Periodontal Microbiology Quiz

Microbiology of Periodontal Diseases

• The periodontal microbiota is extremely complex
• It affects the host, the oral environment, and periodontal treatment
• Profound knowledge of periodontal microbiology is necessary

Learning Objectives

• Understand different tooth deposits, their formation, and disease implications
• Recognize different bacterial complexes and families involved in periodontal disease
• Comprehend bacterial interactions during various periodontal diseases
• Correlate periodontal treatments to the microbial reasons

Bacterial Types

• Gram-negative bacteria

  • Veillonella spp.
  • Prevotella spp.
  • Haemophilus spp.
  • Neisseria spp.
  • Fusobacterium
  • Porphyromonas gingivalis
  • Capnocytophaga spp.

• Gram-positive bacteria

  • Actinomyces spp.
  • Actinomyces odontolyticus
  • Streptococcus mitis
  • Streptococcus sanguinis
  • Streptococcus oralis
  • Streptococcus salavanus
  • Staphylococcus
  • Streptococcus
  • Clostratium spp

• Other Bacteria

  • Corroding rods
  • Other Fusobacteria
  • Aggregatibacter actinomycetemcomitans
  • Porphyromonas gingivalis

Different Deposits on Teeth

• Dental plaque: A soft biofilm that adheres to tooth surfaces, including restorations
• Materia alba: Soft accumulations of bacteria and tissue cells; easily displaced
• Calculus: A hard deposit formed by mineralization of dental plaque
  • Generally covered by a layer of unmineralized plaque

Dental Plaque = Biofilm

• Dental plaque is the primary etiologic factor for gingivitis and periodontitis
• It is a microbial community with a complex structure
• It increases resistance to antimicrobial agents due to limited diffusion of substances

Composition of Dental Plaque

• Microorganisms (70%)
  • More than 500 bacterial strains; non-bacteria (e.g., yeasts, protozoa, viruses)
• Intercellular Matrix (30%) - Organic materials (e.g., glycoproteins, polysaccharides, albumin, lipids) - Inorganic materials (e.g., calcium, phosphorus, sodium, potassium, fluoride)

Organic Materials in Plaque

• Glycoproteins, derived from saliva and important for pellicle formation
• Polysaccharides, produced by bacteria (e.g., dextran)
• Albumin, derived from crevicular fluid
• Lipids, debris from disrupted cells and food

Inorganic Materials in Plaque

• Calcium and phosphorus
• Sodium, potassium, and fluoride

Bacterial Lifestyles

• Free-floating (planktonic)
• Attached to a surface forming a biofilm community

Biofilm Communities

• A biofilm is a well-organized community of bacteria adhering to surfaces
  • Embedded in an extracellular slime layer
• More than 99% of bacteria on Earth are attached bacteria in biofilms
• Found on many medical and dental devices

Formation of Dental Plaque

• Different factors influence the location and rate of plaque formation (oral hygiene, diet, salivary composition, saliva flow rate)
• In the absence of oral hygiene, plaque accumulates until a balance between removal and formation is reached
• Plaque formation happens in 3 phases
  • Formation of the pellicle on the tooth surface
  • Initial colonization by bacteria
  • Secondary colonization
  • Plaque maturation

Initial Colonization of Plaque

• Bacteria are found within a few hours on the dental pellicle
• Predominantly gram-positive facultative microorganisms (e.g., Actinomyces viscosus, Streptococcus sanguis)
• Adherence to pellicle via specific molecules called adhesins on the bacterial surface

Secondary Colonization & Plaque Maturation

• Secondary colonizers are microorganisms that do not initially colonize clean surfaces
  • e.g., Prevotella intermedia, Prevotella loescheii, Capnocytophaga spp., Fusobacterium nucleatum, Porphyromonas gingivalis
• They often adhere to pre-existing cells in the plaque

Coaggregation

• Interactions among different gram-positive bacteria
• Then between gram-positive and gram-negative species
• Between different gram-negative species in later stages

Microbial Ecology and Interactions

• Bacteria are classified into 5 clusters based on nutritional and atmospheric similarities/differences
• Interactions between clusters influence each other, related to specific periodontal states
• Species from certain clusters are found interacting with others, mainly well; certain clusters rarely observed without another cluster

Microorganisms Associated with Periodontal Diseases

• Periodontal health—Gram-positive, facultative species from genera Streptococcus and Actinomyces
• Gingivitis—equal proportions of gram-positive and gram-negative cocci, rods, and filaments
• Pregnancy-associated gingivitis—P. intermedia
• Chronic periodontitis—high percentages of aerobic bacterial species and P. gingivalis, P. intermedia, F. nucleatum, B. forsythus
• Localized aggressive periodontitis—A. actinomycetemcomitans is prominent with Herpesviruses (EBV-1 and HCMV) as potential factors
• Abscesses—F. nucleatum, P. intermedia, P. gingivalis, P. micros, and B. forsythus

Plaque Index

• A method for measuring plaque levels
• Plaque stained by tablets
• Calculation: (Number of sites with plaque / Number of sites evaluated) x 100

Controlling Dental Plaque Biofilm

• Mechanical removal is the most effective treatment

Plaque Hypothesis

• Nonspecific plaque hypothesis
• Specific plaque hypothesis
• Ecological plaque hypothesis