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Questions and Answers
What characterizes secondary colonizers in dental plaque formation?
What characterizes secondary colonizers in dental plaque formation?
- They adhere to established plaque bacteria. (correct)
- They are the first bacteria to appear in the plaque.
- They initially colonize clean tooth surfaces.
- They are solely gram-positive organisms.
Which of the following shifts occurs during the transition from early supragingival dental plaque to mature plaque?
Which of the following shifts occurs during the transition from early supragingival dental plaque to mature plaque?
- An increase in gram-positive bacteria.
- A decrease in microbial population.
- A formation of singular species dominance.
- A transition to higher numbers of gram-negative bacteria. (correct)
What is the primary advantage of biofilm bacteria compared to their planktonic counterparts?
What is the primary advantage of biofilm bacteria compared to their planktonic counterparts?
- They grow more rapidly in isolation.
- They are significantly more resistant to antimicrobial agents. (correct)
- They are more virulent and pathogenic.
- They are easier to kill with antimicrobial agents.
What is the primary difference between planktonic bacteria and biofilm bacteria?
What is the primary difference between planktonic bacteria and biofilm bacteria?
How do bacteria in biofilms benefit from their interactions with neighboring cells?
How do bacteria in biofilms benefit from their interactions with neighboring cells?
Which studies identified color-coded complexes of periodontal microorganisms?
Which studies identified color-coded complexes of periodontal microorganisms?
What type of interactions are likely to predominate among different gram-negative species during the later stages of plaque formation?
What type of interactions are likely to predominate among different gram-negative species during the later stages of plaque formation?
What role do water channels serve in biofilms?
What role do water channels serve in biofilms?
What is quorum sensing in the context of bacterial biofilms?
What is quorum sensing in the context of bacterial biofilms?
What feature contributes to the heterogeneous nature of biofilms?
What feature contributes to the heterogeneous nature of biofilms?
What process enables the exchange of DNA among bacteria in a biofilm?
What process enables the exchange of DNA among bacteria in a biofilm?
What kind of gradients are typically present in biofilms that create distinct microenvironments?
What kind of gradients are typically present in biofilms that create distinct microenvironments?
What type of molecules do bacteria use in the quorum sensing process?
What type of molecules do bacteria use in the quorum sensing process?
What compound is produced by S.mutans that has broad antimicrobial activity?
What compound is produced by S.mutans that has broad antimicrobial activity?
Which mechanism allows oral streptococci to compete with S.mutans?
Which mechanism allows oral streptococci to compete with S.mutans?
How much more resistant are organisms in a biofilm compared to their planktonic state?
How much more resistant are organisms in a biofilm compared to their planktonic state?
What is a major reason for antibiotic resistance in bacteria within biofilms?
What is a major reason for antibiotic resistance in bacteria within biofilms?
What role do multidrug resistance pumps play in biofilm bacteria?
What role do multidrug resistance pumps play in biofilm bacteria?
What effect does the extracellular matrix have on antibiotics within biofilms?
What effect does the extracellular matrix have on antibiotics within biofilms?
Which oral bacteria have been shown to modulate bacteria-host interactions?
Which oral bacteria have been shown to modulate bacteria-host interactions?
How can antibiotics fail to penetrate biofilms effectively?
How can antibiotics fail to penetrate biofilms effectively?
What role does P.gingivalis play in relation to TLR4 in the presence of high iron concentrations?
What role does P.gingivalis play in relation to TLR4 in the presence of high iron concentrations?
What is the primary source of inorganic constituents in supragingival plaque?
What is the primary source of inorganic constituents in supragingival plaque?
What is the effect of P.gingivalis on interleukin-8 synthesis?
What is the effect of P.gingivalis on interleukin-8 synthesis?
How does P.gingivalis interfere with the complement system?
How does P.gingivalis interfere with the complement system?
Which of the following is NOT a step in the initial adhesion of bacteria during dental plaque formation?
Which of the following is NOT a step in the initial adhesion of bacteria during dental plaque formation?
What kind of material primarily composes the acquired pellicle?
What kind of material primarily composes the acquired pellicle?
What is the term used to describe the phenomenon where interspecies communication leads to an overgrowth of pathogenic microbiota?
What is the term used to describe the phenomenon where interspecies communication leads to an overgrowth of pathogenic microbiota?
What type of pathogens interact with keystone pathogens like P.gingivalis to affect the oral microbial community?
What type of pathogens interact with keystone pathogens like P.gingivalis to affect the oral microbial community?
How quickly does the acquired pellicle form on a tooth surface after brushing?
How quickly does the acquired pellicle form on a tooth surface after brushing?
What role do proteins with enzymatic activity in the acquired pellicle play?
