Dental Plaque Flashcards
Define plaque
The community of microorganisms found on the tooth surface as biofilm embedded in a matrix of polymer of saliva and of bacterial origin
Describe plaque
Plaque is natural and it contribute to the host defences
It has properties beneficial to the host
Helps regulate the cardiovascular system
Dampens down immune response
What does the term biofilm mean?
Biofilm is a term to describe organism when they are attacked to a surface
In plaque the bacterial are combined with extra cellular proteins from the saliva and some that the bacteria may synthesis themselves
They are ubiquitous
Where is dental plaque often found?
In stagnent areas that are difficult to clean
These are the areas we get the most dental disease
Give an example of a biological biofilm
Dental plaque
What is the main characteristic of biofilms in a clinical situation?
Microorganisms growing on the surface as a biofilm are much less susceptible to antimicrobial agents (like antibiotics) than a suspension of the same micro organism free in liquid
How do biofilms form?
In a sequential order:
- Formation of conditioning film (this is a film of molecules that is absorbed from the envirmnemt that change the properties of the surface
- Transport of microbes
- Reversible phase
- Irreversible phase
- Secondary colonisation (co adhesion)
- Growth and matrix synthesis
- Detachment
How does dental biofilm (plaque form)
- Conditioning film forms on the tooth as the ACQUIRED PELLICLE
- Microbes are then transported to the surface by saliva
- Microbes may then be held there reversibly by electro chemical forces
- If the microbes are held there weekly then a more permeant irreversible phase begins. The organism then binds to the surface by intermolecular interactions between molecules on the bacterial surface (adhesin) to a complimentary receptor in the conditioning film (primary colonisation)
- This then leads to the attachment of a secondary coloniser to the primary coloniser. This is called adhesion over time this attachment leads to and increase in diversion and primary and secondary colonisers are in close proximity so share metabolic interactions and can change the environment making it more favourable for more organism
- Organisms then grow undergoing biofilm maturation and synthesises extra cellular polysaccharides
- Bacteria can sense there environment and if they think the environment isn’t favourable they will detach using the enzymic cleavage of adhesion
What happen to the teeth as soon as they erupt?
They are covered by a thin film of proteins derived from saliva
Bacteria then attaches to this film instead of the tooth itself
Describe the first stage of biofilm formation
Conditioning film begins to form
Conditioning film forms rapidally
Can be a micron in thickness
Most of the molecules derived from the saliva, gingival crevicular fluid and microbes
What is the conditioning film?
Conditioning film is a film of molecules that is absorbed from the envirmnemt that change the properties of the surface
Name some of the molecules that come from the host to make up the acquired pellicle during dental biofilm formation
Amylase (still functional despite being bound to a surface) Immunoglobulins Proline rich peptides (PRP) Mucins Statherin Agglutinins
Name some of the molecules that come from the bacteria to make up the acquired pellicle during dental biofilm formation
Glucosyltransferases
Glycans
Describe the second phase of dental biofilm formation
Transport of microbes
The bacterial are passively moved to the surface by the Flow of saliva
Describe the third phase of dental biofilm formation
Reversible phase
Bacteria will have small electrical charge and the surface will also have a small electrical charge on it
This results in the formation of electrostatic forces between to the 2 charges
This force is weak but can hold the bacteria near the surface allowing the interactions to become more specific
Describe the fourth phase of dental biofilm formation
Irreversible phase
colonisation
Interactions now become specific and over a shorter range
Interactions between molecules on microbial cells (adhesion) and receptors on the surface
This is A very specific interactions
Describe the fifth phase of dental biofilm formation
Secondary colonisation
Attachment of the secondary molecules to the primary coloniser
The secondary molecules don’t have. complimentary receptor to the bacteria in the biofilm but do have a complimentary receptor to the primary coloniser
This allows for the build quo of a more diverse community
What is the function of agglutinins
There function is to bind to microorganism while the are still in saliva, preventing the organism from attaching to the surface as we swallow them
What are cryptitopes?
They are hidden receptors for bacterial adhesion
What are adhesins?
Molecules on the surface of microbial cells that bind to complementary receptors
Which adhesin is found on the strepocuccus spp. bacteria and what is its corresponding receptor?
Adhesin: Antigen I/II
Receptor: Salivary agglutinin
Which adhesin is found on the mutans streptococci bacteria and what is its corresponding receptor?
Adhesin: Glucan binding protein
Receptor: Glucan
Which adhesin is found on the Actinomyces naeslundii bacteria and what is its corresponding receptor?
Adhesin: Type 1 fimbriae
Receptor: Proline rich proteins
Give an example of a molecule that has cryptotopes
Proline rich peptide
These peptides are circular and folded when in saliva and so the receptors for bacteria are hidden (cryptitopes)
When these molecules bind to a surface they unfold exposing the cryptitopes allowing bacteria to bind to the surface
Which bacterium do you see in the first few hour of biofilm formation?
Streptococci sanguinis
Streptococci oralis
Streptococci gordonii
Which organism plays a key role in the co adhesion stage of dental biofilm formation?
Gram negative Fusobacterium nucleatum
This organism will readily bind to any organism in the mouth especially early colonisers
Once attached to the early colonisers Fusobacteria will then allow for later colonisers to bind to it forming a complex and diverse environment of bacteria and micro organism
What are some characteristics of later colonisers
They are more demanding in their requirements
Usually they are strict anaerobes
What is the Fusobacterium nucleatum described as?
A riding molecules between early and late colonisers in oral biofilms
What happens as the biofilm begins to grow and mature?
The organism are in close contact and they start to communicate and interact
They can produce a range of signalling molecules that can diffuse out and tell other similar organism that this biofilm is a favourable place to inhabit
The organisms also begin to interact metabolically forming food chains
The organisms can change the environment eg the pH
They also form gradients and secrete the extraceullar matrix
Name the 5 things organism do as the biofilm begins to mature
- Cell to cell signalling occurs
- They interact metabolically
- They cane the environment slightly
- Form gradients
- Secrete the extracellular matrix