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The major threat to teeth is?
dissolution
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The major threat of teeth is typically done by ?
acid challenges
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To counter threat DISSOLUTION by ACID CHALLENGES, what 2 things ?
1. Teeth are made at VERY LOW SOLUBILITY mineral called HYDROXAPATITE SALTS aka "spongy soluble."
2. Surrounding fluids are going to PROTECT from mineral loss.
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Product= Ksp, which is defined as the...
IP @ equilbria
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The lower the Ksp...
the LESS SOLUBLE/ MORE STABLE the salt
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CaF2 is what compared to AgCl?
less soluble
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Tooth mineral hydroxyapatites are much more complex for 2 reasons:
- 1. Variability in combinations of Ca/PO4/OH
- 2. Other ions "impurities" can be present
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Pure hydroxyapatite at Ksp?
Ksp 10^-59
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Ksp of pure complex salt hydroapatite when you subsititue F-
Ksp 10^-61
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Formation of TOOTH MINERAL done in presence of other ions that become____.
incorporate air impurities
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Most common impurity is?
carbomate Co3 2-
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Carbomate does what ?
- -destabilizes HA crystals
- -this means it increases solubility, and increases KSP
- -INCREASING KSP= BAD!!
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Biological apatite:
Contains "contaminating ions" that can have a major effect on crystal stability , thus solubility,
+ or -, see table
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Most common subsitutions are?
carbomate and fluoride
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Most common substations, carbomate & fluoride, result in enamels apatite being primarily a ?
carbonated flurohydroxyapatite with an estimated Ksp of 10^-58
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Fluoride does what to teeth?
it STABILIZES IT by DECREASING Ksp
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In tooth apatite, which is more prevalent carbomate or fluoride?
carbomate
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Ksp apatie =
- 10^-58 TOOTH KSP,
- -1/10 as stable as pure hyrdoxapatite
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When do we use IP?
when we ar NOT at equilibrium
**we only use Ksp when we are AT equilibrium
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Why is precise Ksp impossible to determine?
bcuz of its variable composition
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The principle behind protection of teeth by ions is in the ?
surrounding fluids
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AgCl example: adding Common Ion Cl-
shifts the equilibrium back to the solid according to LE CHATLIERS PRINCIPLE OF MASS ACTION
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If IP>Ksp what happens to the solid?
remineralization of the solid occurs
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In the Common Ion Effect:
-The solution is said to be?
super saturated, which is Cl here
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The common ion effect in the mouth is a ?
anti-cariogenic effect of salivary salts
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Fluids bathing the teeth contain
Calcium ions, Phosophate ions, Hydroxylate ions, and others
-not derived from the tooth mineral but other exogenous sources
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Ca, P, ion concentrations significantly affect the IP of the fluid, & thus the what of the tooth mineral?
demineralization/remineralization
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The supersaturation of fluids with HA salts does what?
MAXIMIZES tooth remineralization & LIMITS tooth demineralization
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Generalized demineralization of the teeth is known as?
EROSION
-caused by general acid in saliva
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Localized demineralization is from?
plaque bacteria produced acid , IT INIATIATES CARIOUS PROCESS
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Saliva promotes?
Remineralization
**This is a MAJOR PROTECTION MECHANISM, the Common Ion Effect
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2 ions that are PH dependent?
PO3 4- and OH-
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PO4 3- decreases with?
decreasing PH
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AS H+ increases in PH, OH- ?
decreases in PH
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The most common apatite impurity does what with decreasing pH?
carbomate, it also decreases
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AS pH drops, what does Ip do?
IP decreases
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The PH at which IP=Ksp is called?
Critical pH and is 5.5
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At ph's below the critical ph, the oral fluids are ?
UNDERSATURATED &
-the HA ionization equilibrium shifts to the RIGHT resulting in demineralization of the tooth
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Keq is?
relationship between Ksp to Ip
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If IP is high, we have LOTS OF COMMON IONS which promote?
remineralization of the tooth
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