Aetiology and Pathogenesis Flashcards
What does clinical periodontal health require
A health promoting biofilm within which symbiotic relationships exist between microorganisms and with the host response
What does the host response provide to the biofilm in clinical health
Key nutrients via GCF
What happens if the biofilm is not disrupted frequently and is allowed to accumulate
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)
What can developing dysbiosis trigger in susceptible patients
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
What do local plaque retention factors do
make you more likely to get gingivitis as an accumulation of plaque causes gingivitis
What are examples of plaque retention factors
- Calculus
- Restoration margins
- Crowding
- Mouth breathing
What does mouth breathing do that results in plaque retention
interferes with saliva
What are examples of systemic modifying factors that can also impact the route to clinical disease
- Sex hormones
* Medication
What are signs of gingival health
- Knife edge, scalloped gingival margin
- Stippling (in about 30%)
- Pink
In gingival health what is the intact barrier provided by
junctional epithelium
it is non ulcerated
What is the turnover of the intact barrier
very quick
4-5 day turnover
What is the turnover of the intact barrier referred to as
epithelial cell shedding
What is the advantage of epithelial cell shedding
makes invading difficult due to this continuous shedding
What is the cellular response present in health
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.
What occurs in gingivitis
altered microbial colonization
What is the appearance of the gingiva in gingivitis
now red and inflamed with a shiny appearance clinically
What happens as a result of gingivitis
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.
In disease what kind of bacteria is it shifted to
gram positive aerobes
What happens in periodontitis
In periodontitis there is apical migration of the junctional epithelium
There is bone loss
Plasma cells constitute more than 50%
what happens in a false pocket
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
What is the progression of attachment loss once periodontitis has been initiated
may be episodic rather than continuous
What is the progression of attachment loss usually
0.05-0.1mm a year
What is a biofilm
A biofilm is one or more communities of microorganisms embedded in a glycocalyx attached to a solid surface
what are the properties of a biofilm
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
Describe bacteria virulence
The bacteria have the ability to colonise and compete in an ecological niche
What are the different ways bacteria can evade host defenses
- Degrading host immunoglobulin and complement
- Leucotoxin production
- Tissue invasion
- Inhibition of antibody synthesis
What is the evidence for specific bacterial causation
- 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
What are the bacteria in the strongest associated complex
p. gingival
b. forsythus
t. denticola
What are some of the bacteria in the second strongest associated complex
f. nuc. polymorphum
p. intermedia
p. micros
what is the model of oral biofilm formation
Those at the bottom are the early colonisers – as the biofilm accumulates it allows for other bacteria to come in and attach
what is the keystone pathogen in periodontitis
p. gingivalis
what does the presence of the keystone pathogen do
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.
what are the host response mechanisms
saliva
epithelium
GCF
inflammatory response and immune responses
how does epithelium act as a immune response
o Physical barrier
o Shedding of cells
o Production of inflammatory mediators
how do neutrophils help in the immune response
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
describe how we go from health to periodontitis
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
what is the initial periodontal lesion composed of
mainly T lymphocytes (CD4) which generate cytokines and summon other cells to come in
what cells predominate in the later stage
b cells and plasma cells
what is produced locally in periodontitis
antibodies
what are the functions of antibodies
- 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
what are MMPs
MMPs are a family of zinc and calcium dependent proteolytic enzymes, which include collagenases
what is matrix degradation in periodontitis due to
matrix degradation is largely a result of MMPs secreted by host inflammatory cells.
what do MMPs do
break down connective tissue which is key to the progression
what is bone loss caused by
The other part of the periodontitis is bone loss which is caused by osteoclast activation
describe how osteoclast activation occurs
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
how much bone loss is there usually
1-2mm
what is horizontal bone loss
bone resorbs at the same level
what is vertical bone loss
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.
why do we get different patterns of bone loss
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
what are general risk factors for periodontitis
- Smoking
- Diabetes
- Stress
- Drugs
- Systemic disease
- Nutrition
what are general risk determinants for periodontitis
- Genetics
- Socioeconomic status
- Gender
what are the local risk factors
anatomical
tooth position
iatrogenic
what are anatomical risk factors
o Enamel pearls/projections
o Grooves
o Furcation
o Gingival recession
what are tooth position risk factors
o Malalignment o Crowding o Tipping o Migration o Occlusal forces
what are iatrogenic risk factors
o Restoration overhangs
o Defective crown marginas
o Poorly designed partial dentures
o Orthodontic appliances
what is the key risk factor
smoking
what are the effects of smoking
- 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
what is the primary etiological agent in inflammatory periodontal disease
plaque
what is the extent and severity of disease dependent on
interaction between microbe and host
what conveys supectibility
risk factors which interfere with host defenses
In clinical periodontal health, what does the biofilm release and what is its effect on the host response?
The various proteins and peptides released by the biofilm organisms trigger a host response that is both proportionate and resolving
What does dysbiosis refer to
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.
