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MCBM Exam 3 > Biomineralization > Flashcards

Biomineralization Flashcards

(94 cards)

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1
Q

What percent of enamel is mineral?

A

99%

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2
Q

What percent of dentine is enamel?

A

70%

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3
Q

What is the purpose of organic components in mineralized tissues?

A

To provide scaffold and regulate process

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4
Q

What are the three organic components in mineralized tissues?

A

Collagen
Non-collagenous proteins
Proteoglycans

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5
Q

What is the mineral phase in mineralized tissues?

A

Calcium hydroxyapatite

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6
Q

What is enamel lacking that most other mineralized tissues have?

A

Collagen

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7
Q

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

A

Structure, not composition

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8
Q

Is hydroxyapatite (HAP) a pure chemical compound?

A

Nope

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9
Q

What is a unit cell?

A

A conceptual entity representing the smallest section of a crystal

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10
Q

How many possible unit cells are there?

A

14

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11
Q

What is the lattice in crystals?

A

The pattern of repetition of the unit cells in a crystal

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12
Q

To which system of crystal structure do apatites belong?

A

hexagonal

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13
Q

What shape do naturally occurring hydroxyapaties form?

A

Hexagonal prisms and plate-like crystals

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14
Q

What is the shape of the hydroxyapatite lattice?

A

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

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15
Q

Where is the OH group found in a hydroxyapatite lattice?

A

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

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16
Q

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

A

Space restrictions

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17
Q

What lies around each crystallite?

A

A hydration shell

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18
Q

What are the measurements of crystals in mesenchymal hard tissues?

A

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

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19
Q

What are the measurements of crystals in enamel?

A

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

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20
Q

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

A

They have enormous surface area

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21
Q

Biological apatites are ___ apatites.

