Periodontitis is a chronic
inflammation that develops due to a destructive tissue response to prolonged
inflammation and a disturbed homeostasis (
dysbiosis) in the interplay between the microorganisms of the dental biofilm and the host. The infectious nature of the microbes associated with
periodontitis is unclear, as is the role of specific bacterial species and
virulence factors that interfere with the host defense and tissue repair. This review highlights the impact of classical
virulence factors, such as
exotoxins,
endotoxins, fimbriae and
capsule, but also aims to emphasize the often-neglected cascade of metabolic products (e.g., those generated by anaerobic and proteolytic metabolism) that are produced by the bacterial phenotypes that survive and thrive in deep, inflamed
periodontal pockets. This metabolic activity of the microbes aggravates the inflammatory response from a low-grade physiologic (homeostatic)
inflammation (i.e.,
gingivitis) into more destructive or tissue remodeling processes in
periodontitis. That bacteria associated with
periodontitis are linked with a number of systemic diseases of importance in clinical medicine is highlighted and exemplified with
rheumatoid arthritis, The unclear significance of a number of potential "
virulence factors" that contribute to the pathogenicity of specific bacterial species in the complex biofilm-host interaction clinically is discussed in this review.