Enamel Flashcards
What are the physical properties of Enamel ?
- high modulus elasticity and low tonsils strength = hard
- the Enamel on the tooth surface would be harder , denser less porous than the subsurface
- cannot be repaired
- resist shearing force ( high resistance for abrasion )
Describe the difference between Enamel in deciduous teeth and permanent one
deciduous teeth : No difference in thickness
Permanent : it would be the thickest on the cusp tip (Incisal edge) and it decrease as we approach the cervical margin
Newly erupted Enamel appears white then over time it appear yellowish explain
due to translucency
You can see the dentine which is yellowish in color as the Enamel (white) slightly disappear
Chemical composition of Enamel
96% inorganic ,2% water, 2% organic
Calcium hydroxyapatite
its the most important component in the inorganic compounds of Enamel
Contain calcium , phosphate , and hydroxyl groups
In cross section they give hexagonal shape
Where do you find high concentration of magnesium and carbonate in the crystals ?
Explain why
in the core
Because of mineral substitution
,magnesium substitute calcium
And carbonate substitute phosphate ,
How do the crystal looks like
In the middle we have hydroxyl group
3 calcium surrounding it and 3 phosphate
And it enclose the phosphate ions with 6 calcium ions
substitution in the Hydroxyapatite
phosphate (PO4 )
calcium(ca)
Hydroxyl(oH)
in place of phosphate : Hydrogen phosphate & carbonate
in place of calcium : Mg,lead,Na,k
Hydroxy: Group 17(F,CI, I, Br)
Why do we find fluorine in toothpaste?
Inhibit caries , make the crystal hard
Carbonate effect ?
promote various attach by making the Enamel more soluble
Found in soft drink
Where can you find water?
Between the crystals surrounding the organic components
Trapped within crystalline –> hydration layer
Organic matrix varies between 1% - 2% depending on ?
the regularity of the crystals (more regular= less organic materials)
where you can find the highest concentration of proteins?
in tufts at the C EJ
What is the basic structural unit of enamel?
enamel prism (rod)
Hunter-shreger bands ?
a layer of prisms follow the same direction the blocks above and below them follow different ones
You can see them with light
pattern of prisms
Keyhole pattern
gnarled enamel
prisms over the cusps appear twisted due to crowding of ameloblast
what makes the incremental lines?
periods of Activity and inactivity of enamel
kinds of incremental lines?
Daily (cross striation)
weekly (enamel striae)
