis (Porphyromonasgingivalis). Method:The type of study used in this research is experimental laboratory. The design of this study used is post test only control group design used the method of dilution and disk-diffusion method. Results: The activities of bacteria can only be observed with the method of diffusion to see the inhibition zone. An extract of bandotan leaf (Ageratum conyzoides L.) with the concentration of 100% has the largest inhibition zone namely 16,25±0,66 mm and the inhibition zone is larger than control positive namely metrodinazole used as a comparison antibiotic from the extract of bandotan leaf (Ageratum conyzoides L.). This research has proven that the extract of bandotan leaf extract (Ageratum conyzoides L.) are effective as inhibitory properties against Porphyromonasgingivalis. Conclusion: The extract of bandotan leaf (Ageratum conyzoides L.) is effective as the inhibition power against Porphyromonasgingivalis. Keywords: Ageratum conyzoides L, PorphyromonasGingivalis, Periodontitis Correspondence: Harun Achmad Department of Pediatric Dentistry, Dentistry Faculty of Hasanuddin University Makassar, South Sulawesi, Indonesia E-mail: harunachmader@gmail.com DOI: 10.31838/srp.2020.4.58 @Advanced Scientific Research. All rights reserved