Host-parasite interface and preventive dentistry

Current understanding of the pathogenic etiology of supra- and subgingival plaque assumes dynamic changes of pathogenic potential depending upon the crosstalk among resident biofilm, as well as that among microbial communities and host tissues, called the ecological plaque hypothesis. Manipulation of bacterial and environmental factors, which affect the proportion and virulence potential, has potential for the control of the pathogenicity of biofilm. Most periodontal pathogens, except Actinobacillus actinomycetemcomitans, are oxygen-sensitive, proteolytic species and are thus unable to survive inside the plaque, which is sufficiently thin to allow oxygen exposure, and also lacks a nutritional supply of protein and some other essential factors. A preventive strategy against these pathogenic microbes would be an ecological approach to maintain health-compatible microflora on the surface of teeth. On the other hand, the strategy against A. acinomycetemcomitans, which is the microbe to which Koch's postulate is most applicable, would be employed in an approach to eliminate this pathogen from the microbial community by use of antibiotics or the humoral immune response of the host. For accomplishing both strategies, we discuss the host-parasite interface, not only the interaction but also the ecological and structural factors, for the purpose of preventing the onset and progression of periodontal diseases.