Oral microbial flora refers to the population of microorganisms that inhibit skin and mucous membrane of the oral cavity of the normal healthy persons. The microbial cells in the body outnumber the total number of cells in the human body by 10 folds. The mouth harbors a diverse, abundant and complex microbial community on varied surfaces of the oral cavity including both soft and hard tissues of the oral tissues as biofilms. Oral bacteria have evolved mechanisms to sense their environment and invade or modify the host. Bacteria occupy the ecological niche provided by both the tooth surfaces and gingival epithelium. The equilibrium is maintained by the innate host defense system constantly which monitors the bacterial colonization and prevents bacterial in invasion of local tissues. An understanding of the oral environment and microbial interactions leads to understanding the main causes for the onset of oral diseases. The present review highlights the role of microbial flora in health and oral diseases laying emphasis on its pathogenesis.
Key words: Human microbiome, Colonisation, Homeostasis, Adhesions, Anti-bacterial factors.