Long in the tooth: Oral bacterial communities and chronic periodontitis

Abstract

The oral cavity provides a fertile environment for the growth of microorganisms. It has a high and relatively constant temperature, high moisture level and is rich in nutrients. The range of hard and soft tissue surfaces provides a variety of distinctly different microhabitats. The unique, non-shedding hard surfaces of teeth in particular allow for accretion of the thick, complex, structured polymicrobial biofilms known as dental plaque. The majority of oral bacteria exist as components of these biofilms that confer benefit to the host by helping to prevent colonisation by exogenous, often pathogenic, microbes. Colonisation of the oral cavity by bacteria occurs soon after birth and a diverse commensal microbiota becomes established. Over 700 bacterial taxa inhabit the oral cavity making it one of the most bacterially biodiverse regions of the human body. This biodiversity exists despite the large number and variety of antimicrobial agents produced by the host in saliva, gingival crevice fluid and on epithelial surfaces, and the acquired immune response to particular bacterial species. There is a major division between the ecologies of supragingival and subgingival plaque found on the tooth surface above and below the gingival margin respectively.