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Periodontics > Microbiology of Periodontal Disease > Flashcards

Microbiology of Periodontal Disease Flashcards

1
Q

What is dental plaque?

A

Structured, resilient yellow substance which adheres tenaciously to intraoral hard surfaces, including removable and fixed appliances and restorations

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2
Q

Describe the steps from clean surface to plaque formation

A
  • Clean tooth surface
  • Salivary glycoprotein coat
  • Bacterial colonisation
  • Initially gram positive cocci and after few hours the plaque bulk increases
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3
Q

Describe plaque maturation

A
  • Gram positive bacteria gradually replaced by Gram negative species
  • Gram negative filamentous forms e.g fusiforms and spirochaetes appear in later stages
  • Dental plaque is composed of 80-89% water
  • Calcified plaque is known as calculus
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4
Q

Give 2 reasons disclosing solution may be useful for patients who do not brush their teeth regularly

A
  1. Unstained plaque may not be readily apparent

2. Extent of plaque becomes apparent when stained with disclosing solution

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5
Q

Describe supragingival plaque

A
  • 50% matrix
  • Mostly gram positive aerobic bacteria unless bulk increases
  • Will extend under gingival margin if undisturbed
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6
Q

What is the subgingival region between root and sulcular epithelium called?

A

Gingival sulcus (deepens to the periodontal pocket in periodontitis)

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7
Q

Describe subgingival plaque

A
  • Subgingival region less oxygenated so favours growth of anaerobes
  • Subgingival plaque contains little to no matrix
  • Mostly contains gram negative rods and spirochetes
  • Majority of periodontal pathogens found in subgingival plaque
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8
Q

Describe 4 regions of the mouth where early plaque formation occurs faster

A
  1. Molar areas
  2. Buccal tooth surfaces (compared with oral sites)
  3. Lower jaw compared to upper jaw
  4. Interdental regions (compared with buccal or oral surfaces)
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9
Q

Describe periodontal disease

A
  • Homeostatic mechanisms which provide stability in commensal community
  • Environmental modification e.g inflammation/immune suppression/reduced salivary flow etc.
  • Disease community becomes to form due to overgrowth of pathogens
  • Disease community causes periodontal diseases
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10
Q

Name 2 out-dated hypotheses of plaque and periodontal disease which do not fit with periodontal disease

A
  1. Specific Plaque Hypotheses - Only a few microorganisms in plaque are actively involved in disease
  2. Non-Specific Plaque Hypotheses - Outcome of overall activity of total plaque microflora
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11
Q

What is the correct hypotheses on plaque and periodontal disease?

A

Ecological Plaque Hypothesis

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12
Q

Describe the Ecological Plaque Hypothesis for the development of periodontal disease

A
  • Organisms associated with disease may be found at healthy sites but at levels too low to be clinically relevant
  • Disease occurs due to shift in balance of resident microflora due to change in local environmental conditions
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13
Q

Give 3 examples of how Ecological Plaque Hypothesis says periodontal disease can be prevented

A
  1. Targeting putative pathogens
  2. Reducing severity of inflammatory response
  3. Altering redox potential of pocket to prevent growth of obligate anaerobes
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14
Q

Describe Socransky’s colour coded bacteria system

A
  • Red complex found most frequently in deep periodontal pockets
  • Red complexes usually preceded by members of orange complex
  • Members of yellow, green and purple complexes generally associated with healthy sites
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15
Q

Name 3 microorganisms found in Socransky’s “red” group

A
  1. P. gingivalis
  2. T. forsythia
  3. T. denticola
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16
Q

Name 4 microorganisms found in Socransky’s “orange” group

A
  1. P. intermedia
  2. P. nigrescens
  3. P. micros
  4. F. nucleatum
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17
Q

Name 3 microorganisms found in Socransky’s “yellow” group

A
  1. S. oralis
  2. S. mitis
  3. S. intermedius
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18
Q

Name 2 microorganisms found in Socransky’s “purple” group

A
  1. V. parvula

2. A. odontolyticus

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19
Q

Name 3 microorganisms found in Socransky’s “green” group

A
  1. C. gingivalis
  2. E. corrodens
  3. C. concisus
20
Q

Describe the shift from health to gingivitis to periodontitis in terms of pocket depth and attachment

A

Health - Normal pocket depth, full attachment
Gingivitis - Increased pocket depth, full attachment
Periodontitis - Increased pocket depth, attachment loss

21
Q

Describe 6 species of microorganisms found in the periodontal pocket during periodontal health

A 
Streptococci (oralis, mitis, sanguinis)
Actinomyes
Vellonella
Haemophilus
Neisseria
Fusobacteria
22
Q

Describe 4 microorganism species found in the periodontal pocket during gingivitis

A
  1. Actinomyces
  2. Prevotella intermedia
  3. Bacteroides
  4. Fusobacterium nucleatum
23
Q

Describe 5 microorganisms found in the periodontal pocket during periodontitis

A
  1. Porphyromonas gingivalis
  2. Treponema denticola
  3. Prevotella intermedia
  4. Fusobacterium nucleatum
  5. Tannerella forsythia
24
Q

Describe the aetiology of gingivitis

A
  • Accumulation of dental plaque
  • Reversed by plaque removal
  • Exacerbated by systemic factors e.g pregnancy / puberty
  • Gingival inflammation
25
Q

Describe the aetiology of periodontitis

A
  1. Colonisation of subgingival regions by specific groups of microorganisms
  2. Expression of virulence factors e.g leukotoxin
  3. Destructive immune responses
  4. Loss of periodontal tissue including gingiva, periodontal ligament and alveolar bone
26
Q

Describe how plaque bacteria cause disease

A
  • Majority of bacteria are commensal and can be removed with good oral hygeine technique
  • Red and orange complex organisms produce virulence factors which initiate periodontal disease and allow progression
  • Bacteria do not need to invade tissues in order to cause disease (only exceptions are bacteria associated with severe disease e.g ANUG)
  • Immune status and effectiveness of host response are key determinants of disease susceptibiltiy
27
Q

What is virulence?

