Structural organization and composition
In modern microbiology, dental plaque is considered not merely as an accumulation of bacteria, but as a full-fledged biofilm. This is a symbiotic community that successfully functions under conditions of constant exposure to saliva (fluid flows).
The basis of the biofilm is the matrix, a robust organic substance. It is composed of:
- Clusters of various microorganisms;
- Polysaccharides;
- Specific proteins.
Practically all representatives of the normal oral flora can be found within this biotope. However, the specific microbial landscape and the number of microorganisms are not constant: they vary not only among different individuals, but also within the same person throughout their life.
The formation of this complex community is decisively influenced by the macroorganism itself, as well as a number of environmental factors. These include dietary habits, general lifestyle, and occupational hazards.
Mechanism of formation and microbial succession
The process of dental plaque formation occurs in stages and is characterized by a strict sequence of microbial community shifts.
- Initial stage. It all begins with the formation of the pellicle, a soft acellular dental deposit that covers the tooth surface and serves as a basis for the subsequent attachment of microbes.
- Adhesion and colonization. This stage takes only a few hours. There is a rapid increase in microbial biomass. During this period, unique microscopic structures known as "corn cobs" are formed. These are the result of coaggregation: numerous microorganisms of completely different species tightly adhere to a single long filamentous bacterium.
- Microbial succession (species shift). Biofilm colonization proceeds strictly according to the rules of ecological succession:
- Primary colonizers: These are aerobes and facultative anaerobes (e.g., streptococci, corynebacteria, and actinomycetes). Their main task is to consume oxygen and create oxygen-free conditions within the developing plaque.
- Secondary colonizers: As soon as the primary flora has prepared the environment, obligate anaerobes invade the plaque, for whom the absence of oxygen is critical for survival.
Clinical significance and laboratory diagnostics
Normally, the microorganisms of the biofilm are in equilibrium. However, a disruption of the quantitative and qualitative balance of symbionts, as well as an alteration in their interaction with the macroorganism, triggers the pathogenesis of major dental diseases—caries and periodontitis.
To accurately identify pathogens and assess the state of the biotope, microbiological examination is used. It consists of several strict stages:
- Sample collection: Performed extremely carefully using a dental probe or a metal spatula.
- Preparation: The collected mass must be weighed on analytical balances to precisely determine the biomass volume.
- Homogenization: To destroy the robust matrix and separate bacteria for culturing, the material is subjected to mechanical grinding or ultrasonic disintegration.
- Culturing: A quantitative method is used. Given the predominance of obligate anaerobes in the late stages of plaque formation, cultivation must be performed using anaerobic technique.
Briefly: answers to topical questions
Which specific bacterial species act as secondary colonizers of dental plaque?
Sources classify obligate anaerobes as secondary colonizers of dental plaque; they colonize the plaque after appropriate oxygen-free conditions have been established.
The indicated representatives of late dental plaque colonization include:
- Porphyromonas (Porphyromonas gingivalis)
- Prevotella (Prevotella denticola)
- Tannerella (Tannerella forsythia)
- Treponema (Treponema denticola)
- Capnocytophaga (Capnocytophaga spp.)
- Actinomyces (Actinomyces spp.)
- Aggregatibacter (Aggregatibacter actinomycetemcomitans)
Which streptococcal species play the main role in initiating dental plaque formation?
The following streptococcal species participate in the initiation of dental plaque formation during the early colonization stage:
- Streptococcus gordonii (S. gordonii)
- Streptococcus mitis (S. mitis)
- Streptococcus oralis (S. oralis)
- Streptococcus sanguinis (S. sanguinis)
These microorganisms bind to salivary receptors on the tooth pellicle: mucin, proline-rich protein, α-amylase, and salivary agglutinin.
What acids are produced by cariogenic dental plaque bacteria during carbohydrate fermentation?
During carbohydrate fermentation, cariogenic dental plaque bacteria produce organic acids.
Sources mention a specific type:
- Lactic acid is actively produced by lactobacilli during carbohydrate fermentation and dissolves the inorganic components of the tooth.
Other types of acids are not detailed, but it is noted that obligate anaerobes are capable of producing a mixture of acids upon glucose breakdown, lowering the local pH to critical values.
To remember succession: Aerobes arrive first (to consume oxygen), while Anaerobes arrive second (moving into a ready-made oxygen-free environment).
Class and exam questions
What are "corn cobs" in dental plaque formation?
These are microscopic structures arising during coaggregation, when many microorganisms of other species tightly adhere to a single filamentous base bacterium.
Which bacteria are primary colonizers?
Primary colonizers are aerobes and facultative anaerobes, primarily streptococci, corynebacteria, and actinomycetes.
What is the pathogenic role of dental plaque?
The development of caries and periodontitis is caused by a disruption of the balance (both quantitative and qualitative) between symbionts within the biofilm and the macroorganism.
What else to study on this topic
- Characteristics of the dental pellicle as a basis for bacterial adhesion
- Properties of the organic matrix: the role of bacterial polysaccharides
- Mechanisms of coaggregation and interspecies microbial interaction
- The influence of specific dietary factors on the composition of the microbial community
- Ultrasonic disintegration in microbiological practice
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