Aetiology and Pathogenesis

Question 1

What does clinical periodontal health require

Answer 1

A health promoting biofilm within which symbiotic relationships exist between microorganisms and with the host response

Question 2

What does the host response provide to the biofilm in clinical health

Answer 2

Key nutrients via GCF

Question 3

What happens if the biofilm is not disrupted frequently and is allowed to accumulate

Answer 3

The conditions within it start to favour bacterial species that are capable of sensing and influencing their environment by employing chemical cues.

These organisms triggers stronger host response, which, can lead to the development of gingival inflammation and increase the supply of nutrients that encourage the proliferation of traditional pathogens (e.g p. gingivalis)

Question 4

What can developing dysbiosis trigger in susceptible patients

Answer 4

An inappropriate and frequently excessive host response in which excess cytokines, ROS and MMPs are generated resulting in periodontal tissue damage.

DAMPs are released which further propagate the inflammatory response and failure of innate inflammation resolving mechanisms results in chronic inflammation

Question 5

What do local plaque retention factors do

Answer 5

make you more likely to get gingivitis as an accumulation of plaque causes gingivitis

Question 6

What are examples of plaque retention factors

Answer 6

• Calculus
• Restoration margins
• Crowding
• Mouth breathing

Question 7

What does mouth breathing do that results in plaque retention

Answer 7

interferes with saliva

Question 8

What are examples of systemic modifying factors that can also impact the route to clinical disease

Answer 8

• Sex hormones

* Medication

Question 9

What are signs of gingival health

Answer 9

• Knife edge, scalloped gingival margin
• Stippling (in about 30%)
• Pink

Question 10

In gingival health what is the intact barrier provided by

Answer 10

junctional epithelium

it is non ulcerated

Question 11

What is the turnover of the intact barrier

Answer 11

very quick

4-5 day turnover

Question 12

What is the turnover of the intact barrier referred to as

Answer 12

epithelial cell shedding

Question 13

What is the advantage of epithelial cell shedding

Answer 13

makes invading difficult due to this continuous shedding

Question 14

What is the cellular response present in health

Answer 14

There are neutrophils that are finding their way to the gingiva, keeping the environment under control with the help of lymphocytes.

There is a flow of gingival crevicular fluid that contains antibodies.

There is phagocyte function and lymphocyte infiltrate as well as complement activity.

The key to the immune response in health is it is regulated.

Question 15

What occurs in gingivitis

Answer 15

altered microbial colonization

Question 16

What is the appearance of the gingiva in gingivitis

Answer 16

now red and inflamed with a shiny appearance clinically

Question 17

What happens as a result of gingivitis

Answer 17

Increased flow of GCF with an influx of neutrophils, increased lymphocytes and monocytes.

There is plasma cell infiltrate as well as proliferation and ulceration of epithelium – the ulceration is what causes the bleeding.

Question 18

In disease what kind of bacteria is it shifted to

Answer 18

gram positive aerobes

Question 19

What happens in periodontitis

Answer 19

In periodontitis there is apical migration of the junctional epithelium
There is bone loss
Plasma cells constitute more than 50%

Question 20

what happens in a false pocket

Answer 20

In a false pocket, bone is still intact. The junctional epithelium has not changed position, it has just become ulcerated and the rest of the epithelium has started to proliferate creating a pocket

Question 21

What is the progression of attachment loss once periodontitis has been initiated

Answer 21

may be episodic rather than continuous

Question 22

What is the progression of attachment loss usually

Answer 22

0.05-0.1mm a year

Question 23

What is a biofilm

Answer 23

A biofilm is one or more communities of microorganisms embedded in a glycocalyx attached to a solid surface

Question 24

what are the properties of a biofilm

Answer 24

Biofilms provide protection for colonizing species from competing organisms and environment (host defenses, antibiotics etc)
They facilitate the uptake of nutrients and removal of metabolic products
Development of appropriate physiochemical environment e.g pH, O2 concentration
It allows for communication between bacteria

Question 25

Describe bacteria virulence

Answer 25

The bacteria have the ability to colonise and compete in an ecological niche

Question 26

What are the different ways bacteria can evade host defenses

Answer 26

* Degrading host immunoglobulin and complement * Leucotoxin production * Tissue invasion * Inhibition of antibody synthesis

Question 27

What is the evidence for specific bacterial causation

Answer 27

* Presence in elevated numbers at diseased sites * Reduced numbers following periodontal therapy * Presence of an elevated specific immune response * Production of virulence factors (which is what allows them to cause disease) * Evidence from animal models

Question 28

What are the bacteria in the strongest associated complex

Answer 28

p. gingival b. forsythus t. denticola

Question 29

What are some of the bacteria in the second strongest associated complex

Answer 29

f. nuc. polymorphum p. intermedia p. micros

Question 30

what is the model of oral biofilm formation

Answer 30

Those at the bottom are the early colonisers – as the biofilm accumulates it allows for other bacteria to come in and attach

Question 31

what is the keystone pathogen in periodontitis

Answer 31

p. gingivalis

Question 32

what does the presence of the keystone pathogen do

Answer 32

Their presence in the biofilm will change it and they will use bacteria that were previously friendly and use them as allies to create a dysbiotic biofilm resulting in an inflammatory response. The bacteria like the inflammation because the environment suits them.

