The human mouth is a host of a large gamut of bacteria species, with over 700 of different bacteria strains identified. Most of these bacterial species are harmless, some are beneficial (such as probiotics assisting in food digestion), but some are responsible for various diseases, primarily tooth decay and gum diseases such as gingivitis and periodontitis. Dental plaque has a complicated structure that varies from patient to patient, but a common factor in most cases is the single species of bacterium acting as a secondary colonizer, namely Fusobacterium nucleatum, while the actual disease is caused by a variety of tertiary colonizers. We hypothesize that destruction of a compound biofilm containing Fusobacterium nucleatum will prevent tertiary colonizers (oral pathogens) from establishing a biofilm, and thus will protect the patient from developing gingivitis and periodontitis. In this paper, we report on the effects of exposure of compound biofilms of a primary colonizer Streptococcus gordonii combined with Fusobacterium nucleatum to iron oxide nanoparticles as possible bactericidal agent.