Dental Plaque Flashcards
What is the definition of dental plaque
This is a general term for the complex microbial community embedded in a matrix of salivary and bacterial origin (biofilm) and found on the tooth surface
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Bacteria gorwingin a biofilm are different to the same cells in a liquid phase/culture
What are the general properties of a biofilm
- Protection from desiccation, host defences/predators and antibiotics
- Slow growth rate
- Spatial and environmental heterogeneity - leads to metabolic interactions
- Surface associated physical characteristics
What are the micro-organisms in dental plaque more resistant to
They have a reduced sensitivity to chlorhexidine and antibiotics
What are the benefits of being an organism in a biofilm
- Enzyme complementation/sharing
- Food chains
- Co-adhesion
- Cell-cell signalling
- Gene transfer
- Environmental modifications
What are the disadvantages of being an organism in a biofilm
- Bacteriocin production
- H2O2 production
- Organic acid production/generation of inhibitory pH conditions
- Bacteriophage release
- Competition for essential nutrients
- Predation
Where can you find dental plaque around and on a tooth
Fissure plaque - in between cusps
Approximate plaque- between teeth
Gingival crevice plaque - in the crevice between the enamel and gingiva - junctional epithelium?
Denture plaque
What is the difference between plaque and calculus
Calculus is calcified plaque
What is the first step of the development dental plaque
- the acquired enamel pellicle forms almost immediately, complete 2 hours after cleaning
What is the acquired pellicle made up of
Composed of proteins, lipids and glycoproteins from bacteria, saliva and gingival crevicular fluid
What can also be found in the acquired pellicle from bacteria and what do these act as
Glycosyl transferases
Glucans, Fructans
Bacterial cell fragments
These bacteria derived components act as receptors for bacterial adhesion
What can also be found in the acquired pellicle from the host and what do these act as
Acidic, proline rich proteins - promotes adherence of bacteria
- Amylase
- Lysozymes
- Albumin
- Immunoglobins
What is the second stage of the development of the dental plaque
The pioneering species of bacteria will adhere to the acquired pellicle
How do bacteria attach to the pellicle/tooth surface
- Passive transport of bacteria to the tooth surface
- Attachment of bacteria to pellicle:
Vt = Va + Vr
Va = Van der Waals forces
Vr = electrostatic repulsion between negatively charged bacterial cell and pellicle surface
What is the name of the particles used by bacteria to attach to the tooth surface/pellicle
Adhesins
Name some receptors in the pellicle/tooth surface that bacteria adhere to
Salivary agglutinin (streptococci)
Glycoproteins (streptococci)
Glucan (Mutans streps)
Proline rich proteins (Actinomyces Naeslundii)
Name some adhesins that bacteria use to bind to the tooth surface/pellicle
Protein antigens (Streptococci)
Lipoteichoic acid (streptococci)
Glucan binding protein (mutans streps)
Fimbrae (Actinomyces Naeslundii)
What is the third stage of the development dental plaque
Pioneering species multiply and form a confluent layer
What can bacteria start to do in the third stage of the development of dental plaque
Ability to utilise salivary glycoproteins via glycosidases
Ability to cleave IgA via IgA proteases
Also able to use bacterial polysaccharides
What is co-aggregation in the third stage of development of dental plaque
Cell-Cell interactions leading to distinctly different bacterial species becoming predetermined partners in forming plaque
Give some examples of species that co-aggregate
Strep. sanguinis or S. mitis with Actinomyces spps, Corynebacterium matruchotii or propionibacterium acnes
What is co-adherence
Term sometimes used for cell-cell adhesive interaction on a surface rather than in suspension
What happens in the 4 stage of dental plaque development
Accumulated bacterial growth leads to:
- decreased oxygen tension
- Eventual growth of anaerobic bacteria
- Increased diversity
What is the 5th stage of dental plaque development
Plaque maturity
What are the main bacteria found on the in dental plaque during plaque maturity
Streptococci-15%
Actinomyces
Anaerobic rods and filaments increase
What is accumulation of bacteria on the teeth a result of
A balance between adhesion, growth of bacteria and removal of bacteria via physical forces and plaque interactions/competitions
Once the dental plaque has developed a microbial homeostasis what are the benefits to the bacteria
- Enhanced catabolism of endogenous nutrients.
- Protection from stressful environments
- Organisms within the community can persist and grow over a wider habitat range.
- Organisms can display synergy in the recycling of nutrients.
- Metabolic efficiency of the community is increased.
How can a small amount of dental plaque benefit us
Can prevent pathogenic species form entering and becoming established in the mouth
How do the bacteria in plaque exclude exogenous organisms
- Competition for adhesion receptor sites
- Comepetition for nutrients and co factors
- Production of inhibitory substances like acids and H2O2
How does the host interact with the dental plaque
Immunity from lysozymes, lactoferrin and peroxidases interact with the plaque and inhibit its growth
What does calculus consist of
Mineral deposits, protein and carbohydrates
from host and bacteria
Where is calculus usually found
Can be supra gingival esp. near salivary ducts or subgingivally in association with dental plaque
What does the porosity of calculus cause
Cause retention of bacterial antigens and may be involved with bone resorption
How common is calculus
More than 80% of adults have it and increases with age - difficult to remove
Name some Gram positive cocci found in dental plaque
Streptococcus
Staphylococcus
Abiotrphia
Peptostreptococcus
Name some Gram negative cocci found in dental plaque
Neisseria
Veillonella
Name some gram positive rods found in dental plaque
Actinomyces Eubacterium Corynebacterium Bifidobacterium Lactobacillus
Name some gram negative rods found in dental plaque
Actinobacillus Campylobacter Capnocytophaga Porphyromonas Wolinella Treponema
The stagnant sites in denture plaque build up what kind of bacteria
Streptococci and candida sp. - acidogenic
C. albicans