Question 33

what are the host response mechanisms

Answer 33

saliva epithelium GCF inflammatory response and immune responses

Question 34

how does epithelium act as a immune response

Answer 34

o Physical barrier o Shedding of cells o Production of inflammatory mediators

Question 35

how do neutrophils help in the immune response

Answer 35

 Generate reactive oxygen species that kill bacteria but also cause bistandard damage to the host  Extracellular traps – neutrophil explodes into a web of sticky DNA and other molecules allowing it to trap bacteria. In doing so it releases mediators that kill bacteria but also damage the host  They are found in health also but the numbers are lower

Question 36

describe how we go from health to periodontitis

Answer 36

The normal flora turn into a dysbiotic biofilm and this results in an inflammatory response including neutrophils. For some patients this can contain the disease meaning they will have gingivitis without progression. For the vast majority it results in the evolution of the pathogenic biofilm and will progress to periodontitis

Question 37

what is the initial periodontal lesion composed of

Answer 37

mainly T lymphocytes (CD4) which generate cytokines and summon other cells to come in

Question 38

what cells predominate in the later stage

Answer 38

b cells and plasma cells

Question 39

what is produced locally in periodontitis

Answer 39

antibodies

Question 40

what are the functions of antibodies

Answer 40

* Complement activation * Neutralization of toxins * Opsonization and phagocytosis * Prevents progression infection and therefore potentially serious systemic consequences * Inadvertent local tissue damage (bystander damage) combined with attempts at repair

Question 41

what are MMPs

Answer 41

MMPs are a family of zinc and calcium dependent proteolytic enzymes, which include collagenases

Question 42

what is matrix degradation in periodontitis due to

Answer 42

matrix degradation is largely a result of MMPs secreted by host inflammatory cells.

Question 43

what do MMPs do

Answer 43

break down connective tissue which is key to the progression

Question 44

what is bone loss caused by

Answer 44

The other part of the periodontitis is bone loss which is caused by osteoclast activation

Question 45

describe how osteoclast activation occurs

Answer 45

When the host immune response is excessive for long periods it will promote production of osteoclasts and promote bone loss. Cytokines e.g tnf will cause osteoclasts to activate and resorb bone

Question 46

how much bone loss is there usually

Answer 46

1-2mm

Question 47

what is horizontal bone loss

Answer 47

bone resorbs at the same level

Question 48

what is vertical bone loss

Answer 48

one side of the bone level is higher than the other. In angular bone loss there may be possibility to regenerate the bone because of the wall of bone on one side of it so sometimes we can use that bone to help it regenerate. There is no chance of regeneration in horizontal bone loss.

Question 49

why do we get different patterns of bone loss

Answer 49

The reason why we get different patterns is presumed to be down to the shape of the bone to begin with. If the bone is quite narrow you will get horizontal bone loss as the zone of destruction form the most apical point of plaque. If it is wider than it will be vertical bone loss

Question 50

what are general risk factors for periodontitis

Answer 50

* Smoking * Diabetes * Stress * Drugs * Systemic disease * Nutrition

Question 51

what are general risk determinants for periodontitis

Answer 51

* Genetics * Socioeconomic status * Gender

Question 52

what are the local risk factors

Answer 52

anatomical tooth position iatrogenic

Question 53

what are anatomical risk factors

Answer 53

o Enamel pearls/projections o Grooves o Furcation o Gingival recession

Question 54

what are tooth position risk factors

Answer 54

``` o Malalignment o Crowding o Tipping o Migration o Occlusal forces ```

Question 55

what are iatrogenic risk factors

Answer 55

o Restoration overhangs o Defective crown marginas o Poorly designed partial dentures o Orthodontic appliances

Question 56

what is the key risk factor

Answer 56

smoking

Question 57

what are the effects of smoking

Answer 57

* Effect on subgingival plaque is uncertain * Vasoconstriction of gingival vessels and increased gingival keratinization * Impaired antibody production * Depressed numbers of Th lymphocytes * Impaired PMN function * Increased production of proinflammatory cytokines

Question 58

what is the primary etiological agent in inflammatory periodontal disease

Answer 58

plaque

Question 59

what is the extent and severity of disease dependent on

Answer 59

interaction between microbe and host

Question 60

what conveys supectibility

Answer 60

risk factors which interfere with host defenses

Question 61

In clinical periodontal health, what does the biofilm release and what is its effect on the host response?

Answer 61

The various proteins and peptides released by the biofilm organisms trigger a host response that is both proportionate and resolving

Question 62

What does dysbiosis refer to

Answer 62

The concept that some diseases are due to a decrease in the number of beneficial symbionts and an increase in the number of pathogens Simultaneously, a succession of microbial complexes develops.