Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
25 Cards in this Set
- Front
- Back
|
What do enamel and dentin form through? what process forms these?
|
These structures form extracellularly through highly concerted processed controlled by matrix proteins, proteases, and mineral ions that regulate nucleation, grwoth, and organization of mineral crystals.
|
|
|
What is caries initiated by?
|
initiates by dissolution of tooth mineral by organic acids made by fermentation of dietary carbs by plaque bacteria
|
|
|
What's the onset of caries dependent on?
|
on chemical propr of tooth mineral and chemistry which is generated w/in dental plaque
|
|
|
What makes up a very small percentage of enamel?
|
proteins and lipids, perhaps left over from amelogenesis
|
|
|
What 2 elements primarliy make up enamel?
|
Ca (37.5%) and P 17.7%. CO3 is the 3rd largest weight percent. Dentin, Bone, and Hydroxyapatite all have similar but not identical weight percentages
|
|
|
What component is relatively long compared to its thickness? How does this compare to this component in bone?
|
enamel crystals are very long. In bone, its more plate-like.
|
|
|
What's the stoichiometric formula for hydroxyapatite?
|
Ca5OH(PO4)3
|
|
|
What is the morphology of hydroxyapatite? What's is the definition of unit cell?
|
Long, very thin w/ hexagonal shape. Unit cell = a 3D arrangment of atoms which is periodically repeated throughout the crystal
a and b axis are of same length but c axis is slightly shorter. |
|
|
How are the Ca atoms positioned in the unit cell? how about Phosphate groups?
|
Ca ions surround each each of the hydroxyl ions. Phosphate groups associated w/ Ca ions. Relatively open structure with fair amount of space that can accomodate by various ions (ex. Fluoride, carbonate, )
|
|
|
Whats the unit cell composition of hydroxyapatite?
|
Ca10 (OH)2(PO4)6
|
|
|
When you add fluoride to hydroxyapatite, what component will it subsititue for?
|
hydroxyl group. Hydroxyl ion is smaller, and does not sit in the same plane as Ca atoms. The F does sit int eh same plane as ca toms so there's much mroe association.
|
|
|
Define solubility
|
amt of dissolved substance per unit volume required to reach saturation (equilibrium)
|
|
|
What is fluoride's effect on solubility of Ca?
|
It reduces the solubility of enamel when fluoride is incorporated into the tissue.
|
|
|
What happens to the solubility of hydroxyapatite at ph below 5 in acetic acid and lactic acid?
|
greatly increases. For ph 4, solubility goes to 13 and 14 in acetic acid and lactic acid respectively.
|
|
|
What does the degree of saturation need to be in order to be considered saturated? DS = ?
|
1. Less than 1 is undersaturated and greater than 1 is supersaturated.
|
|
|
What happens when you place enamel in an undersaturated soln? Supersaturated?
|
undersaturated - dissolves
supersaturated - precipitates. |
|
|
What's the first mineral formed in bone?
|
Dicalcium phosphate dihydrate. Goes through 3 more phases in order to become hydroxyapatite.
|
|
|
With respect to tooth enamel, what is saliva - supersaturated, undersaturated or saturated?
|
Supersaturated medium. Proteins in saliva prohibit saliva from precipitating even though its supersaturated.
|
|
|
What happens to DS if Ca increases? If ph Decreases?
|
DS increases if Ca increases. If Ph decreases, then DS also decreases.
|
|
|
What are some explanations for presence of intact surface layer in incipient carious lesion?
|
1) intrinsic properties of enamel surface (higher F, zinc, mineral content, lower carbonate)
2) gradients in solubility or porosity 3) adsorption of inhibitors onto the enamel surface (proteins, F-) 4) reprecip of less soluble mineral phases at the enamel surface |
|
|
What 2 things happen in the demineralization of enamel?
|
dissolution, and reprecipitation of ions at the surface. These two properties refer to the KINETICS of enamel demineralization.
|
|
|
As you increase DS, what happens to the rate of dissolution? What is this dependent on?
|
Rate of dissolution decreases. depends on amt of Ca in the solution
|
|
|
What happens to the demineralization onset as DS increases?
|
the onset of demineralization also increases. therefore, affects the rate!
|
|
|
How can you reduce the rate of deminieralization?
|
lower acidity or enhance DS. or you can place a barrier on the surface.
|
|
|
Is the concept of critical pH valid? I.e. when Ph is below 5, everything dissolves?
|
NO! Actually, different composition of solutions will effect the degree of dissolution, even if all are at the same pH. Can have different DS values.
|
