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.
When will ionic materials precipitate into solution
will only precipitate if the surrounding solution is above the saturation point.
when will ionic materials dissolve
if the surrounding solution is below the saturation point.
when is saturation achieved
when the solubility product reaches a certain value
what is the solubility product for a binary salt XY
Ksp = [X] x [Y]
what is the solubility product for hydroxyapatite
Ksp = [Ca]10 x [PO4]6 x [OH]2
what do carbonate and magnesium ions do to the solubility product
increase the solubility product
what does fluoride do to the solubility product
decreases the solubility product making it more difficult to dissolve fluoridated crystals making it easier
what is the KSP of crystals with fluoride
With Fluoride = [Ca]10 [PO4]6 [OH]n-1[F]n+1
how do phosphate salts form
when +vely charged ions attach to the negatively charged oxygen atoms of the phosphate ions
what type of salt is hydroxyapatite crystals
calcium phosphate salt = Ca10 (PO4)6(OH)2 the positive ion is Ca2+
when will a tooth dissolve
if the pH is reduced to less than the critical pH
how many forms does the inorganic phosphate salt present in saliva or fluid
The forms depend on what
H3PO4, H2PO4–, HPO42– and PO43–, and the proportions depend entirely on the pH
at what ph does (PO4)3- change to (HPO4)2-
a pH of 9
at what ph does (HPO4)2- become H2PO4-
ph of 5
where are h+ ions produced from
from cariogenic bacteria which ferment sugars and produce lactic acid
what is the critical pH
What happens at this point
5.5 and this is when the enamel starts to dissolve
what happens at the critical pH
At around pH 5.5 and below, the phosphate in solution is in the acid form and has two protons (dihydrogen phosphateion H2PO4-
what extraneous ions can be found within the crystal structure
carbonate
magnesium
sodium and fluoride
what happens to enamel if the ph is greater than 4.5-5.5 and F is present
the biofilm fluid is supersaturated with respect to fluorapatite (FA) and there is re-precipitation of minerals in the enamel as FA.
what does the solubility of HA depend on
the pH
also the ionic levels of the HA component( calcium and phosphate of the surrounding medium