A

Substituted

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22
Q

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

A 
Na
Mg
Pb
Zn
Cu
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23
Q

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

A

CO3

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24
Q

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

A

Fl
Cl
CO3

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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
31
Substituting fluoride in the apatite crystals minimizes the incorporation of what compound?
HPO4
32
Substituting fluoride in the apatite crystals minimizes the negative effects of what?
Other ions | ex. CO3
33
How many ions come together to form a unit cell? Do they do so spontaneously?
18 | No
34
Other types of solids form from calcium and phosphate. Where are these solids usually found?
In pathological conditions Ex. Whitelock Salivary stones
35
What compound may be another intermediate which causes enamel to grow as long plates?
Octacalcium phosphate
36
What is the amount of total body calcium?
1000g
37
How many grams of calcium are found outside of bone?
12g
38
About how much of our dietary calcium is excreted?
90%
39
How much total body phosphate do we have?
700g
40
About how much phosphate is found in muscle?
50g
41
How much phosphate is found outside of bone?
100g
42
What is the main source of Ca and P for bone?
Serum
43
Where were the Ca and P ions that are incorporated in mineralized tissues found?
As free ions in body fluid
44
What is the main source of Ca and P for the remineralization of enamel?
Saliva
45
How are calcium and phosphate levels in biological fluids controlled?
Homeostatically
46
What is the function of parathyroid hormone?
Responds to low serum calcium
47
How does parathyroid hormone increase blood calcium levels?
By activating osteoclasts that direct bone resorption
48
What does calcitonin do?
Responds to high serum calcium levels
49
How does calcitonin reduce blood calcium levels?
Promotes bone formation by activating osteoblasts and inhibiting osteoclasts
50
Where does vitamin D promote calcium absorption?
In the GI tract
51
What concentration of intracellular calcium concentration trigger apoptosis?
Greater than 10^-6 M
52
What is the concentration of extracellular calcium?
About 10^-3
53
What are the salivary inhibitors of crystal growth?
Statherin aPRPs PPi
54
pH below ___ starts to dissolve enamel leading to white spots, and eventually caries.
5.2
55
Although tissue fluids and saliva are supersaturated in calcium and phosphate ions, does spontaneous precipitation of CaP products does not occur. Why not?
The energy barrier must be overcome for crystallization to occur Inhibitors of crystal formation are present that raise the energy barrier Intitial ioncluster may be unstable
56
What conditions must be met for mineralization to be initiated?
Homogenous nucleation Heterogeneous mineralization Removal, inactivation or exclusion of inhibitors
57
What is homogenous nucleation?
A local increase in the concentration of inorganic ions, allowing for ionic clusters to form
58
What is heterogeneous mineralization?
Nucleating substances lower the energy barrier and allow crystalites to form without increasing the local concentrations
59
What are the two ways that bone can form?
Endochondral ossification | Intramembranous ossification
60
Which type of bone formation does not involve chondrocytes?
Intramembranous ossification
61
Why type of bone does endochondral ossification form?
Long bone
62
What type of bone does intramembranous ossification form?
Flat bone
63
What are the two mechanisms for the initiation of mineralization?
Matrix vesicle | Mineralization of collagen fibrils
64
The matrix vesicle mechanism for initiation of mineralization is found where?
Endochondral cartilage Woven bone Mantle dentin
65
The mineralization of collagen fibrils mechanism of mineralization is found where?
Lamellar bone | Circumpulpal dentin
66
What sustains crystal growth once it is initiated?
Supersaturated solutions
67
Proteolipids from oral bacteria may make a major contribution to the formation of what?
Dental calculus
68
What is the matrix vesicle?
Small, membrane bound structure that buds off a cell within first formed organic matrix
69
What does the matrix vesicle contain?
``` Alkaline phosphatase Inorganic pyrophosphatase ATPase Phospholipid Glycolipid Polysaccharide ```
70
The matrix vesicles may act as ___ ___ for crystal growth.
Nucleation sites
71
How are calcium-inorganic phosphate-phospholipid complexes formed?
Via heterogeneous nucleation
72
When the vesicle rupture, what do they provide?
Seeds for radial crystal growth to form calcospherules
73
70-80% of mineral in bone is located where?
Within the fibrils
74
What governs the process of collagen mineralization?
Non-collagenous proteins
75
As governors of collagen mineralization, how do they mediate the process?
Some act as nucleator | Others control crystal growth
76
In collagen mineralization, where does mineral first appear?
In gap zones at the ends of collagen molecules
77
The gap zones of collagen molecules are initially filled with proteoglycan and bound calcium. How is the proteoglycan removed?
Proteolytically removed
78
How is it thought that enamel mineralizes?
By crystal growth from the already mineralized dentin
79
What are the two ways for calcium to reach a mineralization front?
Diffusion between cells | Transport through cells
80
What type of junctions exist between cells in enamel formation?
Tight junctions
81
What acts as the phosphate delivery service?
Alkaline phosphatase
82
What does alkaline phosphatase do?
Hydrolyses phosphate esters with an alkaline pH optimum
83
What is a possible function of alkaline phosphatase?
*Destroy inhibitors of HAP crystal growth Transport of Pi Locally increases Pi levels
84
The autosomal recessive disease hypophosphatasia is due to what?
Mutations in TNSALP gene
85
Humans have 4 specific ALP isozymes. Three are tissue specific. What are they?
Intestine Placenta Germ cell
86
Where is the 4th ALP isozyme found?
Ubiquitous, but especially abundant in liver, bone and kidney
87
What is TNSALP?
Tissue-nonspecificl ALP
88
Where is TNSALP found?
It is the ubiquitous ALP isozyme
89
In what demographic is hypophosphataisa most commonly seen?
Inbred mennonite families of Manitoba
90
What is the major problem in hypophosphatasia?
Mineralization is defective causing: Skeletal and/or dental issues *premature loss of deciduous teeth
91
How many forms of hypophosphatasia are there?
At least 6
92
What is the major dental disease that comes from hypophosphatasia?
Odontohypophosphatasia - lack of cementum leading to: Retarded dentinogenesis Enlarged pulp chambers Premature loss of teeth
93
What type of crystal formation is affected by hypophosphatasia?
Vesicle-associated crystal formation
94
What is the main effect of a loss of the TNSALP enzyme?
Cause increased levels of PPi that act as inhibitors of HAP crystal growth

MCBM Exam 3 (9 decks)

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