Dental Biofilm (Plaque) Formation

Question 1

What can you group the normal microflora in the oral cavity into?

Answer 1

3 groups:

Indigenous species (resident oral microflora)- almost always present in stable relationship with the host and don’t compromise the survival of the host

Supplemental species- present in small numbers but if the environment changes can become more abundant e.g. lactobacilli, P. gingivalis, S. mutans

Transient flora- pass through but do not become established e.g. E. coli

Question 2

What are the 4 stages in plaque formation?

Answer 2

-Acquired pellicle formation
-Pioneer microbial colonisers
-Co-aggregation
-Maturation

Question 3

What happens in the acquired pellicle formation stage of plaque formation?

Answer 3

-Bacteria cannot attach onto the clean enamel surface but saliva is rich in glycoproteins, phosphoproteins & lipids that can attach onto the clean enamel surface

-Enamel surface is negitvely charged due to the (-ve) charged phosphate groups of calcium hydroxyapatite

So the first stage of plaque formation is the attachment of +vely charged glycoproteins, phosphoproteins or lipids to the -vely charged clean enamel surface

Question 4

What are the first proteins that form the acquired dental pellicle called?

Answer 4

Proline-rich proteins & statherin

Question 5

What happens in the second stage of dental plaque formation?

Answer 5

Once the acquired pellicle has been established, some of the pioneer microbial colonisers can now attach onto the pellicle

Once they are firmly attached, they start to divide & produce EPS which provide a scaffold for the formation of dental biofilm

Question 5

When does acquired pellicle formation occur?

Answer 5

Minutes after brushing your teeth

Question 6

What are some examples of pioneer microbial colonisers?

Answer 6

-Streptococcus sanguinis, S. oralis, S. mitis (IgA1 protease)

-Actinomyces spp.

-Haemophilus spp.

-Neisseria spp.

Question 6

Why is sucrose important?

Answer 6

It is crucial for Extracellular polysaccharide production (EPS).

Glucan is the first most important (EPS) and then its fructan

Question 7

What happens in the established dental biofilm?

Answer 7

Microbial succession & syntrophism (cross-feeding).

Question 8

What are the beneficial and antagonistic microbial interactions in dental plaque formation?

Answer 8

look at slides

Question 9

What happens in co-aggregation?

Answer 9

Plaque microflora becomes more diverse

Alteration of local environment by initial colonisers (receptors, nutrients, fermentation products, CO2)

Leads to attachment of late colonisers such as:

-Fusobacterium nucleatum (bridging species-adhesins), Veillonella spp, Eubacterium spp, Porphyromonas gingivalis, Prevotella intermedia, Treponema spp.

Question 10

When does maturation of dental biofilm happen?

Answer 10

Around 7-10 days after acquired pellicle formation.

Question 10

What happens in the maturation stage of dental biofilm formation?

Answer 10

Growth rate slows down

Continuous production of EPS (leads to structural integrity, tolerance to environmental factors & antimicrobials)

Coordination of activities, vertical & horizontal stratification

Shear forces limit further expansio

Question 11

What is materia alba?

Answer 11

Materia Alba refers to soft accumulations of bacteria, tissue cells and food particles that lack the organised structure of dental plaque

It’s loosely attached to the tooth surface and soft oral tissues

Easily displaced with fluid flow (water)