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Dental Plaque :

Dental Plaque Dr. Shafaq Salim


Definitions Soft 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.

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Dental plaque must be differentiated from other tooth deposits, like materia alba and calculus. Materia Alba soft accumulations of bacteria and tissue cells that lack the organized structure of dental plaque. Calculus hard deposits formed by mineralization of dental plaque and is generally covered by a layer of un- mineralised plaque.

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It can only be detected clinically after it has reached a certain thickness but small amount can be made obvious when stained with disclosing agents (disclosing tablets). In stagnation areas, the bacteria in dental plaque can form acids from sugar in the mouth over a period of time which attack tooth surface

Plaque Index:

Plaque Index Score Criteria: 0 No plaque 1 A film of plaque adhering to the free gingival margin and adjacent area of the tooth, which can not be seen with the naked eye. But only by using disclosing solution or by using probe. 2 Moderate accumulation of deposits within the gingival pocket, on the gingival margin and/ or adjacent tooth surface, which can be seen with the naked eye. 3 Abundance of soft matter within the gingival pocket and/or on the tooth and gingival margin.


Composition Bacterial 70-80% (1 mg of dental plaque is estimated to contain 250 million bacterial) All the materials among the bacteria in the plaque are referred to as INTER MICROBIAL MATRIX. The organic inter-microbial matrix includes: Polysaccharide complex produced by bacteria Glycoprotien from saliva Lipids from debris Fungi epithelial cells, leukocytes, macrophages. The inorganic inter-microbial matrix include: Calcium Phosphorous Magnesium Potassium Sodium etc

Classification :


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Plaque.. Disease it can lead to.. Marginal plaque Gingivitis Supra-gingival plaque Calculus formation & Root caries Sub -gingival plaque Soft tissue destruction & Periodontitis

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Supra-gingival plaque Sub-gingival plaque Contains 50% matrix It contains mostly gram+ve Has few motile bacterial It’s aerobic unless it’s thick It ( bacteriae ) metabolizes predominantly carbohydrates. if allowed to grow can lead to gingivitis and it influences the growth, accumulation and pathologic potential of subgingival plaque. Has little or no matrix Mostly gram- ve Motile bacterial is common Highly anaerobic area is present Predominantly metabolizes protein. associated with enlarged gingiva , calculus formation, periodontitis

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3 points to explain in this dia, Mechanism of gingivitis & periodontitis formation Growth mechanism (metabolization of protein) in sub-gingival.


Attached plaque (in relation to tooth, epithelium, connective tissues etc) Tooth associated sub-gingival plaque Grams-positive cocci , rods, filamentous bacterial, and few grams – ve . Epithelial associated sub-gingival plaque, It is loosely adherent. It is in direct contact with the gingival epithelium, extending from the gingival margin to the junctional epithelium. This dominantly contains grams – ve rods and cocci , large number of flagellated bacteria and spirochete. Unattached subgingival plaque. The unattached plaque can be seen everywhere and is associated with rapid periodontal destruction. Coronal plaque which is in contact with only the tooth surface Marginal plaque associated with the tooth surface at the gingival margin. Supra-gingival Sub-gingival

Development of plaque:

Development of plaque


SELECTED BACTERIAL SPECIES FOUND IN DENTAL PLAQUE Facultative Gram-Positive Streptococcus mutans Streptococcus sanguis Actinomyces viscosus Gram-negative Anaerobic Actinobacillus actinomycetemcomitans Capnocytophypa species Eikenella corrodens Porphyromonas gingivalis Fusobacterium nucleatum Prevotella intermedia Bacteroides forsythus Campylobacter rectus Spirochetes Treponema denticola (Other Treponema species)

Relationship of Specific Micro-organisms to Periodontal Diseases :

Relationship of Specific Micro-organisms to Periodontal Diseases Early in the 19th century, it was felt that, a specific bacterial species was responsible for the disease processes. The criteria by which a given bacterial species was associated with disease historically has been through the application of Koch's Postulates.


Robert koch criterias-late 1800

Specific Plaque Hypothesis (Loesche,1976 :

Specific Plaque Hypothesis (Loesche,1976 The Specific Plaque Hypothesis states that disease results from the action of (one or several) specific pathogenic species and is often associated with a relative increase in the numbers of these organism found in plaque.

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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.

Non-Specific Plaque Hypothesis (Loesche,1976) :

The nonspecific plaque hypothesis maintains that periodontal disease results from the “elaboration of noxious products by the entire plaque flora.” Control of periodontal disease depend on the control of amount of plaque accumulation. This concept, known as the Non-Specific Plaque Hypothesis ( Loesche , 1976), held that all bacteria were equally effective in causing disease. Non-Specific Plaque Hypothesis (Loesche,1976)

Benefits of dental plaque:

Benefits of dental plaque They play a critical role in, In mineralization of early carious lesions (white spot) It reduces the risk of infection by acting as a barrier to colonization by exogenous species termed colonization resistance . Reduction of colonization resistance can result in overgrowth of microflora , establishment of exogenous species which can lead to pathological changes.



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