What role do proteins with enzymatic activity in the acquired pellicle play?
Which component is NOT part of the acquired pellicle's composition?
Which component is NOT part of the acquired pellicle's composition?
What is the stability time for the acquired pellicle after it forms on the tooth surface?
What is the stability time for the acquired pellicle after it forms on the tooth surface?
What is the main function of acquired pellicle in relation to bacteria?
What is the main function of acquired pellicle in relation to bacteria?
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Study Notes
Dental Plaque Formation
- Acquired pellicle forms on the tooth surface within a minute after brushing or polishing
- It becomes stable within 2 hours, and fully matures in several hours.
- Composed of over 180 proteins, peptides, and glycoproteins, including keratins, mucins, proline-rich proteins, phosphoproteins, and histidine-rich proteins.
- Functions as adhesion sites for bacteria.
- Can be divided into two layers:
- Thin basal layer, very difficult to remove, forms permanently on teeth after eruption (dental cuticle)
- Thicker globular layer, up to 1 μm, easier to detach
- Initial Bacterial Adhesion: divided into three steps
- Transport to the surface: bacteria move to the tooth surface
- Reversible adhesion: bacteria attach to the tooth surface temporarily
- Permanent attachment: bacteria firmly attach to the tooth surface
- Secondary Colonization/Plaque Maturation: divided into two steps
- Co-adhesion/Coaggregation: different bacteria attach to each other.
- Plaque Maturation: the plaque becomes more complex and mature.
- Detachment: Bacteria detach from the plaque.
Composition of Supragingival Plaque
- Inorganic Components:
- Primarily calcium and phosphorus.
- Trace amounts of sodium, potassium, and fluoride.
- Source is primarily saliva.
- The accumulation of mineral content leads to the formation of calculus.
Factors Affecting Dental Plaque Formation
- Dysbiosis: an imbalance in the microbial community.
Microbial Complexes
- Research using DNA hybridization identified 40 subgingival microorganisms in 13,000 plaque samples.
- These microorganisms tend to group together in specific "complexes" associated with either health or disease.
Dental Biofilm Characteristics
- Biofilm: a complex community of microorganisms living on surfaces.
- Planktonic bacteria: free-floating bacteria.
- Biofilm bacteria: live within a matrix of extracellular materials.
- Differences in planktonic and biofilm bacteria:
- Metabolic Interactions: Biofilm bacteria interact metabolically, sharing resources and waste products.
- Antimicrobial Resistance: Biofilm bacteria are up to 1000 times more resistant to antimicrobials compared to their planktonic counterparts.
- Competition: Biofilm bacteria compete for resources by secreting antimicrobial molecules.
- Communication: Biofilm bacteria communicate via quorum sensing.
- Heterogeneity: Biofilms are comprised of various microenvironments.
- Structure: Biofilms contain microcolonies of bacterial cells, water channels, and steep chemical gradients.
- Quorum Sensing: bacterial communication via releasing, sensing, and responding to signal molecules.
- Example of Interactions: Interactions between S.gordonii and F.nucleatum influence the proteins produced by P.gingivalis.
- Differences in planktonic and biofilm bacteria:
Biofilm and Antimicrobial Resistance
- Reasons for Increased Resistance:
- Nutritional status
- Growth rate
- Temperature
- pH
- Prior exposure to sub-effective concentrations of antimicrobials.
- Slower growth rate of bacteria in a biofilm.
- Mechanisms of Resistance:
- Physical barrier: biofilms hinder antibiotic penetration.
- Chemical reactivity: biofilms remove charged or reactive antibiotics from solution.
- Enzymes: biofilm matrix may trap and concentrate enzymes that inactivate antibiotics.
- Multidrug Resistance Pumps: some biofilm bacteria have pumps that extrude antibiotics.
- DNA Exchange: antibiotic resistance can be spread within a biofilm via DNA exchange.
Keystone Pathogens
- Keystone Pathogens: bacteria that disproportionately influence the composition and behavior of the microbial community.
- P.gingivalis as a Keystone Pathogen:
- Manipulates TLR4 Response: can act as an agonist or antagonist of TLR4, depending on iron concentration.
- Inhibits Interleukin-8 Synthesis: interferes with immune response by inhibiting the synthesis of IL-8.
- Interferes with Complement System: suppresses complement activation and utilizes C5a to further its own survival.
Polymicrobial Synergy and Dysbiosis Model (PDS)
- PDS: suggests that interspecies communication between keystone pathogens and other bacteria (accessory pathogens) promotes the growth of pathogenic bacteria.
- Examples:
- P.gingivalis and A.actinomycetemcomitans interact with oral streptococci to influence the host immune response.
- Oral streptococci can attenuate the ability of F.nucleatum to stimulate IL-8 production.
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