Oral biofilms revisited: A novel host tissue of bacteriological origin.

The central theme of this volume of Periodontology 2000 is that the microbial dental plaque biofilm, specifically the subgingival dental plaque biofilm, mimics a human tissue in both structure and function. As a basis for this assertion we use the definition of a tissue as an aggregate of similar cells and cell products forming a defined structure with a specific function, in a multicellular organism. Accordingly, we propose that the dental plaque biofilm represents an acquired human tissue largely of bacterial origin that maintains the health of gingival tissue. Furthermore, we acknowledge that disease can be defined as a deviation from the normal structure or an interruption to the function of any body part, organ, or system, and that is manifested by a characteristic set of symptoms and signs whose etiology, pathology, and prognosis may be known or unknown. Therefore, in this volume we present the concept that periodontitis is a disruption of the normal function of the healthy subgingival plaque biofilm with concomitant disruption to its functional properties in relation to innate defense surveillance and tissue maintenance, leading to excessive, deregulated inflammation and tissue destruction.