Dental Plaque Formation and Microbiology

Microbiology of Periodontal Diseases

• The study focuses on the microbiology of periodontal diseases
• Learning objectives include understanding tooth deposits, bacterial complexes, bacterial interactions, and correlating treatment to microbial reasons.

Learning Objectives

• Different tooth deposits, their formation, implications on diseases
• Various bacterial complexes and families found in periodontal disease
• Bacterial interactions in various periodontal diseases
• Correlation between periodontal treatment and microbial reasons

Bacterial Timeline (Months After Birth)

• Gram-negative bacteria like Veillonella, Prevotella, and other species are prevalent at various stages, from the initial stages shortly after birth to several years later
• Gram-positive bacteria like Actinomyces, Streptococcus, and other species are also shown in the chart
• Different bacteria are present at different times after birth, exhibiting complex developmental patterns

Types of Tooth Deposits

• Dental plaque: a soft biofilm adhering to tooth surfaces, restorations
• Materia alba: soft accumulations of bacteria and cells, easily removed
• Calculus: hard deposit formed by dental plaque mineralization.

Oral Microbiota

• Composed of commensal, symbiotic, and pathogenic species
• Located in different niches such as the gums, saliva, and teeth
• Biofilms are communities of bacteria attached to surfaces

Six Major Ecosystems

• Intraoral and supragingival hard surfaces (teeth, implants)
• Subgingival regions adjacent to hard surfaces (periodontal/periimplant pockets)
• Epithelium of the buccal and palatal areas, mouth floor, tongue dorsum, tonsils
• Saliva

Dental Plaque Composition

• Microorganisms (70%): Various bacterial strains, non bacterial (e.g., yeasts, protozoa, viruses)
• Intercellular Matrix (30%): Organic materials (e.g., glycoproteins, polysaccharides (dextran), albumin, lipids ) plus inorganic materials(e.g., calcium, phosphorus, sodium, potassium, fluoride)

Plaque Formation Process

• Pellicle formation on tooth surfaces (glycoprotein pellicle from saliva, crevicular fluid, bacterial and host cells)
• Initial colonization involves gram-positive bacteria like Actinomyces and Streptococcus, attaching using adhesins to the pellicle
• Secondary colonization, with additional species attaching to existing organisms (coaggregation)
• Plaque maturity includes a transition from an early aerobic environment with gram-positive facultative species to a highly anaerobic environment.

Formation of Dental Plaque-Phases

• 1. Pellicle Formation: Initial coating on the tooth surface created by glycoproteins, bacteria, and proteins from saliva & crevicular fluid
• 2. Initial Colonization: Gram-positive, facultative bacteria (Streptococci, Actinomyces) attach to the pellicle.
• 3. Secondary Colonization: Additional bacteria (e.g., Prevotella, Porphyromonas) now attach to existing bacteria
• 4. Plaque Maturation: A transition occurs to a more anaerobic environment with higher numbers of gram-negative anaerobic bacteria.

Different Plaque Regions and Associated Diseases

• Supragingival plaque leads to calculus and caries, gingivitis
• Subgingival plaque leads to calculus, caries, and soft-tissue destruction.

Microbial Specificity of Periodontal Diseases

• Nonspecific plaque hypothesis: Plaque accumulation regardless of specific bacteria is a primary factor.
• Specific plaque hypothesis: Specific bacteria or their products are the primary factors in disease.
• Ecological plaque hypothesis: The interaction with other bacteria and the environment leads to specific diseases, and the different clusters affect the other clusters according to the periodontal state.

Microorganisms Associated with Specific Diseases

• Periodontal Health: Primarily gram-positive facultative species (including Streptococcus, Actinomyces).
• Gingivitis: Almost equal proportions of gram-positive and gram-negative species.
• Pregnancy-associated gingivitis: Prevotella intermedia use steroids as growth factors.
• Chronic Periodontitis: High percentages of anaerobic gram-negative bacteria, including Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Bacteroides forsythus.
• Localized Aggressive Periodontitis: High levels of A. actinomycetemcomitans.
• Abscesses of the Periodontium: F. nucleatum, P. intermedia, P. gingivalis, P. micros, and B. forsythus.

Controlling Dental Plaque/Biofilm

• Mechanical removal is the most effective treatment method.

Plaque Index

• Simple method for evaluating plaque on teeth using disclosing tablets. Calculation involves determining the number of sites with plaque and comparing it to the total number of sites evaluated.

Additional Considerations

• Study of biofilm emphasizes the community aspects of bacteria and their intricate interactions, rather than isolated pathogens.
• Multiple bacteria species' interdependence and influence on one another highlight the complexity within periodontitis.