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CSA SR > Chemistry of enamel caries > Flashcards

Chemistry of enamel caries Flashcards

1. To understand the chemical changes occurring in dental enamel during caries, against the background of enamel chemistry. 2. To understand how the chemistry of enamel caries is related to therapeutic measures such as fluoride and calcium-based technologies.

1
Q

When will ionic materials precipitate into solution

A

will only precipitate if the surrounding solution is above the saturation point.

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2
Q

when will ionic materials dissolve

A

if the surrounding solution is below the saturation point.

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3
Q

when is saturation achieved

A

when the solubility product reaches a certain value

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4
Q

what is the solubility product for a binary salt XY

A

Ksp = [X] x [Y]

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5
Q

what is the solubility product for hydroxyapatite

A

Ksp = [Ca]10 x [PO4]6 x [OH]2

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6
Q

what do carbonate and magnesium ions do to the solubility product

A

increase the solubility product

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7
Q

what does fluoride do to the solubility product

A

decreases the solubility product making it more difficult to dissolve fluoridated crystals making it easier

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8
Q

what is the KSP of crystals with fluoride

A

With Fluoride = [Ca]10 [PO4]6 [OH]n-1[F]n+1

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9
Q

how do phosphate salts form

A

when +vely charged ions attach to the negatively charged oxygen atoms of the phosphate ions

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10
Q

what type of salt is hydroxyapatite crystals

A

calcium phosphate salt = Ca10 (PO4)6(OH)2 the positive ion is Ca2+

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11
Q

when will a tooth dissolve

A

if the pH is reduced to less than the critical pH

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12
Q

how many forms does the inorganic phosphate salt present in saliva or fluid

The forms depend on what

A

H3PO4, H2PO4–, HPO42– and PO43–, and the proportions depend entirely on the pH

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13
Q

at what ph does (PO4)3- change to (HPO4)2-

A

a pH of 9

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14
Q

at what ph does (HPO4)2- become H2PO4-

A

ph of 5

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15
Q

where are h+ ions produced from

A

from cariogenic bacteria which ferment sugars and produce lactic acid

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16
Q

what is the critical pH
What happens at this point

A

5.5 and this is when the enamel starts to dissolve

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17
Q

what happens at the critical pH

A

At around pH 5.5 and below, the phosphate in solution is in the acid form and has two protons (dihydrogen phosphateion H2PO4-

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18
Q

what extraneous ions can be found within the crystal structure

A

carbonate
magnesium
sodium and fluoride

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19
Q

what happens to enamel if the ph is greater than 4.5-5.5 and F is present

A

the biofilm fluid is supersaturated with respect to fluorapatite (FA) and there is re-precipitation of minerals in the enamel as FA.

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20
Q

what does the solubility of HA depend on

A

the pH

also the ionic levels of the HA component( calcium and phosphate of the surrounding medium

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21
Q

what are acids in the biofilm converted to in the saliva

A

converted into salts by the bicarbonate buffer system

22
Q

what happens as a result of acid being converted into salts

A

the pH increases to above 5.5
biofilm becomes super saturated in regard to hydroxyapatite or fluroapatite
calcium and phosphate lost by enamel can be more efficiently recovered if fluoride is still present in the biofilm.

23
Q

what is a white spot lesion

A

This is due to dissolution by acid produced by bacteria. The acid produces tiny pores which dry out producing a white spot due to light scatter

24
Q

describe the translucent stone

A

large and uniform pores

25
Q

what is the dark zone

A

INCREASE OF POROSITY but also small pores inaccessible to the imbibing fluid

26
Q

what is the body of the lesion

A

much more porosity with very large pores and as if some re-precipitation of dissolved mineral has occurred

27
Q

what is removed from the first layer of enamel

A

magnesium and carbonate rich

28
Q

how much calcium is lost from sound enamel

A

37%

29
Q

how much P is lost from sound enamel

A

18.5%

30
Q

how much CO3 is lost from sound enamel

A

2-4%

31
Q

how much Mg is lost from sound enamel

A

0.2-0.4%

32
Q

how much Ca is lost from translucent zone

A

around 30%

33
Q

how much P is lost from translucent zone

A

around 13%

34
Q

how much CO3 is lost from translucent zone

A

around 28%

35
Q

how much MG is lost from translucent zone

A

around 2%

36
Q

how much Ca is lost from the dark zone

A

around 35%

37
Q

how much P is lost from the dark zone

A

16.6%

38
Q

how much CO3 is lost from the dark zone

A

3%

39
Q

how much Mg is lost from the dark zone

A

3%

40
Q

how much Ca is lost from the body of the lesion

A

37%

41
Q

how much P is lost from the body of the lesion

A

18.5%

42
Q

how much CO3 is lost from the body of the lesion

A

1%

43
Q

how much Mg is lost from the body of the lesion

A

0.16%

44
Q

why might the amount of carbonate lost from sound enamel and lost from dark zone be similar

A

due to re precipitation

45
Q

what is the conclusion of % chemistry loss

A

The conclusion is that there is selective removal of easily dissolved mineral at an early stage. This agrees with the effect of both magnesium and carbonate on hydroxyapatite.

46
Q

where is fluoride conc highest in the zones of a carious lesion

A

at the carious surfaces and in the translucent zone

47
Q

which minerals are lost first

A

magnesium and carbonate

48
Q

what is biomimetic remineralisation

A

techniques which attempt to mimic nature with respect to remineralisation.

49
Q

what is an example of biomimetic remineralisation

A

Casein Phospho-peptide: Amorphous Calcium Phosphate (CPP-ACP): Tooth mousse
self assembling peptides(SAPS)

50
Q

describe CPP-ACP

A

Ca2+ and PO3−4 in solution by binding to form nanoclusters.

The desired effect is inhibiting demineralization and driving remineralisation down a concentration gradient.

51
Q

DESCRIBE sap

A

bioactive peptides synthesised from natural amino acids which have shown some promising results

52
Q

how do SAPs work

A

Mimic enamel matrix proteins which control initial mineral deposition ‘nucleation’ and subsequent crystal growth.
Increase net mineral gain via inhibition of demineralisation and promotion of remineralisation.
Are candidate materials for “Filling without Drilling”

CSA SR (52 decks)

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