L4: Biochemical events in dental plaque

Question 1

What is the main causing factor of dental caries?

Answer 1

Bacteria produces acid & leads to demineralisation = cavities

Question 2

What is dental plaque?

Answer 2

Aggregation of bacteria and products onto the tooth surface

Question 3

What is the composition of dental plaque?

Answer 3

1) Water - 80%
2) Solid - 20%
3) Bacterial and Salivary protein - 50%
4) Carbohydrates and lipids - 20%-30%
5) Inorganic components

Question 4

flip for some funfacts on extra and intracellular polysaccharides (carbs and lipids in dental plaque)

Answer 4

• Synthesized by bacteria
• Bacterial attachment and cohesion
• Reservoir of fermentable substrates

Question 5

what inorganic components are found in dental plaque?

Answer 5

Ca, P, K, Na, Mg, F

Most Ca is non-ionic, becomes ionized as pH drops Determine rates of enamel dissolution and remineralization

Question 6

what is plaque fluid?

Answer 6

the extracellular aqueous phase of dental plaque

Question 7

What is rested plaque fluid?

Answer 7

Composition of plaque one to several hours after eating

Question 8

What is starved plaque fluid?

Answer 8

Composition of plaque following overnight fasting

Question 9

What is the main acid involved in caries formation?

Answer 9

Lactic acid

Question 10

What is the stephan curve?

Answer 10

a model of how plaque bacteria react to fermentable carbohydrates (eg glucose)

Question 11

What does a steep gradient of recovery to regular pH on a stephan curve mean for a patient?

Answer 11

the protection mechanisms (i.e. saliva) have diminished & px is at a higher risk of developing dental caries

Question 12

what factors contribute to a drop in pH after glucose challenge?

Answer 12

1) Type and amount of CHO available
2) Bacteria present
3) Salivary composition and flow
4) Other food ingested
5) Thickness and age of dental plaque

Question 13

Why might RESTING plaque pH be different?

Answer 13

bacteria have sugar stores that are used later = there is a constant low pH and bacteria is constantly producing acid

Question 14

name 3 cariogenic bacteria

Answer 14

1) Streptococci (S. mutans)
- gram positive, sucrose, fissures,

2) Actinomyces
- gingival plaque, gingivitis

3) Lactobacilli spp,
- produce lactic acid, and lactic acid+acetate, may result in caries, require sucrose

Question 15

What is the non-specific plaque hypothesis and specific plaque hypothesis?

Answer 15

Nonspecific = plaque is pathogenic and must be removed

Specific = plaque consists of both harmful (cariogenic) and beneficial bacteria

Question 16

What is the ecological plaque hypothesis?

Answer 16

Change in local environment (e.g. frequent uptake of sugars) = shift in the balance of plaque microflora= Repeated low pH leads to growth of cariogenic bacteria (MS & Lactobacilli) = dental caries

Question 17

What is acidogenicity?

Answer 17

The ability to produce acid rapidly from fermentable carbohydrate

Question 18

What is aciduricity?

Answer 18

The ability to survive and continue to produce acid at acidic pH

• most cariogenic bacteria

Question 19

How is pH maintained in aciduric bacteria?

Answer 19

1. Low proton permeability of the cell membrane: cell wall thickening
2. Production of bases
3. Buffering capacity of the cytoplasm
4. Active transport of proton out of cell

Question 20

Where are the two sites in which bacteria stores polysaccharides?

Answer 20

1) Intracellular

2) Extracellular

Question 21

What is the intracellular storage form of carbohydrate?

Answer 21

glycogen-amylopectin

Question 22

How does IPS contribute to acidogenicity?

Answer 22

Caries-prone plaque has prolong production of acid (e.g., after meal) from IPS storage

Question 23

How does IPS contribute to aciduricity?

Answer 23

IPS –> Energy for ATPase –> Drive protons out of cell –> Adapt to low pH environment

Question 24

What is the extracellular storage form of carbohydrate?

Answer 24

Sucrose –> Glucans and fructans

Question 25

Where is the glucans and fructans transported to?

Answer 25

Diffuse into surrounding plaque

Question 26

What is the function of glucans?

Answer 26

1) Major component of interbacterial matrix

2) Barrier to the outward diffusion of acids from plaque

Question 27

Describe the storage ability of Glucans and fructans as storage carbohydrates?

Answer 27

Fructans - degrade rapidly within a few hours

Glucans - longer period

Question 28

What are the three components of the alkalinization phase which causes fluctuations in plaque pH?

Answer 28

1) Acid diffusion
2) Buffering capacity
3) Alkali from bacterial metabolism