Dental Plaque as a Bioflim


Plaque as A biofilm (TU)

The term biofilm described the relatively indefinable microbial community associated with a tooth surface or any other hard, non-shedding materials. (Wildere and Charaklis 1989)

Biofilm consist of one or more communities of microorganisms embedded in glycocalyx that are attached to solid surfaces. (Costerton et al 1994)

Bacteria in the center of a microcolony may live in a strict anaerobic environment, while other bacteria at the edges of the fluid channels may live in an aerobic environment. Thus, the biofilm structure provides a range of customized living environments (with differing pHs, nutrient availability, and oxygen concentrations) within which bacteria with different physiological needs can survive.

The extracellular slime layer is a protective barrier that surrounds the mushroom shaped bacterial colonies. The slime layer protects the bacterial microcolonies from antibiotics, antimicrobials, and host defense mechanisms.

A series of fluid channels penetrates the extracellular slime layer. These fluid channels provide nutrients and oxygen for the bacterial microcolonies and facilitates movement of bacterial metabolities, waste products, and enzymes within the biofilm structure.


Characterstics of Bioflim
1. Physiological Heterogenicity within the plaque

 Cells of same microbial species can exhibit extremely different physiological states in a biofilm though separated by little distance of 10 micrometer. Also, pH can vary quite remarkably over short distances within a biofilm . Bacteria in biofilm produce several enzymes Beta- lactamase,
Superoxide dismutase, Elastases, Cellulases.

2. Quorun Sensing

Each bacterial microcolony uses chemical signals to create a primitive communication system used to communicate with other bacterial micrococlonies called as, Quorum sensing- Involves  regulation of expression of specific genes through accumulation of signaling compounds that mediate inter cellular communication.- (Prosser 1999) When these signaling compounds reach threshold level (quorum cell density), gene expression can be activated.

3. Antibiotic Resistance

 Expression of genes for antibiotic resistance and production of certain enzymes by some species in the bioflim which inactivates antibiotics or prevent their activation, at high cell densities may provide protection.

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