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Flashcards in Biomineralization Deck (68):
1

What is the mineral that makes up most of mineralized tissues of body

hydroxy apetitie

2

What are the mineralized tissues

1. enamel (99% mineral)
2. dentin (70% mineral)
3. cementum (40%)
4. bone (70%)

3

What are the mineralized tissue components

1. organic components (proteins and soft molecules)
2. Mineral phase

4

What are the organic components

provide scaffold and regulate process
1. collagen (except enamel)
2. non collagenous proteins
3. proteoglycans

5

what is part of the mineral phase

calcium hydroxyapetite (HAP) crystallites

6

what are features of HAP

1. Not a pure compound
2. apatite is based on structure, not composition

7

How many diff crystal sytems are there

7:
1. cubic
2. tetragonal
3. orthorhombic
4. hexagonal
5. monoclinic
6. triclinic
7. trigonal

8

What is a unit cell?How many ind units are there

a conceptual entity rep. the smallest section of a crystal that reps the structure of the solid as a whole. There are 4 types of units

9

what is a crystal made up of

multiple repeats of a unit cell.

10

What are the 4 types of unit cell

1. I: body centered
2. F: face centered
3. C: side centered
4. P: primitive

11

what is a crystal lattice

crystals are made of identical unit cells stacked in some ordered fashion. The infinite array of identical points is the crystal lattice.
-The pattern of repetition of the unit cell.

12

A HAP crystal forms ____shaped prisms and plate like crystals

hexagonal

13

space restrictions prevent two ___groups oriented to each other so they dont interfere with each ohter

OH

14

Mesenchymal hard tissues are much ____than enamel

smaller; it has greater SA and more oppertunities for other molecules to interact with crystals of bone and dentin bc of this.

15

What is around crystals?

hydration layer; a layer of water exists around each crystallite that contains molecules that substitute into crystal and restructure it

16

Biological apatites are ____apatites

substituted

17

What can calcium be substittued for

1. Na
2. Mg
3. Pb, Zn, Cu

18

What can PO4 be substituted for

carbonate

19

What can OH be substituted for

F, Cl, CO3

20

Apatites of normal bone, enamel, and dentin are principally:

type B carbonate apatites
-B type: carbonate for phosphate
-A type: carbonate for hydroxyl

21

Carbonate makes the crystals ____ and flouride make the crystals

weaker; stronger

22

Explain effect of carbonate substituion on the mineral phase

1. Changes dimension of crystal
2. increases its solubility
3. more susceptible to acid dissolution
4. favors caries.

23

___contains the least amount of carbonate, Mg, and Na. ___ and dentin contain the most

Enamel; bone

24

What is the effect of flouride substitution on the mineral phase

-Substitutes for OH in unit cell:
1. makes crystals larger; more tightly packed
2. Dec's solubility
3. Promotes repair of caries lesions by remineralization
4. Promotes formation of F-HAP
5. Minimizes incorporation of HPO4
6. minimized negative effects of other ions

25

How is HAP formed in the body

By intermediate steps
1. Calcium and phosphorus form brushite
2. Brushite forms whitlockite

26

which intermediate is the most stable form

HAP

27

How many grams of calcium in body

1000g; 12 g outside of bone; 1-1.5 in body fluids

28

What is needed for absorption of calcium

Vitamin D

29

What is the amount of phosphate in body

700g; 100g outside of bone; 50 g in muscle

30

What are sources of Calcium and phosphate for mineralizaiton

Free ions in body fluids. Serum is the main source of Ca and P for bone. Ca in body has to be tightly reg. Important for brain and muscle function.

31

There is a ____fold diff between Ca inside of cell than Ca outside of cell

1000

32

_____ is the main source of Ca and P for remineralization of enamel

Saliva

33

Calcium and phosphate levels in biological fluids are _____controlled

homeostatically

34

How does parathyroid hormone function

Stimulates cells on surface of bone and Acts to release Calcium to keep levels high. It activates osteoclasts and directly resorb bone and put it back into serum and also work on kidney to reabsorb calcium.

35

How does calcitonin function

Promotes bone formation. Activates osteoblasts to put calcium back onto the bone.

36

What do Vitamin D metabolites do

Absorption of calcium from the GI tract.

37

If intracellular calcium concentration is higher than 10^-6 :

you get apoptosis

38

What is the amount of calcium extracellularly

10^-3

39

____ and ___ are supersaturated with respect to HAP

Serum and saliva; If there were no inhibitors, the crystals would continue to grow, but there ARE inhibitors in saliva.

40

What are the salivary inhibitors

1. Statherin
2. aPRPs (acidic proline rich proteins)
3. PPi (pyrophosphates)
-In order to remineralize teeth you have to get rid of these.

