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Endemic Oral disease > CAP 4 + 5- Plaque pH studies > Flashcards

CAP 4 + 5- Plaque pH studies Flashcards

1
Q

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

A

lactic acid

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2
Q

what is the value of the critical pH of plaque?

A

5.5

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3
Q

what happens below the critical pH of 5.5?

A

hydroxyapatite dissolves

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4
Q

Name 4 plaque pH studies.

A
  •  Metal probes e.g. antimony, irridium 
  • Glass pH electrodes
  •  Radio telemetry
  •  Removal of plaque samples
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5
Q

List the stages of R M Stephan 1944 experiment.

A
  •  Plaque on anterior tooth
  •  Antimony electrode within plaque
  •  Recorded pH
  •  2 minute rinse: 25ml of 10% glucose 
  • Recorded pH every 10 mins
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6
Q

What are the Stephan curve characteristics?

A
  • Rapid pH drop
  • slow pH rise
  • Variable time course :15-50 minutes
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7
Q

Describe the rapid drop in pH.

A

> speed microbes metabolise CHO:

  • glucose + sucrose -rapid
  • large carbohydrates e.g. starch - slow
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8
Q

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

A

Glucose or sucrose

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9
Q

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

A

starch which salivary amylase breaks into glucose and maltose

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10
Q

what effects the lowest pH of the Stephan curve?

A
  •  Microbial composition of plaque 
  • Nature of CHO source
  •  Rate of diffusion in and out of plaque
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11
Q

what causes the rise in pH?

A
  • acid diffusing out

- salivary bufferin (bicarbonate in salvia neutralises acid)

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12
Q

where does most of the buffering occur?

A

striated ducts

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13
Q

Describe Stephan curve of caries-free subjects.

A

– started higher + finished higher

– stayed above the critical pH

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14
Q

Describe Stephan curve of caries-active subjects.

A

– started lower + finished lower

– remained below the critical pH for long periods

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15
Q

what food produce a Stephan-like response?

A

carbohydrates (CHO foods)

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16
Q

What is the acidogenic potential of food?

A

the ability of food to produce acid

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17
Q

what does the acidogenic potential of food depend on?

A
  • nature of food
  • properties of the host
  • bacteria in dental plaque
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18
Q

What can be used as alternative sweeteners?

A

Nutritive sweeteners :

  • sugar alcohols
  • bulk sweeteners
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19
Q

Name 3 nutritive sweeteners.

A
  • Sorbitol
  • Mannitol
  • Xylitol
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20
Q

What is the result of using alternative sweeteners?

A
  • slowly fermented by bacteria

- only slight pH drop

21
Q

What are alternative sweeteners used in?

A

– chewing gum (mannitol)

– confectionary and toothpastes (xylitol)

22
Q

what is a problem with alternative sweeteners?

A

potential laxative effects

23
Q

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

A

Urea

24
Q

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

A

Intense sweeteners

25
Q

what quantities are intense sweeteners used?

A

small quantities

26
Q

Name and describe 3 intense sweeteners.

A 
>  Saccharin:
– ~300x sweeter than sucrose
 – Bitter aftertaste
>  Aspartame:
– Candarel and NutraSweet 
>  Acesulfame-K
– 300 X sucrose
– Soft drinks and sugar free chewing gum
27
Q

What are the conditions to term a food “tooth friendly”?

A

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

28
Q

Describe the variables in the nature of food.

A
  • 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
29
Q

Describe the host factors.

A
  • Food eating habits (sequence)
  • frequency of food intake
  • buffering capacity of saliva
  • calcium and phosphate concentrations in saliva
  • fluoride content of enamel
30
Q

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

A

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

31
Q

what is the best way to end a meal?

A

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

32
Q

what are the disadvantages of frequent snacking?

A

– More low pH episodes

– Less time for pH to recover

33
Q

what does salvia contain?

A

– HCO3- (buffer )

– Ca2+ and PO43-

34
Q

when does salivary flow increase?

A

– Masticatory-salivary reflexes

– Gustatory stimulants

35
Q

When does salivary flow decrease?

A

– At night

– Xerostomia - Gland damage (e.g. Radiotherapy)

36
Q

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

A

more salvia at floor if mouth

37
Q

when is the less buffering capacity?

A

less saliva

38
Q

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

A

– increased saliva flow

– plaque pH may rise, before dropping

39
Q

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

A

– increased saliva flow

– pH increase to resting (neutral pH) levels

40
Q

what is important in salvia flow and plaque pH?

A

Sequence of food consumption

41
Q

what should not be last in a meal?

A

sugar-containing foods

42
Q

what is good for dental health?

A

sugar-free chewing gum

43
Q

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

A
  • 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
44
Q

what acid sources cause acid erosion on the palatal surface?

A
  • dietary acid

- gastric acid

45
Q

what happens when plaque builds over enamel?

A

enamel carie lesion forms

46
Q

What happen when lactic acid touches enamel?

A

erosion of the outer surface of enamel

47
Q

Describe Silverstone’s artificial caries experiment.

A 
>  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
48
Q

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

A

lesion identical to an enamel caries lesion

49
Q

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

A
  • 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

Endemic Oral disease (13 decks)

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