Aim: this study investigated antibacterial properties of eighth generation bonding agent modified with 0.12% chitosan, 0.2% chitosan and 7% arginine against lactobacillus fermentum. Materials and Methods: 0.12% and 2% (w/w) of chitosan was added to adhesive. 7%(w/w) arginine was added to adhesive. Experimental adhesive was prepared in a dark room under controlled temperature and humidity. A sterile 10 wells were coated with 15μl of 8th generation bonding agent, its modifications with 0.12% chitosan, 0.2% chitosan & 7% arginine respectively for each group. Then 10μl bacterial suspension of lactobacilli was placed on bonding agent for 1hr at 37°C. Afterwards BHI broth (235μl) was added to each well and gently mixed for 2 min. Group 1 – control group Group 2 - 8 th generation bonding agent modified with 0.12% chitosan. Group 3 – 8 th generation bonding agent modified with 0.2% chitosan. Group 4 – 8 th generation bonding agent modified with 7% of arginine. After 48 hours bacterial growth was examined by turbidimetric analysis using spectrophotometer. Statistical analysis: One way Analysis of Variance (ANOVA) test was performed for intergroup comparison, followed by post hoc test.