Dental Bio-Film: A Host-Specific Plaque

The significance of biofilm has been increasingly recognized in recent years because each persons’ unique biochemical environment alters the properties of the microorganisms amplifying their pathogenic potential. The biofilm community is formed through unorganized bacterial adhesion to the tooth and root surface and then through physical and physiologic interactions among different bacterial species within the microbial mass. In other words, bacteria learn to communicate, mutate and evolve through their interaction with each other and the environment to become more destructive and insulate themselves from destruction by immune and physical agents. Organized biofilms are resistant to antibiotics.

Structure and Composition of Bio-Film

Dental plaque can be defined as the sticky soft deposits that make up the biofilm adhering to the tooth or other hard surfaces in the oral cavity. Calculus is a hard deposit that forms by mineralization of dental plaque and is generally covered by a layer of unmineralized plaque. Dental plaque is a complex heterogenous community of pathogens that evolves over time.

The inter-cellular plaque matrix that holds the pathogens together, estimated to account for 20% to 30% of the plaque mass, consists of organic and inorganic materials derived from saliva, gingival fluid, and bacterial by products.

Plaque is heterogeneous in structure, with clear evidence of open fluid-filled channels running through the plaque mass. These channels seem to provide for circulation within plaque to facilitate movement of soluble molecules such as nutrients or waste products.The bacteria thrive and proliferate within the protective inter-cellular matrix through which the channels course.

Formation of Plaque

Dental plaque can be observed after 1 to 2 days of ineffective oral hygiene measures. Plaque may be white, grayish, or yellowish in appearance. Movement of the tongue, lips and cheeks and food materials over the surface of teeth results in mechanical removal of plaque on the upper two thirds of the tooth surface. Therefor plaque is typically observed at the gum line.

The process of plaque formation can be divided into three phases:

Phase 1:

Formation of an initial sticky coating called pellicle on the tooth surface.

Phase 2:

Early colonization by unorganized bacteria. Initial bacteria are predominantly gram- positive microorganisms which are more associated with dental decay. With gram-positive bacteria think not as harmful to gum health and easier to destroy.

Phase 3:

Secondary colonization of pathogens as plaque matures. There is a transition to a highly
oxygen-deprived environment in which gram-negative anaerobic microorganisms
predominate. These bacteria piggy back themselves on the bacteria already
present a process called coaggregation. Mature plaque contains predominately gram-
negative rods and cocci as well as large numbers of filaments, flagellated rods, and
spirochetes that migrate below the gum line potentially destroying the attachment and bone
around the roots of the teeth. When it comes to gram negative bacteria think the real bad
guys. Bleeding when flossing is a sign of organized destructive biofilm.

for a more detailed description see:  Dental-Plaque.pdf

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