46 Questions
What is the primary source of inorganic constituents in supragingival dental plaque?
Saliva
What is the function of glycoproteins and proline-rich proteins in the pellicle?
To serve as attachment sites for bacteria
What is the difference between adhesion and attachment of bacteria in dental plaque formation?
Adhesion is weak and reversible, while attachment is strong and irreversible
What is the purpose of co-adhesion in dental plaque formation?
To allow firmly attached primary colonizers to provide new receptors for attachment of other bacteria
What is the trend observed in the shift from facultative gram-positive to anaerobic gram-negative bacteria during dental plaque maturation?
From facultative gram-positive to anaerobic gram-negative
What is the primary source of organic constituents in dental plaque?
Saliva
How long does it take for colonization and plaque maturation to occur?
Within 24 to 48 hours
What is the function of the pellicle in dental plaque formation?
To provide attachment sites for bacteria
What type of forces are involved in the initial adhesion of bacteria to the pellicle?
Weak reversible Vander Waals and electrostatic forces
What is the primary source of inorganic constituents in subgingival dental plaque?
Gingival crevicular fluid
What type of plaque is located above the gingival margin?
Super gingival plaque
What type of bacteria are generally found in super gingival plaque?
Aerobic bacteria
What is the trend observed in the layers of plaque as it grows out from the tooth surface?
Gram positive to gram negative
What is unique about the sub gingival plaque compared to super gingival plaque?
Gram negative bacteria tend to accumulate both in the early and later layers
What is the difference between super gingival and sub gingival plaque?
Super gingival plaque is located above the gingival margin and sub gingival plaque is below
What type of bacteria thrive in the sub gingival region?
Anaerobic bacteria
What is the direction of plaque growth from the tooth surface?
From left to right
What is the characteristic of the early layers of plaque that are directly attached to the tooth?
Gram positive
What primarily consists of glycoproteins, purine-rich proteins, and inorganic molecules?
Pellicle
What type of bacteria are the primary early colonizers?
Streptococcus
What do secondary late colonizers tend to feed on?
Amino acids
What is the function of Fusobacterium?
Bridge between primary and secondary colonizers
What is the term for the communication among bacteria in the biofilm?
Quorum sensing
What is the benefit of quorum sensing in the biofilm?
Encourage the growth of beneficial species and discourage the growth of competing species
What is the characteristic of biofilm bacteria that makes them more resistant to antimicrobial agents?
Their ability to form a giant wall
What is the term for the fluid channels that run through the plaque mass?
Fluid channels
What is the term for the group of living microorganisms that includes the pellicle, primary colonizers, and secondary colonizers?
Biofaon
What is the characteristic of planktonic bacteria compared to biofilm bacteria?
They are less resistant to antimicrobial agents
What is the arrangement of microbe complexes in the image similar to?
The actual arrangement of bacterial species in the plaque
Which complexes are considered high priority for the board exam?
Red complex and its three bacteria
What is the red complex associated with?
Bleeding on probing and deep pocket depths
What is the purpose of the orange complex?
To support the sequential nature of plaque maturation
What is the name of the bacteria that causes gingivitis?
P Gingivalis
What is the ecological plaque hypothesis?
A theory that the mouth is an ecosystem, and bacteria and host factors influence the environment
What is the significance of the tooth surface in the image?
It is located on the left side of the image
Which of the following bacteria is NOT part of the red complex?
Fusobacterium nucleatum
What is the purpose of remembering the 'peas' and 'T's' in the red complex bacteria?
To remember the names of the bacteria in the red complex
What is the correct order of the plaque hypotheses?
Nonspecific, specific, ecological
Which bacterium causes aggressive periodontitis?
A. actinomycetemcomitans
Which bacterium is associated with healthy gingiva but can also cause root caries?
Actinomyces
Which of the following bacteria is a bridge microorganism?
F. nucleatum
Which bacterium is known to cause chronic periodontitis?
P. gingivalis
Which bacterium is associated with pregnancy gingivitis?
P. intermedia
Which bacterium is most commonly known to cause acute necrotizing form of either gingivitis or periodontitis?
T. denticola
Which bacterium is notorious for causing coronal caries?
S. mutans
Which bacterium is one of the most common oral bacteria and resides mostly on the tongue?
S. salivarius
Study Notes
Plaque Composition
- Two main types of plaque regions: Supragingival (above the gingival margin) and Subgingival (below the gingival margin)
- Supragingival plaque:
- Bacteria are generally aerobic
- Early layers of plaque tend to be Gram-positive
- Outer layers tend to be Gram-negative
- Subgingival plaque:
- Bacteria are generally anaerobic
- Gram-negative bacteria tend to accumulate in both early and later layers
- Gram-positive bacteria are present in early layers, but decrease in later layers
Plaque Formation
- Initial step: Formation of pellicle within seconds of tooth cleaning
- Consists of glycoproteins, proline-rich proteins, and other molecules that serve as attachment sites for bacteria
- Not harmful by itself, but provides attachment sites for bacteria
- Second step: Adhesion and attachment of bacteria within minutes
- Initial adhesion is weak and reversible, due to Vander Waals and electrostatic forces
- Firm attachment is strong and irreversible, due to specific bacterial adhesion molecules and receptors provided by pellicle
- Third step: Colonization and plaque maturation within 24-48 hours
- Firmly attached primary colonizers provide new receptors for attachment of other bacteria
- Shift from Gram-positive to Gram-negative bacteria as plaque grows and matures
Plaque Maturity
- Mature plaque is a biofilm, consisting of fluid channels that permit passage of nutrients and waste products
- Quorum sensing: communication among bacteria in biofilm to encourage growth of beneficial species and discourage growth of competing species
- Biofilm bacteria are more resistant to antimicrobials than planktonic bacteria
Microbial Complexes
- Different colors and names are associated with different microbial complexes (e.g. blue complex, yellow complex, orange complex, red complex)
- Red complex bacteria (P. gingivalis, T. denticola, and T. forsythia) are associated with periodontal disease and are important to know for the board exam
- Orange complex bacteria (F. nucleatum, P. intermedia, and S. rectus) precede the presence of red complex bacteria and support the sequential nature of plaque maturation
Major Bacteria to Know
- Aggregatibacter actinomycetemcomitans (Aa): causes aggressive periodontitis
- P. gingivalis: causes chronic periodontitis
- T. denticola: causes acute necrotizing gingivitis or periodontitis
- T. forsythia: associated with periodontal disease
- P. intermedia: influences pregnancy gingivitis
- F. nucleatum: orange complex bacteria, bridge microorganism
- Actinomyces: associated with healthy gingiva, can cause root caries
- S. mutans: notorious for causing coronal caries
- S. salivarius: one of the most common oral bacteria, resides mostly on the tongue
Learn about the composition of dental plaque, including the two main types of plaque regions, supragingival and subgingival, and the characteristics of bacteria in each region.
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