The Etiology and Pathogenesis of Periodontitis Revisited

The science of periodontology has yielded significant insights into this common disease of man. The field of anaerobic microbiology is arguably developed to its current level by periodontal researchers and our treatment strategies are based on our understanding of the infectious nature of the disease. Yet, we are in the midst of a major paradigm shift in periodontology. We have come to understand that while the etiology of periodontitis is bacteria, the pathogenesis is inflammatory. Our understanding of regulation of inflammation in periodontitis is far from complete; however, as our understanding of periodontal inflammation increases, our current understanding of the microbiology of periodontitis becomes less clear. While we think we know that bacteria initiate the disease, the role of specific bacteria is still unknown. We cannot cultivate most of the bacteria associated with the disease and new data would suggest that we don’t really understand the relationship of the biofilm to inflammation. A review of the literature will reveal that our knowledge of the microbiology of periodontitis is based on large cross-sectional and association studies. Periodontitis is seen as the direct consequence of bacterial invasion and is regarded as an infectious disease. It is however, not possible to draw causeand-effect inferences from these studies; the implication of the “red complex” as pathogens is an “association”. New work in medicine and other studies in periodontology have introduced a new idea in biofilm biology. That is, the host inflammatory response dictates the composition of the biofilm . What this means is that the inflammatory response changes the microenvironment of the biofilm and selects for specific organisms. One might then argue that P.g. and T.f. overgrow in the periodontal GUEST EDITORIAL