Ecological Succession of Biofilm in Dental Plaque

Overview of Biofilm Formation

Biofilm formation on tooth surfaces is a dynamic process characterized by ecological succession, where microbial communities evolve over time. This process transitions from an early aerobic environment dominated by gram-positive facultative species to a later stage characterized by a highly oxygen-deprived environment where gram-negative anaerobic microorganisms predominate.

Stages of Biofilm Development

1. Initial Colonization:

   • Environment: The initial phase occurs in an aerobic environment.
   • Primary Colonizers:
     • The first bacteria to colonize the pellicle-coated tooth surface are predominantly gram-positive facultative microorganisms.
     • Key Species:
       • Actinomyces viscosus
       • Streptococcus sanguis
   • Characteristics:
     • These bacteria can thrive in the presence of oxygen and play a crucial role in the establishment of the biofilm.

2. Secondary Colonization:

   • Environment: As the biofilm matures, the environment becomes increasingly anaerobic due to the metabolic activities of the initial colonizers.
   • Secondary Colonizers:
     • These microorganisms do not initially colonize clean tooth surfaces but adhere to the existing bacterial cells in the plaque mass.
     • Key Species:
       • Prevotella intermedia
       • Prevotella loescheii
       • Capnocytophaga spp.
       • Fusobacterium nucleatum
       • Porphyromonas gingivalis
   • Coaggregation:
     • Secondary colonizers adhere to primary colonizers through a process known as coaggregation, which involves specific interactions between bacterial cells.

3. Coaggregation Examples:

   • Coaggregation is a critical mechanism that facilitates the establishment of complex microbial communities within the biofilm.
   • Well-Known Examples:
     • Fusobacterium nucleatum with Streptococcus sanguis
     • Prevotella loescheii with Actinomyces viscosus
     • Capnocytophaga ochracea with Actinomyces viscosus

Implications of Ecological Succession

• Microbial Diversity: The transition from gram-positive to gram-negative organisms reflects an increase in microbial diversity and complexity within the biofilm.
• Pathogenic Potential: The accumulation of anaerobic gram-negative bacteria is associated with the development of periodontal diseases, as these organisms can produce virulence factors that contribute to tissue destruction and inflammation.
• Biofilm Stability: The interactions between different bacterial species through coaggregation enhance the stability and resilience of the biofilm, making it more challenging to remove through mechanical cleaning.

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Subgingival and Supragingival Calculus

Overview of Calculus Formation

Calculus, or tartar, is a hardened form of dental plaque that can form on both supragingival (above the gum line) and subgingival (below the gum line) surfaces. Understanding the differences between these two types of calculus is essential for effective periodontal disease management.

Subgingival Calculus

1. Color and Composition:

   • Appearance: Subgingival calculus is typically dark green or dark brown in color.
   • Causes of Color:
     • The dark color is likely due to the presence of matrix components that differ from those found in supragingival calculus.
     • It is influenced by iron heme pigments that are associated with the bleeding of inflamed gingiva, reflecting the inflammatory state of the periodontal tissues.

2. Formation Factors:

   • Matrix Components: The subgingival calculus matrix contains blood products, which contribute to its darker coloration.
   • Bacterial Environment: The subgingival environment is typically more anaerobic and harbors different bacterial species compared to supragingival calculus.

Supragingival Calculus

1. Formation Factors:

   • Dependence on Plaque and Saliva:
     • The degree of supragingival calculus formation is primarily influenced by the amount of bacterial plaque present and the secretion of salivary glands.
     • Increased plaque accumulation leads to greater calculus formation.

2. Inorganic Components:

   • Source: The inorganic components of supragingival calculus are mainly derived from saliva.
   • Composition: These components include minerals such as calcium and phosphate, which contribute to the calcification process of plaque.

Comparison of Inorganic Components

• Supragingival Calculus:

  • Inorganic components are primarily sourced from saliva, which contains minerals that facilitate the formation of calculus on the tooth surface.

• Subgingival Calculus:

  • In contrast, the inorganic components of subgingival calculus are derived mainly from crevicular fluid (serum transudate), which seeps into the gingival sulcus and contains various proteins and minerals from the bloodstream.

Plaque Formation

• Initial colonizers: Gram – positive bacteria
• Mature plaque: Shift to obligate anaerobes, proteolytic, rods, motile
• Plaque weight: 2×10¹¹ bacteria per gram

Bacterial Complexes

• Red Complex (Most pathogenic): P. gingivalis, T. denticola, B. forsythia
• Green Complex: A. actinomycetemcomitans, E. corrodens, Capnocytophaga
• BANA Test: Detects trypsin – like enzyme in T. denticola, P. gingivalis, B. forsythia

Specific Bacteria

• A. actinomycetemcomitans: Invades host cells, secretes leukotoxin (116 – kDa protein)
• P. intermedia: Increases with steroid hormones (pregnancy/puberty)
• S. oralis: Found in treated gingival sulcus
• S. sanguis: First organism on oral mucosa

⚙️ Renal Disorders

• Acute Kidney Injury:
  • Pre-renal causes: Dehydration, blood loss
  • Post-renal: Obstruction (e.g., stones, tumors)
• Nephrotic Syndrome:
  • ↑ susceptibility to CAD
  • Hallmarks: Proteinuria, hypoalbuminemia, edema, hyperlipidemia

🧪 Electrolytes & Acid-Base

• Hyperkalemia:
  • Side effect of: ACE inhibitors
  • ECG: Tall T waves, widened QRS
• Hyponatremia:
  • Watch for CNS symptoms
  • SIADH common cause in small cell lung CA

💉 Drugs & Renal Impact

• Least risk site: Atrial septal defect
• IV drug user: Tricuspid valve affected
• Common organism: Staph aureus
• Late prosthetic valve endocarditis: CoNS
• Signs:
  • Osler’s nodes – Palms & soles
  • Roth spots – Retinal hemorrhage
• Best test: Echocardiography
• Criteria: Duke’s
• Dental prophylaxis: Amoxicillin

🔻 Anemia Types

🔸 Microcytic

🔸 Macrocytic

• Pernicious anemia: ↓ intrinsic factor
• MCH ↑, MCHC normal
• Hypokalemia during treatment
• Causes: Dietary folate deficiency, celiac disease
• Thiamine deficiency → Lactic acidosis

🔸 Sideroblastic

• Causes: Hypothyroidism, INH therapy
• Treatment: Pyridoxine
• Genetic variant: Pearson syndrome

• MAP formula: Diastolic + 1/3 Pulse Pressure
• Pulse Pressure: Systolic – Diastolic
• Sphygmomanometer readings: Slightly higher than intra-arterial
• J Curve Phenomenon: Excessive BP lowering → adverse cardiac events
• Best drug for angina with HTN: Metoprolol
• Contraindicated in diabetic HTN: Thiazides
• ACEI side effect: Hyperkalemia
• Aliskiren: Direct renin antagonist