Majalah Kedokteran Gigi Indonesia Vol 9 No 1 – April 2023 ISSN 2460-0164 (print), ISSN 2442-2576 (online) Available online at https://jurnal.ugm.ac.id/mkgi DOI: http://doi.org/10.22146/majkedgiind.78246 7 RESEARCH ARTICLE Antibioflm activity of Cyanobacteria spirulina as an irrigation solution against Enterococcus faecalis Diana Soesilo*, Fani Pangabdian*, Eriza Juniar** *Department of Conservative Dentistry, Universitas Hang Tuah, Surabaya, East Java, Indonesia **Department of Pediatric Dentistry, Universitas Hang Tuah, Surabaya, East Java, Indonesia *Jl Arif Rahman Hakim 150, Surabaya, East Java, Indonesia;  correspondence: diana.soesilo@hangtuah.ac.id Submitted: 7 th October 2022; Revised: 30 th December 2022; Accepted: 9 th March 2023 ABSTRACT Sodium hypochlorite (NaOCl) is currently the golden standard for root canal irrigation. NaOCl at a concentration of 5.25% to 6% can eliminate E. faecalis, but this concentration can increase the risk of toxic efects. Cyanobacteria spirulina is known to produce several secondary metabolites that have antimicrobial activity against gram-positive and gram-negative bacteria. The aim of this study was to determine the antibioflm power of Cyanobacteria spirulina against the bioflms of Enterococcus faecalis at concentrations of 60 mg/ml, 70 mg/ml, 80 mg/ml, and 90 mg/ml. This research was a true experiment with a post-test only group design. The object of the research was divided into 6 groups. Group 1 was a negative control group, group 2 was a positive control group with 5% NaOCl, group 3, 4, 5, 6 were treatment groups given Cyanobacteria spirulina solution at a concentration of 60 mg/ml, 70 mg/ml, 80 mg/ml, and 90 mg/ml, respectively. Optical density (OD) of bacteria was bound by staining and analyzed by ELISA auto reader with a wave length of 595 nm (OD 595 nm). The results of the LSD test showed that the signifcance between K+ and P1, P2, P3 (p < 0.005), K+ and P4 (p=0.129), P1 and P2 (p=0.449), P3 and P4 (p=0.178). Signifcance of p < 0.005 showed a signifcant diference between the groups. The data were analyzed using the one-way ANOVA test followed by a double comparison test with the Least Signifcance Diferent (LSD) Post Hoc test method. Cyanobacteria spirulina solution at a concentration of 90 mg/ml had the greatest inhibitory efect on the bioflm formation of Enterococcus faecalis. Keywords: bioflm; Cyanobacteria spirulina; Enterococcus faecalis; irrigation solution; sodium hypochlorite INTRODUCTION Pulp and periapical infection are one of the tooth diseases of which the main cause is combination of aerobic and anaerobic bacteria. 1 Enterococcus faecalis is a facultative anaerobic gram-positive bacterium that is often found in about 80-90% of teeth with failed root canal treatment. 2,3 E. faecalis is resistant to several antibiotics and has the ability to cause a single infection / mono-infection. 4,5 Bioflm of the bioflm provides an optimal environment for the growth of microorganisms and facilitates the transmission of cellular genetic elements between bacteria. Bioflms play an important role in bacterial virulence because bioflms protect bacteria, especially uro-pathogens, against the antibacterial activity of antibiotics. This bacterial defense mechanism is formed due to changes in the characteristics of bacterial cells in environmental adaptation, such as inhibition of bacterial growth or in dormant metabolic conditions, which can increase resistance and tolerance to antibiotics. 6 Elimination of bacteria in root canals can be done by root canal treatment. Root canal irrigation is one of the stages that afects the success of bacterial elimination in root canal treatment. 7 Irrigation material is good if it is antimicrobial as well as has the ability to dissolve organic and inorganic tissues and has a low toxicity efect. 8 Sodium hypochlorite (NaOCl) is currently the golden standard for root canal irrigation. NaOCl at concentrations of 5.25% to 6% can kill E. faecalis, but these concentrations can increase the risk of toxic efects. 7 The disadvantages of NaOCl are that it is only efective for cleaning organic debris components, is toxic to periapical tissue, can