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The Oral Microbiome: A New View of Plaque Biofilm

Course Number: 676

The Sequential Theory of Colonization

It has been well established that prior to formation of the plaque biofilm, the enamel surfaces first become coated with a sticky film comprised of proteins, lipids, glycoproteins and glycolipids enabling the adherence of the primary microbial colonizers. This sticky coating is referred to as the acquired pellicle.14 Interestingly, findings from the human microbiome project revealed that most, although not all oral microbes demonstrate site specificity.14,24 An example of this site specificity is from the Streptococcus species, where S. salivarius and S. parasanguinis colonize on the dorsum of the tongue while S. sanguis and S. gordonii reside in dental plaque.24 As illustrated in the following video, primary colonizers are gram-positive rods and cocci followed by Actinomyces, Gemella, Veillonella, Rothia and Neisseria species that help facilitate attachment of F. nucleatum that is thought to play a bridging role between early and late colonizers.14

Between 18 hours to 4 days, primary colonizers predominate, however there is a slow increase in anaerobic species such as Porphyromonas, Fusobacterium, Prevotella and Capnocytophaga. These microbes situated at the dentogingival border stimulate the host immune response and both inflammation and further dysbiosis ensues with the introduction of keystone pathogens such as P. gingivalis and Filifactor alosis. It has been difficult to determine which comes first, the dysbiosis or the inflammation. There is now some speculation that this initial inflammation may be the driver of the dysbiosis.4

Figure 9. Sequential Colonization of Plaque

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