CAP 4 + 5- Plaque pH studies

Question 1

what is the product of bacteria breaking down glucose to release energy?

Answer 1

lactic acid

Question 2

what is the value of the critical pH of plaque?

Answer 2

5.5

Question 3

what happens below the critical pH of 5.5?

Answer 3

hydroxyapatite dissolves

Question 4

Name 4 plaque pH studies.

Answer 4

•  Metal probes e.g. antimony, irridium 
• Glass pH electrodes
•  Radio telemetry
•  Removal of plaque samples

Question 5

List the stages of R M Stephan 1944 experiment.

Answer 5

•  Plaque on anterior tooth
•  Antimony electrode within plaque
•  Recorded pH
•  2 minute rinse: 25ml of 10% glucose 
• Recorded pH every 10 mins

Question 6

What are the Stephan curve characteristics?

Answer 6

• Rapid pH drop
• slow pH rise
• Variable time course :15-50 minutes

Question 7

Describe the rapid drop in pH.

Answer 7

> speed microbes metabolise CHO:

• glucose + sucrose -rapid
• large carbohydrates e.g. starch - slow

Question 8

Name substrates that cause rapid diffusion and lots of acid (lactic) to cause a low pH.

Answer 8

Glucose or sucrose

Question 9

Name substrates that cause less acid (mixed) to cause a not so low pH.

Answer 9

starch which salivary amylase breaks into glucose and maltose

Question 10

what effects the lowest pH of the Stephan curve?

Answer 10

•  Microbial composition of plaque 
• Nature of CHO source
•  Rate of diffusion in and out of plaque

Question 11

what causes the rise in pH?

Answer 11

• acid diffusing out

- salivary bufferin (bicarbonate in salvia neutralises acid)

Question 12

where does most of the buffering occur?

Answer 12

striated ducts

Question 13

Describe Stephan curve of caries-free subjects.

Answer 13

– started higher + finished higher

– stayed above the critical pH

Question 14

Describe Stephan curve of caries-active subjects.

Answer 14

– started lower + finished lower

– remained below the critical pH for long periods

Question 15

what food produce a Stephan-like response?

Answer 15

carbohydrates (CHO foods)

Question 16

What is the acidogenic potential of food?

Answer 16

the ability of food to produce acid

Question 17

what does the acidogenic potential of food depend on?

Answer 17

• nature of food
• properties of the host
• bacteria in dental plaque

Question 18

What can be used as alternative sweeteners?

Answer 18

Nutritive sweeteners :

• sugar alcohols
• bulk sweeteners

Question 19

Name 3 nutritive sweeteners.

Answer 19

• Sorbitol
• Mannitol
• Xylitol

Question 20

What is the result of using alternative sweeteners?

Answer 20

• slowly fermented by bacteria

- only slight pH drop

Question 21

What are alternative sweeteners used in?

Answer 21

– chewing gum (mannitol)

– confectionary and toothpastes (xylitol)

Question 22

what is a problem with alternative sweeteners?

Answer 22

potential laxative effects

Question 23

what is used to bring pH back up after testing different sweeteners?

Answer 23

Urea

Question 24

what are the other alternative sweeteners used that are non-nutritive?

Answer 24

Intense sweeteners

Question 25

what quantities are intense sweeteners used?

Answer 25

small quantities

Question 26

Name and describe 3 intense sweeteners.

Answer 26

``` > Saccharin: – ~300x sweeter than sucrose – Bitter aftertaste > Aspartame: – Candarel and NutraSweet > Acesulfame-K – 300 X sucrose – Soft drinks and sugar free chewing gum ```

Question 27

What are the conditions to term a food "tooth friendly"?

Answer 27

If plaque pH does not fall below pH 5.7 within 30 mins of ingestion

Question 28

Describe the variables in the nature of food.

Answer 28

- Amount and type of fermentable CHO in food - Physical form ( sticky and retained vs liquid and swallowed) - Buffering capacity of food - Sialogues (saliva-flow promoters) in food - Sequence of foods in a meal

Question 29

Describe the host factors.

Answer 29

- Food eating habits (sequence) - frequency of food intake - buffering capacity of saliva - calcium and phosphate concentrations in saliva - fluoride content of enamel

Question 30

What is the differences between snacking diet and have 3 main meals.

Answer 30

In the snacking diet the pH drops below critical pH more often than the 3 times its drops at meal times

Question 31

what is the best way to end a meal?

Answer 31

end a meal with a non-acidogenic food e.g. cheese

Question 32

what are the disadvantages of frequent snacking?

Answer 32

– More low pH episodes | – Less time for pH to recover

Question 33

what does salvia contain?

Answer 33

– HCO3- (buffer ) | – Ca2+ and PO43-

Question 34

when does salivary flow increase?

Answer 34

– Masticatory-salivary reflexes | – Gustatory stimulants

Question 35

When does salivary flow decrease?

Answer 35

– At night | – Xerostomia - Gland damage (e.g. Radiotherapy)

Question 36

Where is there more salvia between the mandible and the maxilla?

Answer 36

more salvia at floor if mouth

Question 37

when is the less buffering capacity?

Answer 37

less saliva

Question 38

Describe the salvia flow and plaque pH when eating a sweet.

Answer 38

– increased saliva flow | – plaque pH may rise, before dropping

Question 39

Describe the salvia flow and plaque pH when eating a non-fermentable substance.

Answer 39

– increased saliva flow | – pH increase to resting (neutral pH) levels

Question 40

what is important in salvia flow and plaque pH?

Answer 40

Sequence of food consumption

Question 41

what should not be last in a meal?

Answer 41

sugar-containing foods

Question 42

what is good for dental health?

Answer 42

sugar-free chewing gum

Question 43

what are the factors affecting acid production with bacteria in plaque?

Answer 43

- numbers of acidogenic bacteria - types of acid produced - numbers of acid-consuming bacteria - numbers of base-producing bacteria - metabolic state of bacteria when food is ingested

Question 44

what acid sources cause acid erosion on the palatal surface?

Answer 44

- dietary acid | - gastric acid

Question 45

what happens when plaque builds over enamel?

Answer 45

enamel carie lesion forms

Question 46

What happen when lactic acid touches enamel?

Answer 46

erosion of the outer surface of enamel

Question 47

Describe Silverstone's artificial caries experiment.

Answer 47

``` > Teeth exposed to acid lose enamel mineral > Clinically: erosion > Histologically: – Generalised loss of enamel – No zone structure – No surface layer > Silverstone (1968): – Teeth were placed in lactic acid containing diffusion- limiting gels – Enamel caries-like lesions ```

Question 48

what forms when lactic acid is added to enamel when there is an diffusion limiting gel is in place?

Answer 48

lesion identical to an enamel caries lesion

Question 49

what is the summary of Silverstone's artificial caries experiment?

Answer 49

- Polysaccharides and other gel-like components of dental plaque reduce diffusion of dissolved enamel mineral away from the tooth surface - This results in the characteristic zoning of the enamel lesion