A

Relative measure of the damage induced by the microorganism

28
Q

What are virulence factors?

A

Microbial determinants that mediate host damage in the context of microbial pathology

29
Q

Name 5 examples of surface associated virulence factors

A
  1. Adhesion pili
  2. Capsule
  3. LPS
  4. Flagella
  5. Surface proteins
30
Q

Name 3 secreted virulence factors

A
  1. Exotoxin
  2. Enzymes
  3. Iron binding proteins
31
Q

Describe how bacteria can acquire virulence genes

A

By phages via transduction and other mobile genetic elements such as plasmids via conjugation

32
Q

Name 2 virulence factors with direct toxic effects

A
  1. Endotoxin

2. Exotoxin

33
Q

Describe endotoxin as a virulence factor

A
  • Bacterial endotoxin is produced by all Gram negative bacteria
  • Principally consist of LPS
  • LPS is released from bacterial cell wall during growth and after lysis
  • LPS is potent toxin capable of activating complement macrophages, degranulating neutrophils and stimulating bone resorption
34
Q

Describe exotoxin as a virulence factor

A
  • Exotoxins are continuously released by certain live bacteria
  • Leukotoxin produced by A. actinomycetemcomitans inhibits neutrophils and macrophages
35
Q

Describe adhesins as a virulence factors

A
  • Microbial components which enable microbe to attach to host tissues
  • Diverse molecules which include proteins, polysaccharides and cell wall components
36
Q

Describe polysaccharide capsules as a virulence factors

A
  • Required for virulence in mammalian hosts
  • Most capsules function by protecting microbe from host immune mechanisms
  • Can serve as adhesins
37
Q

Describe enzymes as a virulence factor

A
  • Include proteases, glucosidases and phospholipases
  • Damage cells and provide nutrients which can be assimilated by microbes
  • Each bacterium contains different enzymes
  • F. nucleatum does not produce proteolytic enzymes but acts as key bridging organism for periodontal pathogens such as P. gingivalis
38
Q

Describe Porphyromonas gingivalis as a red complex organism in periodontal disease aetiology

A
  • Strictly anaerobic
  • Often isolated from sub-gingival sites especially in advanced periodontitis
  • Strongly associated with adult periodontitis
  • Virulence factors include capsule and production of proteases which degrade complement, immunoglobulins and collagen
39
Q

Describe Tanerella forsythia as a red complex organism in periodontal disease aetiology

A
  • Implicated in the clinical attachment loss associated with periodontitis
  • Virulence factors include production of trypsin-like proteases and glycosidase enzymes
40
Q

Describe Treponema denticola as a red complex organism in periodontal disease aetiology

A
  • Found close to junctional epithelium in periodontal pocket
  • Adhere to host cells and tissues as well as to matrix proteins
  • Virulence factors include production of potent hydrolytic enzymes including collagenases and proteases
41
Q

Describe Prevotella species as an orange complex organism in periodontal disease aetiology

A
  • Strictly anaerobic
  • P. intermedia and P. nigrescens are black pigmented strains
  • P. intermedia associated with disease while P. nigrescens isolated from healthy sites
  • P. intermedia virulence factors include LPS production and ability to resist phagocytosis
42
Q

Describe Fusobacterium species as an orange complex organism in periodontal disease aetiology

A
  • F. nucleatum is an obligate anaerobe
  • Fusobacteria able to aggregate with most other oral bacteria so are considered bridging organism between early and late colonisers
  • Virulence factors of F. nucleatum include production of potent LPS and butyric acid
  • F. nucleatum is unable to produce hydrolytic enzymes
43
Q

Describe Aggregatibacter actinomycetemcomitans as an organism in periodontal disease aetiology

A
  • Not colour coded by Socransky
  • Implicated in aggressive form of periodontal disease in adolescents
  • Associated with actively progressing lesions
  • Virulence factors include production of collagenase and ability to resist phagocytosis
44
Q

Describe 4 bacterial interactions and pathogenic synergy in the aetiology of periodontal disease

A
  1. Signal each other and relay information about biofilm environment
  2. Gene transfer can occur readily in biofilms e.g antibiotic resistant genes
  3. Co-adhesion allows organisation of biofilm architecture
  4. Extracellular polymeric matrix within the biofilm is protective
45
Q

Describe how pathogens lead to tissue destruction

A
  • LPS activates complement and macrophages, degranulates neutrophils and directly stimulates bone resorption
  • Leukocidin release by A. actinomycetemcomitans destroys or lyses white blood cells
  • Collagenases break down host proteins
  • Innate and adaptive immune responses are elicited and magnitude determine whether bacteria are eliminates or bystander damage occurs

Periodontics (8 decks)

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