23-08-2013, 04:48 PM
Dental Plaque
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Definitions
According to Bowden, Dental plaque can be defined as the soft tissue deposits that form the biofilm adhering to the tooth surface or on the other hard surfaces in the oral cavity, including removable and fixed restorations.
According to Marsh, Dental plaque can be defined as the diverse community of microorganisms found on the tooth surface as a biofilm, embedded in an extracellular matrix of polymers of host and microbial origin.
Plaque
Plaque can be defined as a complex microbial community, with greater than 1010 bacteria per milligram. It has been estimated that as many as 400 distinct bacterial species may be found in plaque.
In addition to the bacterial cells, plaque contains a small number of epithelial cells, leukocytes, and macrophages. The cells are contained within an extracellular matrix, which is formed from bacterial products and saliva.
The extracellular matrix contains protein, polysaccharide, lipids and glycoproteins
Dental plaque can be classified in several different ways.
Plaque is classified as supragingival or subgingival based on its relationship to the gingival margin. Supragingival plaque is evident on the tooth above the gingival margin
Plaque can also be classified by its relationship to the tooth surface, as either attached or unattached plaque.
The unattached subgingival plaque is more closely associated with the wall of the subgingival tissues than is the attached plaque.
Lastly, plaque has been classified by association with disease state as "health-associated" or "disease-associated".
The latter classification is related to differences in the microbial composition of dental plaque in health versus disease.
Development of dental plaque
The development of dental plaque has been studied in humans as well as non-human animal model systems.
One of the most commonly used models of plaque development is referred to as the "experimental gingivitis" model (Loe, et al., 1965).
This protocol involves the examination of subjects (usually dental students!) who abstain from any oral hygiene measures for a period of three weeks.
These studies have provided much information on the structural and microbiological characteristics of dental plaque.
Non-Specific Plaque Hypothesis (Loesche,1976)
However, the concept that a specific bacterial species was responsible for periodontal diseases fell out of favor for several reasons. First, despite numerous attempts, a specific bacterial agent was not isolated from diseased individuals. Rather, the organisms found associated with disease were also found associated with health.
Good experimental animal model systems of periodontal disease were not available to test the pathogenicity of specific microorganisms (this, in fact, remains problematic today).