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Flashcards in Biomineralization Deck (94)
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1

What percent of enamel is mineral?

99%

2

What percent of dentine is enamel?

70%

3

What is the purpose of organic components in mineralized tissues?

To provide scaffold and regulate process

4

What are the three organic components in mineralized tissues?

Collagen
Non-collagenous proteins
Proteoglycans

5

What is the mineral phase in mineralized tissues?

Calcium hydroxyapatite

6

What is enamel lacking that most other mineralized tissues have?

Collagen

7

In hydroxyapatite, apatite is based on what, rather than composition?

Structure, not composition

8

Is hydroxyapatite (HAP) a pure chemical compound?

Nope

9

What is a unit cell?

A conceptual entity representing the smallest section of a crystal

10

How many possible unit cells are there?

14

11

What is the lattice in crystals?

The pattern of repetition of the unit cells in a crystal

12

To which system of crystal structure do apatites belong?

hexagonal

13

What shape do naturally occurring hydroxyapaties form?

Hexagonal prisms and plate-like crystals

14

What is the shape of the hydroxyapatite lattice?

Triangular groups of 3 Ca located along c axis with each triangle rotated 60 degrees relative to the next layer

15

Where is the OH group found in a hydroxyapatite lattice?

In the center of the triangle, slightly above/below the plane

16

Why can't two OH groups be oriented toward each other in hydroxyapatite lattices?

Space restrictions

17

What lies around each crystallite?

A hydration shell

18

What are the measurements of crystals in mesenchymal hard tissues?

150-400 angstroms long
50-100 angstroms wide
25-50 angstroms thick

19

What are the measurements of crystals in enamel?

1400 angstroms long
500-800 angstroms wide
250-300 angstroms thick

20

The small size of crystals in bond and dentin mean what?

They have enormous surface area

21

Biological apatites are ___ apatites.

Substituted

22

In hydroxyapatite crystals, Ca can be substituted for what ions?

Na
Mg
Pb
Zn
Cu

23

In hydroxyapatite crystals, PO4 can be substituted for what ions?

CO3

24

In hydroxyapatite crystals, OH can be substituted for what ions?

Fl
Cl
CO3

25

Apatites of normal bone, enamel and dentin are principally what type of apatites?

Type B carbonate apatites

26

Where do ions get absorbed or bound into the apatite crystal?

In the hydration layer

27

3-6% of phosphate groups in bones and teeth are replaced by what groups?

Carbonate groups

28

Substituting carbonate groups instead of phosphate groups in the hydroxyapatite crystals has what effects?

Increased solubility
More susceptible to acid dissolution
Favors caries

29

What part of the teeth has the least amount of carbonate, Mg and Na

Enamel

30

What effects does substituting fluoride into the crystals produce?

Larger crystals
Decreased solubility
Promotes lesion repair