Periodontal Disease Pathogen Hypotheses

Question 1

What is the non-specific plaque theory (Miller, 1890; Loesche, 1976; Theilade, 1986)?

Answer 1

-Dental infections caused by non-specific growth of of all bacteria in dental plaque

-Quantity of plaque determined the pathogenicity without discriminating between levels of virulence of bacteria

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Question 2

What can the non-specific plaque theory not explain?

Answer 2

The differences in the pathogenesis of periodontal diseases between different individuals.

Question 2

Why is the non-specific plaque theory still very important despite its disadvantages?

Answer 2

Because our current & conventional treatment of periodontal diseases is still based on this theory because conventional treatment highlights the importance of oral hygiene & root surface debridement.

Question 3

What is the specific plaque theory?

Answer 3

-Periodontal disease = presence of specific periodontal pathogens.

-Specifies the presence of these periodontal pathogens in dental plaque can definitely cause periodontal disease

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Question 4

What is the difference between gram -ve and gram +ve bacteria?

Answer 4

Gram +ve = Has thick peptidoglycan layer with cytoplasmic membrane at the bottom

Gram -Ve = very thin layer of peptidoglycan, cytoplasmic membrane, outer phospholipid membrane which has LPS (lipopolysaccharide).

LPS is one of the key virulence factors of periopathogenic bacterias that can cause bone resorption directly, and active the host immune response =inflammation

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Question 4

What figure did Socransky compile?

Answer 4

Bacteria that can be found in the mouth, divided into 5 complexes: In order of pathogenicity (least pathogenic to most ):

1.Yellow (gram +ve)
2.Green (gram +ve)
3.Purple
4.Orange (gram -ve)
5.Red (gram -ve)

Question 5

What was the problem with the specific plaque theory?

Answer 5

That the 3 bacteria in the red complex were also found in healthy mouths so it doesn’t necessarily mean that periodontal disease will be present if those bacteria are.

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Question 6

What is the ecological plaque theory?

Answer 6

• Periodontal disease is due to the imbalance of the total micro flora due to ecological stress, resulting in an enrichment of some oral pathogens

-Bacteria in dental plaque affect the environment.

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Question 7

What is the keystone pathogen theory?

Answer 7

• Indicates that certain low-abundance microbial pathogens can cause inflammatory disease by increasing the quantity of normal microbiota and by changing its composition.

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Question 7

Diagrammatically summarise the keystone pathogen theory.

Answer 7

1. Symbiotic microbiota in healthy sites live in harmony with the host.

2.Keystone pathogen is then introduced which causes impaired immunity and inflammation

3. Presence of keystone pathogens = Pathobionts becoming the dominant species
4. Overt inflammation
5. Periodontitis.

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Question 7

What is the Inflammation-Mediated Polymicrobial Emergence and Dysbiotic Exacerbation (IMPEDE) Model (Van Dyke, 2020)?

Answer 7

Highlights importance of inflammation.

If patient has gingivitis and host immune response/inflammation is successful, then gingivitis will not lead to periodontitis.

But if innate and adaptive immunity of host fails, periodontitis will occur.

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