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MicroBiology Exam 2 > L5.Dental Plaque > Flashcards

L5.Dental Plaque Flashcards

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1
Q

What is the difference b/t intrinsic & extrinsic stains? Give an example of each

A

Intrinsic stains are deposited w/in the tooth such as a Tetracycline stain. Very difficult to remove.
Extrinsic stains are deposited on the tooth surface such as Chlorhexidine. Easily removed.

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2
Q

What is Materia Alba?

A

UNSTRUCTURED accumulation of bacteria, host cells and food debris. This type of deposit is LOOSELY attached to the teeth and is thus EASILY REMOVED with a blast from an air-water syringe.

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3
Q

What is dental plaque?

A

A highly STRUCTURED accumulation of bacteria and their extracellular products. Plaque is TIGHTLY ATTACHED to the surfaces of teeth and can only be removed mechanically.

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4
Q

What is Calculus?

A

Calculus = Tartar. Calcified dental plaque that is usually covered by a layer of uncalcified plaque b/c the rough surface of the calculus is easily bound by bacteria.

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5
Q

Does Calculus cause periodontal disease?

A

No. It provides a binding site for acidophiles that can’t normally bind teeth until specific glycoproteins are present in the acquired pellicle

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6
Q

T or F? The relative amounts, location, and color of plaque and calculus is identical from patient to patient.

A

False. Relative amount, location, color of dental plaque and calculus varies from individual to individual.

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7
Q

Why is plaque termed tenacious? Where does plaque form in the mouth?

A

Plaque is tenacious b/c it requires mechanical removal. Plaque accumulates on teeth, dental restorations & soft tissues of the oral cavity (basically anything that is not moving w/in the mouth).

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8
Q

What are the basic components of plaque?

A

Mainly bacteria, their products and to a lesser extent, entities derived from the host (mostly salivary molecules)

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9
Q

T or F? There is a variability in the pathogenicity of different types of plaque. i.e. certain are well tolerated by the host and others can cause caries and/or perio disease.

A

TRUE. Bacterial make-up of plaque is a key determinant of whether or not caries or perio disease will develope

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10
Q

Describe a bacteria in its Planktonic State?

A

It is a bacteria in solution.

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11
Q

Does the function of a bacterial cell differ when it is in its Planktonic State versus when it is in a Biofilm?

A

Yes, function varies greatly b/t planktonic and biofilm states for individual bacteria. Very important in disease!

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12
Q

While, especially at the start of biofilm formation, there are numerous distinct microenvironments w/in biofilms; why can’t you think of these biofilm microenvironments as isolated?

A

B/c Primitive Circulatory Systems in Biofilms carry nutrients and wastes b/t microenvironments. Meaning that products from reactions in one microenvironment will affect other microenvironments.

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13
Q

The interaction b/t S. gordonii & P. gingivalis provides P. gingivalis w/ what 2 advantages?

A
  1. Adhesion

2. Reduced oxygen (low redox potential)

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14
Q

The interaction b/t S. gordonii & F. nucleatum provides F. nucleatum w/ what 3 advantages?

A
  1. Adhesion
  2. low redox potential (reduced O2)
  3. Growth factors (Tricarboxylic & Fatty Acids)
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15
Q

The interaction b/t F. Nucleatum & T. forsythia provides T. forsythia w/ what advantage?

A
  1. Growth factors (e.g. N-acetylmuramic acid)
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16
Q

Give 3 reasons why inner layers of biofilms are more resistant to mechanisms of host defense & antibiotics?

A
  1. Inner layers of biofilm have more time to initiate stress response & many larger cells (such as macrophages) may not be able to penetrate to inner layer
  2. Outer layers of biofilm absorb much of the damage
  3. “persister” cells (those that are not dividing) may be present at a higher rate. These bacteria are not susceptible to penicillin b/c they are not dividing
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17
Q

What is communication b/t bacteria called?

A

Quorum Sensing

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18
Q

What is the main reason for quorum sensing? What may be an outcome that would explain why people w/ more plaque get caries & perio disease at a higher rate?

A

Quorum sensing is a process whereby small signaling molecules produced by bacteria are used by the cells to monitor the DENSITY of their population. Typically, results in altered gene expression and a subsequent change in bacterial “behavior” including Increased Virulence, which would explain why bacteria in people w/ more plaque cause more disease

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19
Q

Before plaque formation can begin, what is the absolutely essential first step?

