Session 5: Plaque Formation and Retention Flashcards
What is Dental Plaque Biofilm
Dental plaque is defined clinically as a structured, resilient, yellow-grayish substance that adheres tenaciously to the intraoral hard surfaces, including removable and fixed restorations
Structure of a Biofilm
- Mushroom shaped colonies, own customized living environment
- Extracellular slime layer protects the bacterial colonies from antibiotics, antimicrobials and host
response
– Fluid channels extend through the slime layer to help with movement of nutrients throughout the biofilm and rid itself from waste products
Clinical Appearance of Dental Biofilm
– Dense, non-calcified, highly organised bacterial mass. yellow to grey in colour
– Accumulates over time on teeth / hard materials in the mouth
– Collects rapidly in inaccessible areas of the mouth
– Can be seen as white to off white accumulation of variable thickness
– Without disturbance, the plaque can form up to the height of the crown
Distribution of Dental Plaque Biofilm
Adherence to Surfaces • Calculus (calcified dental plaque) • Restorations • Appliances – dentures Location of Plaque • Supragingival • Subgingival plaque
Composition of Dental Biofilm
Matrix (50-70%) + Microorganisms (30-50%)
- Proteins (from saliva)
- Carbs - Leukocytes, erythrocytes
- Cell remnants
- Food Debris – becomes incorporated in plaque
- Bacterial enzymes – collagenases, proteases
- Endotoxins – provoke inflammation and an immune response
- Lactic Acids – produced by bacteria as by-product of carbohydrates
- Mineral salts- calcium, phosphorous, magnesium, sodium and potassium
What are the 5 phases of plaque formation
- Clean surface
- Film Coating (Phase1)
- Initial reversible attachment of free swimming micro-organisms to surface (Phase2)
- Multiplication - Permanent chemical attachment, single layer, bacteria begin making slime (Phase3)
- Continued growth - Early vertical development (Phase 4)
- Multiple towers with channels between, maturing biofilm (Phase 5)
Phase 1 - Film coating
– Structureless film of salivary glycoprotein forms on surface of new cleaned tooth
– Forms within minutes of brushing and requires friction to remove it. Becomes populated within minutes of formation
– Helps heal, protect and repair enamel surface
– 2 Layers :
– Thin-difficult to remove
– Thicker and globular (easy to detach)
Phase 2 - Binding of Single Organisms
– Few hours after the formation of the pellicle, bacteria attach to the outer surface
– Bacteria can have extracellular substances and fimbriae to enable them to attach to the tooth
Phase 3 - Multiplication
– Bacteria stick to the teeth
– Bacteria produce substances that stimulate other free-floating bacteria to join the colony
Phase 4 - Continued Growth
Extracellular Slime Formation & Microcolony Formation
– Extracellular slimy layer help glue bacteria together
– Bacteria are stimulated to excrete slimy, glue-like substance. Anchors bacteria to tooth surface
– Provides protection for attached bacteria
– Bacterial population initially grows along the cervical areas then spread over and away from the tooth surface
Phase 5 - Mature Biofilm
– Biofilm formation is rapid then slows down in more mature plaque
– At 24 hours, biofilm becomes visible to the human eye
– Between 24-48 hours, the flora becomes increasingly complex with an increase in anaerobic bacteria (predominate)
– As plaque (biofilm) ages gram + organisms reduce
– Number of cocci decreases while filaments and spirochetes increase
– In deeper layers of mature plaque- dead, inactive bacteria and degraded matrix present
– After 2 weeks, no major changes to structure and composition of plaque
3 Zones of Subgingival Plaque
- Tooth Associated
- Bacteria attached to the tooth surface. From gingival margins to base of JE. Has ability to invade dentinal tubules. Inner layers = Gram+ bacteria - Tissue Associated (epithelium)
- Bacteria attached to the epithelium pocket wall. Invade the gingival connective tissue and be found on the surface of the alveolar bone - Unattached Bacteria
- Periodontal pocket contains free-floating bacteria that are not part of the biofilm.
What is Bacterial Virulence Factors?
- Mechanisms that enable biofilm bacteria to colonize, invade, and damage tissues of the periodontium
- May be structural characteristics of the individual bacterium
- May be substances produced and released by bacteria
How endotoxins and exotoxins invade and damage periodontal tissues
1) Endotoxins (Lipopolysaccharides or LPS)
–Released when the cell walls of bacteria begin to break up. This stimulates biologic activities
–Promote tissue destruction and bone resorption
–Breakdown of collagen fibers in gingival connective tissue through ulcerations of epithelial lining
2) Exotoxins
– Harmful proteins released from the bacteria that act on host cells from a distance
– Eg. Aggregatiabacter actinomycetemcomitans produces leukotoxins that destroy leukocytes in periodontal pocket or sulcus
– Bacterial enzyme production
– Enzymes are agents that are harmful or destructive to host cells by:
. Increasing permeability of epithelial lining of sulcus
. Contributing to breakdown of collagen fibers in gingival connective tissue
. Promoting apical migration of junctional epithelium along root
. Causing widening of intercellular spaces
. Diminishing ability of immunoglobins and other proteins in defending the host
Compare and contrast Material Alba, Dental plaque and Calculus
1) Material Alba
- Structure-less mixture of bacteria, food debris, dead epithelial cells, leukocytes and salivary deposits. It can be removed easily and washed away with water spray. White cheese like
accumulation
2) Dental Plaque
- Primarily composed of bacteria in a matrix of salivary glycoproteins and extracellular polysaccharides. Biofilm. Use toothbrush to remove. Clear to yellow-grayish substance
3) Calculus
- Yellow-Black hard deposit that forms via the mineralization of dental plaque. Generally covered by a layer of unmineralized dental plaque. Requires scalers to remove
