Biochemical events in Dental Plaque

Question 1

What are risk factors for caries

Answer 1

• Orthodontic appliances
• Xerostemia (dry mouth)
• Gum tissue recession
• Radiation therapy
• Smokeless tobacco
• Excessive alcohol consumption (xerostemia)
• Patients with poor oral hygiene = bacteria

Question 2

What is the plaque composed of

Answer 2

Bacterial and salivary protein - 50%
Carbohydrates and lipids - 20-30% - extra and intracellular polysaccharides synthesised by bacteria
Inorganic components - 25% like Ca, P etc

Question 3

What is the function of plaque fluid

Answer 3

Provides an aqueous medium for diffusion and exchange of substances between saliva and tooth surface

Question 4

What is the main acid involved in caries formation

Answer 4

Lactic acid

Question 5

What contributes to the extent of oral pH drop after eating glucose

Answer 5

• Type and amount of CHO available
• Bacteria present
• Salivary composition and flow
• Other food ingested
• Thickness and age of dental plaque

Question 6

Write down the reaction of the conversion of glucose to lactic acid in yeast i think

Answer 6

Glucose –> Lactic acid + CO2 + Ethanol

Question 7

What is glycolysis also known as

Answer 7

Embden-Meyerhof-Parnas Pathway (EMP)

Question 8

What is the end product of glycolysis

Answer 8

Pyruvate

Question 9

What can pyruvate be converted into

Answer 9

1. Lactate (anaerobic)
2. Acetaldehyde and then Ethanol
3. Acetyl CoA and then further oxidation

Question 10

Name some cariogenic bacteria

Answer 10

• Streptococci (S. mutans)
• Actinomyces
• Lactinobacilli spp

Question 11

What kind of bacteria is S. mutans, what does it metabolise and where is it found in the mouth

Answer 11

Gram positive
Sucrose
Fissures

Question 12

Where is Actinomyces found in the mouth and what disease is it associated with

Answer 12

Found in gingival plaque

Gingivitis

Question 13

How can Lactobacilli produce caries

Answer 13

It produces lactic acid and acetate but this requires lactic acid

Question 14

What is acidogenicity

Answer 14

The ability to produce acid rapidly from fermentable carbohydrate

Question 15

What is aciduricity

Answer 15

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

Question 16

How do extracellular polysaccharides from cariogenic bacteria aid caries formation

Answer 16

Dietary sucrose to facilitate adherence to tooth surfaces and build up of large bacterial deposits

Question 17

How do intracellular polysaccharides from cariogenic bacteria aid caries formation

Answer 17

Storage components to prolong acid formation and acidic pH

Question 18

Write down the reaction for glucose to lactic acid in anaerobic conditions in humans

Answer 18

Glucose –> 2 lactic acid + 2 ATPs

Question 19

What do homofermentative bacteria produce

Answer 19

Almost entirely lactic acid

Question 20

What do heterofermentative bacteria produce

Answer 20

A mixture of metabolites - organic acids like acetic, propionic, succinct and formic acid

Ethanol

Question 21

What is the ecologic plaque hypothesis

Answer 21

1. Low level of MS or lactobacilli or other bacteria produce acid
2. Frequent consumption of fermentable carbohydrate
3. Best acid adaptated bacteria survive
4. Increase level of MS and lactobacilli

Question 22

How can bacteria maintain an optimum intracellular pH despite the acidic environment

Answer 22

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 23

What form are intracellular polysaccharides stored as

Answer 23

Glycogen-amylopectin

Question 24

When are intracellular polysaccharides used

Answer 24

Used as energy production and acid production when dietary CHO is depleted

Question 25

How can Intracellular polysaccharides contribute to aciduricity

Answer 25

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

Question 26

What is the role of glucans around the plaque

Answer 26

- Major component of inter bacterial matrix | - Barrier to the outward diffusion of acids from plaque

Question 27

Where can alkali generation come from in the mouth

Answer 27

1. Ureolysis 2. Strickland Reaction 3. Arginine deiminase system - major source of ammonia, S. gordonii, S. rates, S. sanguinis, lactobacilli and spirochetes use enzyme arginine deaminase to catabolise arginine in diet

Question 28

Describe the process of ureolysis

Answer 28

S. salivarius, A. Naeslundii, haemophili use enzyme urease to hydrolyse urea in saliva

Question 29

Describe the strickland reaction

Answer 29

Peptostreptococci oxidise proline in amino acids and reduce protons in plaque

Question 30

Describe the mechanism of the Arginine deaminase system

Answer 30

Major source of ammonia, S. gordonii, S. rates, S. sanguinis, lactobacilli and spirochetes use enzyme arginine deaminase to catabolise arginine in diet

Question 31

What treatment options are there for cariogenic bacteria

Answer 31

- Specific Bacterial - Bacteriocides - Pathway inhibiting chemicals - Acid neutralising smart materials - Inhibiters of IPS formation pathways

Question 32

What is dental plaque

Answer 32

An aggregation of bacteria and products onto the tooth surface

Question 33

What is the pellicle

Answer 33

Salivary components adsorbed onto the HAP surface, forms rapidly and salivary glycoproteins tend to adhere to the surface well.

Question 34

What about plaque fluid can cause cariogenic conditions

Answer 34

Changes in the ionic composition of plaque fluid can cause cariogenic conditions

Question 35

What is rested and starved plaque fluid

Answer 35

Rested - one to several hours after eating | Starved - Following overnight fasting

Question 36

What is the rough organic conc. and pH of Rested plaque fluid

Answer 36

High organic acid conc | Low pH

Question 37

What is the rough organic conc. and pH of Starvedplaque fluid

Answer 37

Low organic acid conc | Higher pH

Question 38

How long does it take bacteria to metabolise sucrose

Answer 38

about 5 mins its very quick then lactic acid will die off but won't disappear as IPS/EPS can still be used

Question 39

How does salivary pH of patients with high caries activity differ to those with low caries activity after a glucose challenge

Answer 39

- pH starts lower - pH drops to lower pH - pH recovery to resting is much slower Due to presence of different bacteria

Question 40

What contributes to the different starting pHs of patients with different levels of caries activity

Answer 40

- Bacterial composition affects metabolic properties of plaque, storage form of CHO = energy source when dieting so lactic acid is present in higher cones at rest

Question 41

Even though sucrose consumption in the population hasn't dropped hugely, why has the caries prevalence decreased largely

Answer 41

- Due to more use of fluoride - More knowledge of affects of sugar Just shows that caries aren't entirely linked to sugar consumption

Question 42

What sugars are the ones that are the most caries promoting

Answer 42

Small sugars - glucose, fructose, galactose etc

Question 43

Are sugar alcohols cariogenic

Answer 43

NOPE

Question 44

How do bacteria convert Glucose --> lactic acid

Answer 44

Anaerobic respiration

Question 45

What can pyruvate be converted into depending on the type of bacteria

Answer 45

Ethanol Totally to CO2 and H2O Lactate

Question 46

What is the key thing to remember about glycolysis and why

Answer 46

That enzymes catalyse each step, so inhibitors for certain enzymes can be used to prevent lactate production

Question 47

AY BAWS CAN I HAE DE NOTE PLZZ

Answer 47

The fate of bacterial pyruvate depends entirely on the type of bacteria present