Background: Dentures as a prosthesis to overcome tooth loss have several components, one of which is the denture base. Denture bases can be made of both metallic or non-metallic materials such as heat cured acrylic resin. Heat cured acrylic resin has a drawback, namely the occurrence of porosity. As a result of porosity, the acrylic resin plate become a place for bacterial accumulation that it will cause denture stomatitis. Denture cleaning needs to be done so that the health of the oral cavity is maintained. Therefore, the use of herbal ingredients as an alternative to denture cleaning materials continues to be developed. Lime (Citrus aurantifolia) contains alkaloids, flavonoids, steroids, phenols, and tannins that have antibacterial effects. Objective: To analyze the effect of lime (Citrus aurantifolia) fruit extract concentration on immersion of heat cured acrylic resin on Streptococcus mutans. Materials and Methods: This type of study was a laboratory experimental with post test only control group design. There were 32 samples of heat cured resin acrylic with the size of each sample 10x10x2 mm3 which were divided into 2 groups, first group was 40% lime fruit extract and the second group was sterile aquades. Results: Immersion of heat cured acrylic resin denture base soaked with 40% lime fruit extract showed a significant difference in the number of colonies compared to sterile aquades (p<0,05). Conclusion: Soaking a heat cured acrylic resin plate on a 40% lime fruit extract can have an effect on Streptococcus mutans.