A

The formation of a DENTAL PELLICLE

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20
Q

What are the 5 phases of plaque development?

A
  1. Development of the Acquired Pellicle
  2. Plaque initiation
  3. Growth
  4. Maturation
  5. Dispersal
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21
Q

Plaque formation is a HIGHLY ordered process. Does it give rise to a single or multiple distinct types of plaque?

A

Multiple distinct types of plaque, each of which exhibits a very organized structure

22
Q

Name at least 3 HOST Factor determinants of the Microbial Environment.

A
  1. Saliva
  2. Gingival crevicular fluid (GCF)
  3. Diet
  4. Oral hygiene habits
  5. Medical history/medications
23
Q

Name at least 3 BACTERIAL Factor determinants of the Microbial Environment.

A
  1. Adhesins
  2. Metabolic characteristics
    • O2 requirements
    • Preferred source of nutrients
  3. Production of Bacteriocins
  4. Coaggregation
  5. Factors affecting the host response
24
Q

If a single bacteria is resistant to a host defense will this affect the biofilm as a whole?

A

YES.

25
Q

Name at least 3 Local Physiochemical Factor determinants of the Microbial Environment.

A
  1. pH
  2. Redox potential (O2 potential)
  3. Temperature
  4. Nutrient availability
26
Q

How might swelling change the microbial environment of Gingival plaque?

A

When gingiva swells, the gingival margins move incisally, this results in the previously open plaque to be covered by gingiva. Will result in less O2 availability, decreased pH etc… leading to increased pathogenicity

27
Q

What is the acquired pellicle?

A

A CELL-FREE organic film that is deposited on teeth and is requisite for plaque formation.

28
Q

What are 4 components involved in the formation of the acquired pellicle?
What is the most important component?

A
  1. Salivary Gland proteins! GLYCOPROTEINS. MOST IMPORTANT
  2. Oral bacteria
  3. Oral mucosa
  4. Gingival crevicular fluid
29
Q

Following a total mouth cleaning how long does it take before the dental pellicle begins to reform? Full maturation?

A

Reformation begins almost immediately, w/in 2 hrs after tooth cleaning.
Takes up to 7 days for full maturation of dental pellicle.

30
Q

What are the 3 phases of bacterial attachment to dental pellicle? briefly describe each.
-What is required to complete the 3rd phase?

A
  1. Random Contact - Random bacteria bumping into teeth - no specificity
  2. Reversible adsorption - Involves weak attractive forces
  3. Firm attachment - Limited # of cell types that can form this - ADHESINS Required
31
Q

What are pioneer species?

A

Bacterial species that have adhesins that are capable of forming Firm Attachments (Irreversible Adsorption) to Enamel Receptors.

32
Q

What is the role of Extracellular Polysaccharides such as Glucan in the formation of dental pellicles?

A

Further reinforce attachments of bacterial species to the developing plaque matrix. Glucan specifically binds to glucan binding proteins on streptococcus mutans.

33
Q

T or F? Plaque initiation begins SUPRAGINGIVALLY

A

True

34
Q

Name the 5 REQUIRED Pioneer Species (Initial Colonizers) of the acquired pellicle

A
  1. Streptococcus sanguis
  2. Streptococcus gordonii
  3. Streptococcus oralis
  4. Streptococcus mitis
  5. Actinomyces naeslundii
35
Q

What type of bacteria are the 5 initial colonizers of the dental pellicle

A

They are all Gram positive, facultative cocci and rods that are well tolerated by the host.
The Streptococcus spp. are all Cocci
Actinomyces naeslundii is a Rod

36
Q

Describe plaque initiation from days (0-3)

A
  • Cell division leads to increased thickness and lateral spread of adherent bacteria.
  • Subsequently, competitive growth leads to the formation of columnar microcolonies composed of predominantly Coccoid cells.
  • Organic & inorganic components fill the ECM
37
Q

Name at least 3 organic and 2 inorganic components of the ECM in the developing plaque matrix

