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INTERDISCIPLINARY
periodontal disease also appeared to change little
in the face of significant dietary changes and the advent
of antibiotics. From early humans to modern times,
subtle trends include a decrease in non-pathogenic
clostridia taxa and members of the Ruminociccaceae
family, and an increased frequency of caries-associated
Veillonellaceae, Lachnospiraceae, and Actinomycetales.
Notably, the frequency of S. mutans is significantly
higher in modern samples than in preindustrial
agricultural samples . It is reasonable to point out,
however, that DNA sequences buried in ancient
calculus sampled to compare to modern viable
microbiomes may not be representative of the loose
plaque biofilm directly facing the epithelium of the
periodontal pocket or sites on the tooth surface that
are susceptible to caries.
genetic diversity is associated with greater ecosystem
resilience the decreased diversity of the modern oral
environment may be associated with less resistance
to perturbations and greater susceptibility to insertion
of pathobionts or even true pathogens in the
microbial community Whereas this hypothesis has yet
to be tested, the microbiota of different ecological
niches within the oral cavity may reflect greater or
less stability over time.
SALIVA AND SALIVARY CONSTITUENTS
The tissues and surface biofilms of the oral cavity are
constantly immersed in saliva. The myriad proteins
and glycoproteins in saliva provide lubrication for
mastication and gustatory sensation, and both
support and antagonize biofilm formation In
conditions of nutrient deprivation, bacteria in the oral
milieu show consortial behavior to facilitate metabolism
of specific salivary glycoproteins as a nutrient source
A salivary film conditions the enamel of the tooth
crown. In the salivary film, salivary proteins (glycoproteins) are available to interact with microbial adhesins
of pioneer colonizers as modeled in vitro, facilitating
the initiation of biofilm formation on the tooth surface
Expression of adhesins is dynamic and responsive to
the adhesion status of the pioneer colonizer As the
July-August-September 2019
salivary film transitions from the crown into the gingival
sulcus, the composition changes and the proportion
of serum proteins increases due to the proximity with
the gingival crevicular fluid (GCF) With the adsorption
of serum proteins, the composition of the dental
biofilm also changes from predominantly pioneer
Streptococci and Actinomyces species.
MICROBIOTA ON TEETH
Unlike the shedding surfaces of the oral epithelia, the
tooth surfaces are the only “non-shedding” surfaces
in the oral cavity. The non-shedding surfaces facilitate
a stable anchoring location for long-term biofilm
development. As a substrate for biofilm formation, the
surfaces of the teeth are more complex than the
hydroxyapatite mineral of the enamel forming the
crowns and the cementum, which coats the roots.
The tooth enamel in the mouth is coated with a
salivary film, whereas the roots can be coated with an
admix of salivary and serum proteins. The protein-rich
films are the actual sites of initial adhesion of the
pioneer microbial colonizers reviewed in Pioneer
streptococcal adhesins initially bind the salivary film
of the enamel via “catch-bond” or shear-enhancement
interactions, requiring sheer-induced conformational
changes in the adhesins .As the biofilm matures, the
community becomes more complex. During maturation,
the changing architecture of the dental plaque
biofilm reflects the forces of interspecies coaggregation
more than new interactions between early tooth
colonizers with the salivary film.
MICROBIOTA OF PERIODONTAL DISEASE
Since the 1950s, the microbiota of the periodontal
pocket has been studied with culture methods.
Investigators sought to define the microbial species
critical for the initiation and progression of the
disease. Defined historically as microorganisms of the
“red complex” by Sigmund Socransky, P. gingivalis,
Tannerella forsythia and Treponema denticola were
considered the cultivable microorganisms most
associated with disease as defined by deep
periodontal pockets .
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