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