A

Organic
1. Salivary/serum proteins & glycoproteins
2. Lipids
3. DNA
4. Bacterial Polysaccharides (glucans & fructans) - can serve as nutrient source & binding sites for cariogenic bacteria.
Inorganic
1. Minerals (generally calcium & phosphorous)
-Supragingivally derived from saliva;
Subgingivally derived from GCF
2. Subgingivally, blood “products” (e.g. iron released from hemoglobin)

38
Q

Name 7 functions of ECM in developing plaque

A
  1. Adhesion to surface
  2. Mechanical stability
  3. Scaffold for 3-D structure
  4. Nutrient source
  5. Extracellular “digestive” system
  6. Reservoir of genes for Horizontal gene transfer (b/c DNA deposited throughout pellicle)
  7. Protection (from desiccation, oxidation, biocides, antibiotics & host defenses)
39
Q

What is the concept of Coaggregation? Where is it first seen in plaque formation?

A

Coaggregation is the adherence of genetically distinct bacterial organisms to one another mediated via specific interactions b/t molecules on their cell surfaces. This is seen first b/t Actinomyces species & streptococcal species (both Initial Colonizers)

40
Q

What are 4 benefits of coaggregation?

A
  1. Increase probability that species that need to interact (cooperativity) will do so
  2. Facilitate development of food chains
  3. Creation of environments needed for growth of particular species of bacteria (attachment of obligate anaerobes to O2-consuming species)
  4. Facilitate cell to cell signaling (Quorum Sensing!)
41
Q

In terms of coaggregation, why are Fusobacteria so important?

A

Fusobacteria have been found to coaggregate w/ the greatest range of species. Are believed to act as bridge from early & late colonizers.

42
Q

Early Supragingival Plaque are defined by what 4 characteristics?

A
  1. predominantly Gram + cocci & rods
  2. Tend to be Facultative anaerobes
  3. Organized as columnar microcolonies
  4. Generally well tolerated by host
43
Q

What 3 changes are taking place at the microenvironment at the tooth surface as plaque development progresses to day three?

A
  1. O2 availability Decreases
  2. Temperature Increases
  3. CHO (Nutrient) availability decreases
44
Q

Summarize the plaque maturation phase (day 3-60)

A
  • Increasing prevalence of Gram-positive & Gram-negative Rods & Filaments
  • Filaments, many of which are anaerobic, grow into coccoid plaque and eventually replace coccoid cells at tooth surface
45
Q

Env’t changes w/in the developing plaque drive a transition towards anaerobic microflora with the appearance of secondary (late) colonizers. Name the 6 secondary colonizers..

A
  1. Fusobacterium nucleatum
  2. Tannerella forsythensis
  3. Prevotella intermedia
  4. Porphyromonas gingivallis
  5. Treponema denticola
  6. Aggregatibacter actinomycetemcomitans
46
Q

Mature Supragingival Plaque (climax community) forms after what period of time?

A

3 weeks

47
Q

What 4 traits characterize Mature Supragingival Plaque communities?

A
  1. Contain a more equal mix of Gram + & Gram - organisms
  2. Contains cocci, rods, filaments & spirochetes
  3. Composed of both facultative anaerobes & anaerobes
  4. Associated w/ occurrence of dental caries & gingivitis!
48
Q

If left undisturbed, the plaque develops into what? How?

A

CALCULUS = Calcified Plaque Matrix. Forms when plaque seeded by mineralizing agents that lead it to develop into Calculus.

49
Q

Is calculus capable of causing disease? why is it so bad?

A

No. It is so bad b/c its rough surface provides a attachment site for cariogenic bacteria.

50
Q

How does the microenvironment change in the sagital suclus, as the gums swell and move incissaly, making previously supragingival plaque, into subgingival plaque. 3 things

A
  1. Decreased O2 availability
  2. Increased Temp
  3. Nutrients are derived from GCF and are PROTEINS instead of CHOs in saliva.
51
Q

What are 4 characteristics of the microbes that dominate the subgingival environment?

A
  1. Dominated by Gram - bacteria
  2. Dominated by anaerobic and capnophilic (like low O2, high CO2) organisms
  3. Composed mainly of proteolytic organisms (eat proteins)
  4. Associated w/ periodontitis
52
Q

Is dental plaque a static or dynamic process?

A

DYNAMIC. Responds to changes in environment

MicroBiology Exam 2 (6 decks)

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