In general, periodontal destruction results from imbalances in an individual's innate and acquired immune responses to their oral microbiota. A multifactorial risk pattern of periodontitis is recognized, including bacterial challenge, smoking, age, diabetes, and socioeconomic and genetic factors. In the initial phase pathogenic microbiota rather than single periodontal pathogens seem to play an important role. Despite the improvement of microbiological detection methods the actual bacterial dimension and their mutual relationships in an oral ecosystem is still unclear. At present no definite answer can be given to the question of whether the expression of either aggressive etiological agents (implying infection with a highly virulent microbiota), or a high level of individual susceptibility to periodontal disease, or a specific combination of both is the conducive factor in the etiopathogenesis of aggressive periodontitis.
The purpose of the current research was to analyze the prevalence of periodontitis-associated microorganisms in patients with generalized aggressive periodontitis and periodontally healthy elders using molecular-biologic detection methods like eubacterial PCR-amplification in combination with dot-blot hybridization. The oligonucleotide probes for the detection of periodontitis-associated bacteria Tannerella forsythensis, Porphyromonas gingivalis, Fusobacterium nucleatum, Fusobacterium spp., Campylobacter rectus, Actinobacillus actinomycetemcomitans, Prevotella intermedia, Eikenella corrodens, Veillonella parvula and Capnocytophaga ochracea were designed and evaluated. The results of the epidemiological study revealed frequent colonization by T. forsythensis, P. gingivalis, F. nucleatum and C. rectus in patients with aggressive periodontitis, however, individual variations were obvious. These microorganisms could predominantly be identified in periodontal pockets, but were significantly less common in healthy sites and in the elderly subjects. The putative pathogens T. forsythensis, P. gingivalis, F. nucleatum and C. rectus can hence be suggested as the key-bacteria in patients with aggressive periodontitis. A. actinomycetemcomitans could be detected in only a few patients, reducing its suspected importance in the etiopathogenesis of generalized aggressive periodontitis. Only a weak association for P. intermedia and E. corrodens with aggressive periodontitis or periodontal health could be seen. The results support earlier findings that generalized aggressive periodontitis is associated with a complex microbiota.
It is still controversial whether the presence of putative pathogens in periodontal sites without clinical disease increases the risk for future periodontal breakdown. The periodontitis-associated microorganisms are part of the indigenous oral microflora. In certain circumstances they are induced by environmental and host genetic factors to increase in proportions and unfold their virulent nature. The frequently observed co-infection of T. forsythensis and P. gingivalis or T. forsythensis and C. rectus in patients with aggressive periodontitis can implicate constellations of species which have the synergistic effect of enhanced virulence. Microbiological detection tests for putative periodontal pathogens are not of themselves diagnostic for periodontal disease, as periodontitis is a consequence of an opportunistic infection caused by microorganisms belonging to the resident microflora. Obviously, the influence of host immunity factors modifies the clinical outcome to a high extent. Patients with an altered inflammatory response may be less capable of tolerating the presence of specific organisms. Individuals with apparently low risk of developing destructive periodontal disease may have established a protective, so-called beneficial subgingival flora. In the present research C. ochracea was highly prevalent in the well-maintained elderly, being rarely found in GAP patients. This is evidence for regarding C. ochracea as a marker organism for periodontal health.
Considering that periodontitis is a polymicrobial infection, the screening of the microbial population, rather than the isolation of single members of the subgingival flora, should give a more comprehensive perspective in research of etiopathogenesis of the different forms of periodontitis.
The described oligonucleotide probes allow, in combination with PCR-amplification and dot-blot hybridization, a specific and sensitive detection of the respective oral species. Subsequent epidemiological studies using identical molecular genetic detection methods, as well as the investigation of complex subgingival biofilms by applying oligonucleotide probes in a fluorescence-in-situ hybridization, are in progress.