Molecular analysis of oral microbial communities has indicated that the human mouth provides a habitat for approximately 700 species of bacteria.The oral cavity is somewhat unique, since it provides hard, nonshedding surfaces (teeth) that are accessible for microbial colonisation. Oral microorganisms live in biofilm. Biofilms are composed of microbial cells encased within a matrix of extracellular polymeric substance such as polysaccharides, proteins and nucleic acids. In a biofilm, bacteria have the capacity to communicate with each other by the process called quorum sensing.