41

When is saliva supersaturated

7.4

42

At what pH will enamel dissolve

below 5.2; white spots lead to caries

43

What is the mechanism of crystallization

formation of a cluster of ions requires energy; so an energy barrier must be overcome for crystallization to occur; Inhibitors of crystal formation are present that raise the energy barrier.

44

What is regulated in order for mineralization to occur

1. the initiation and amount of mineralization
2. the crystal size
3. the shape

45

What conditions must be met in order for mineralization to be initiated

1. Homogenous nucleation: a local increase in the conc of inorganic ions allows a suff. number of ionic clusters to form.
2. Heterogenous mineralization:nucleating sub's lower the energy barrier and allow crystallites to form w/o inc. the local conc.'s.
3. Removal, inactivation or exclusion of inhibitors.

46

What are two ways bones are formed

1. Endochondral ossification
2. Intramembranous ossification

47

What is endochondral ossification

1. Start off with cartilage; chondryctes --> osteoblasts; guide the mineralization of the cartilage: allow formation of long bones

48

What is intramembranous ossification

NO cartilage involved. Ostebolasts produce osteoid which is type 1 collagen: form flat bones; ex: scapula, sternum, ribs, patella

49

What are two mechanisms of initiation

1. matrix vesicle
2. mineralization of collagen fibrils

50

What is the mechanism of matrix vesicle predominant in

1. endochondral cartilage
2. woven bone
3. mantle dentin

51

what is the mechanism of mineralization of collagen fibrils predominant in

1. lamellar bone
2. circumpulpal dentin

52

What is involved in both mechanisms of crystal growth

phopholipids; find CaPi phopsholipid complexes in calcified tissue and proteolipids from oral bacteria make contribution to formation of dental calculus.

53

Explain how matrix vesicles function in mineralization

ACt as nucleation sites for crystal growth; calcium inorganic phosphate phospholipid complexes form inside, you then get heterogenous nucleation. Vesicles then rupture and provide seeds for radial crytal growth to form calcospherules.

54

The inorganic part of bone matrix is

HAP

55

What are the organic components of bone matrix

88% type 1 collagen and the rest are regulators; they either inhibit or promote bone formation

56

What is the process of colalgen mineralization

Mineral forms within the collagen; HAP molecules become seated once the inhibitors are removed from the spaces. Molecules form firbrils and become mineralized bet the end. Fibrils make fibers which make patterns called osteons.

57

In bone, ____% of mineral is loc within the fibrils

70-80%

58

T/F Collagen itself likely has no role in initiation

True

59

Process of collagen mineralization is governed by ___ ____ proteins

non collagenous proteins; they're also thought to influence the size and shape of crystals that form

60

Compare and contrast how dentin is mineralized vs bone

Dentin: Odontoblasts have long projections; when teeth are being formed, these form collagen fibrils on which mineralization occurs. Odontoblasts sends projection from inside to outside of tooth which creates canals, this allows inside of tooth to be sensitive in changes of pressure, etc.
Bone: osteoclast removes surface; it gets refilled in; osteblast lays down matrix and fills in holes. Collagen molecules mineralize and form bone.

61

State the principle diff's bet enamel and other mineralized tissues

Enamel doesnt involve collagen at all! Enamel grows by already mineralized dentin. Size and shape of crystals det by enamel matrix proteins (amelogenin, enamelin, etc).

62

List known matrix proteins implicated in the control of matrix mineralization, and their postulated functions.

osteopontin, ostenectin, BSP II, dentin sialoprotein,

63

How does calcium get to mineralization front?

1. transport through cells
2. diffusion between cells

64

How does phosphate get to mineralization front

Alkaline phosphatase

65

Describe the general properties of ALP, and list potential functions in mineralization

1. Locally inc Pi levels
2. Destroys inhibitors of HAP crystal growth
3. Transport of Pi
4. Ca++ binding protein
5. Ca/Mg ATPase
6. Tyrosine specific phosphoprotein phosphatase

66

Explain the molecular basis of hypophosphatasia

Tissue non specific ALP isozyme is in liver, bone and kidney. An autosomal recessive disease, hypophosphatasia can happen due to mutations in TNSALP gene:
-Serum calcium and Pi levels are normal
-Mineralization defective: skeleton/dentition can be affected. Premature loss of deciduous teeth, a major clinical feature.
-In fetus can cause death

67

What is odontohypophosphatasia

-Dental disease
-incisors most affected
-premature loss of teeth due to lack of cementum
-enamel is ok

68

What does hypophosphatasia affect

vesicle associated crystal formation
-main effect of loss of enzyme may be due to cause of increased levels of PPi.