Plaque formation and retention Flashcards
Describe the composition of dental plaque biofilm
50%-70% MATRIX, and 30%-50% microorganisms
The matrix consists of:
• Proteins- derived from saliva
• Dietary carbohydrates (small amounts)
• 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
Describe the structure of dental plaque biofilm
• Mushroom shaped colonies
• Each community has its own customized living environment
• Extracellular slime layer: protects the bacteria 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
Describe the clinical appearance and distribution of dental plaque biofilm
• Dense, non-calcified, highly organised bacterial mass
• It accumulates over time on teeth / hard materials in the mouth, especially in inaccessible areas of the mouth – cervical region, pits and fissures and interproximal surfaces
• Can be seen as white to off white accumulation of variable thickness. Mature plaque is yellow to grey in colour
* It can be located sub-gingivally or supra-gingivally
Recall the physiological properties of dental plaque and calculus
• Dental plaque and calculus adheres to teeth and other solid objects within the oral cavity
• The first bacteria to colonize the tooth surface are nonpathogenic
• Periodontal pathogens are UNABLE to colonize the biofilm until the nonpathogenic species are attached
• Calculus is just mineralised dental plaque
* Not common on primary dentition – increasingly common from teen years into adulthood
Describe the 5 phases of plaque formation
- Film Coating (Phase1)
• Structure less film of salivary glycoprotein that forms on the surface of a newly cleaned tooth. It forms within minutes of brushing and requires friction to remove it
• Helps heal, protect and repair enamel surface
• Becomes populated with bacteria within minutes of formation - Initial reversible attachment of free swimming micro-organisms to surface:
• Within a 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 - Permanent chemical attachment, single layer, bacteria begin making slime:
• Bacteria stick to the teeth
• Bacteria produce substances that stimulate other free-floating bacteria to join the colony
• Extracellular slimy layer is formed to help glue the bacteria together - Early vertical development:
• Bacteria are stimulated to excrete slimy, gluelike substance. It helps anchor bacteria to tooth surface and provides protection for attached bacteria
• Bacterial population initially grows along the cervical areas of the teeth then spread out over and away from the tooth surface - Multiple towers with channels between, maturing biofilm:
• Biofilm formation is rapid then slows down in more mature plaque
• The microflora becomes increasingly complex;- Increase in anaerobic bacteria
- Gram + organisms reduces
• Number of cocci decreases and spirochetes increass
• In deeper layers of mature plaque- dead, inactive bacteria and degraded matrix present
Recall and explain the differences amongst the 3 zones of subgingival plaque
- Tooth associated
• Plaque attaches and extends from the gingival margins to the base of the junctional epithelium
• Appears to have the ability to invade the dentinal tubules of the cementum
• Inner layers are dominated by gram positive bacteria
* Gram negative bacteria are also present - Tissue associated (epithelium)
• Adhere to the epithelium of the pocket wall
• Are distinctly different from the tooth-associated bacteria
• Can invade the gingival connective tissue and be found on the surface of the alveolar bone
* Research suggests that tissue-associated plaque is the most detrimental to the periodontal tissues - Unattached bacteria
* In addition to the attached bacteria, the periodontal pocket contains free-floating bacteria that are not part of the biofilm.
Define bacterial virulence factors
Virulence factorsare molecules that add to their effectiveness and enable them to achieve the following:
• Colonization of a niche in the host (this includes attachment to cells)
• Immunoevasion, evasion of the host’s immune response
• Immunosuppression, inhibition of the host’s immune response
• Entry into and exit out of cells (if the pathogen is an intracellular one)
• Obtain nutrition from the host
Describe how endotoxins and exotoxins invade and damage periodontal tissues
Endotoxins
• Lipopolysaccharides(LPS), also known as lipoglycans andendotoxins, are largemoleculesconsisting of alipidand apolysaccharide. They are found in theouter membraneofGram-negative bacteria
• It is released when the bacterium ruptures or disintegrates
• When released, it promotes;
* tissue destruction
* bone resorption
* breakdown of collagen fibers
Exotoxins:
• Harmful proteins and enzymea released from the bacteria that act on host cells from a distance
* 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
○ Immunosupression and immunoevasion
Describe materia alba
- White cheese like accumulation
- Soft accumulation of salivary proteins, some bacteria, many desquamated epithelial cells, and occasional disintegrating food debris
- Lacks an organized structure and is therefore not as complex as dental plaque
- Easily displaced with a water spray
Describe dental plaque
- Resilient clear to yellow-grayish substance
- Primarily composed of bacteria in a matrix of salivary glycoproteins and extracellular polysaccharides
- Considered to be a biofilm
- Impossible to remove by rinsing or with the use of sprays (toothbrush can remove)
Describe 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
Discuss the control of biofilm
- Current research shows that the body’s immune response to the plaque biofilm is the primary cause of the destruction seen in periodontitis
- Biofilm bacteria are EXTREMELY resistant to antibiotics, antimicrobial agents, and the body’s immune system.
- The extracellular slime layer protects from drugs and the body’s leukocytes.
- Some bacteria produce enzymes that degrade antibiotics faster than the drug can penetrate into the biofilm.
- Bacteria in the deepest layers of the biofilm become dormant. Antibiotics only work on bacteria that are active and reproducing
- When a course of antibiotics is finished, the dormant bacteria within the biofilm reactivate
- Control of bacteria in dental plaque biofilms is best achieved by the physical disruption of the plaque biofilm (such as brushing, flossing, and periodontal instrumentation).
Compare and contrast characteristics of supra- and sub-gingival calculus
Supra gingival • Hard, brittle material that is relatively easy to detach for the tooth surface with a suitable instrument • Light yellow in colour • Occasionally stained • Minerals are derived from saliva • Could be deposited anywhere on teeth
Sub gingival
• Yellow, dark green, brown or black in colour
• Minerals are derived from the gingival crevicular fluid
• Detection during clinical examination and radiographs
• Often generalised
• Location is related to the presence of gingival inflammation and pocketing
* Harder than supragingival calculus and more firmly adherent to the tooth surface
