CSA Chemistry of mature human enamel

Question 1

whats the hierarchy structure in dental enamel?

Answer 1

o	Tooth in section
o	Enamel/ Dentine 
o	Enamel prisms 
o	Enamel crystals
o	Individual crystal

Question 2

What do rods or prisms comprise of?

Answer 2

bundles of hex. crystals

Question 3

what are the crystals?

Answer 3

Ca Hydroxyapatite

Question 4

what is difference between non and biological CaHAP?

Answer 4

many other crystals present and the apatite can vary in size and morphology.

Question 5

what are the growth of crystals regulated by?

Answer 5

AMELOGENIN (formed by ameloblasts)

Question 6

what is the crystallographic cell unit defined by?

Answer 6

positioning of OH ions

Question 7

what is the structure of Ca HAP like?

Answer 7

•hydroxyl groups at centre (black on yellow)
•surrounded by triangle of calcium ions
•Alternating with calcium ions are phosphate ions
• Surrounding these rings are hexagon of calcium ions
o These are known as calcium 1
• calcium 1 shared with another hexagonal unit cell

Question 8

How do OH ions run in CaHAP?

Answer 8

centre of elongated Hex structure

Question 9

what does electronegativity of fluoride do when in hydroxyl position of HAP?

Answer 9

pulls electrons towards it, pulls ions closer

structure more rigid &harder

Question 10

What does fluoride do to hydroxyl column?

Answer 10

• re-orientates hydroxyl H bonds towards fluoride ion - stabilises structure even more (pulls all the hydrogen towards it)

Question 11

What ions can get substituted into the lattice?

Answer 11

Mg, Bicarbonate ,

Question 12

what are the properties of Bicarb?

Answer 12

very soluble, no electronegativity so weakens the structure

Question 13

Sample of human dental enamel?

Answer 13

physical density decreases from surface to interior

Question 14

Where are the lower densities in enamel?

Answer 14

near the fissure

Question 15

What exist in the inner regions of enamel?

Answer 15

more water, space and maybe protein

Question 16

what is outer surface of molar and incisors like?

Answer 16

hard and dense

Question 17

what happens as you move inwards towards ADL

Answer 17

less DENSE

Question 18

What is HAP distribution in mature human dental enamel like?

Answer 18

Mineral content higher towards outer regions than inner regions

Question 19

where is most protein found?

Answer 19

at ADJ

Question 20

where is higher levels of Carbonate in human molar enamel?

Answer 20

outer region

Question 21

Why is enamel harder on outside?

Answer 21

less carbonate incorporated into HAP

Question 22

What happens to magnesium conc. towards dentine surf?

Answer 22

increase 3 to 4 fold

Question 23

Where are low levels of magnesium ?

Answer 23

on outside of enamel

Question 24

What are inversely proportional ?

Answer 24

Mg and Densities since impurities weaken enamel

Question 25

What does outermost enamel contain?

Answer 25

most fluoride from toothpaste

Question 26

What if teeth have more F?

Answer 26

less MG and tooth is stronger

Question 27

What are DENTINE apatite crystals like compared to enamel?

Answer 27

smaller than enamel

Question 28

What does dentine contain?

Answer 28

higher level of carbonate than Magnesium

Question 29

Where is dentine apatite embedded?

Answer 29

in organic matrix of type 1 collagen

Question 30

What is dentine collagen like?

Answer 30

highly cross linked and stable

Question 31

What does dentine collagen account for?

Answer 31

more than half of the tissue

Question 32

What are apatite crystals like?

Answer 32

more thin and ribbon like

Question 33

What is interior enamel like?

Answer 33

less dense, contains more carbonate and magnesium and less fluoride
so less stable