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Monday, 1 July 2013

Dentin-1


Question
Answer
1
The bulk of the tooth is formed by the:
Dentin
2
The cell bodies of odontoblast are arranged along the:
Pulpal surface of dentin;
Explanation: Though the odontoblasts are the dentin producing cells, like other mineralized cells, they do not lie in the tissue they form but lie in dentin.
3
Physically and chemically the dentin resembles the:
Bone
4
The main morphologic difference between bone and dentin is that bone has osteocytes while dentin has:
Odontobalstic process;
Dentin contains only the processes of the cells that was responsible for its formation where as bone contains the cell body itself within the matrix itself as the osteocyte.
5
The color of dentin gradually with age becomes:
Darker.
With age dentin accumulates numerous fibers and other materials that render the dentin darker.
6
The organic content of dentin is:
35%
7
The unit cell of hydroxyl apatite has a formula of:
3 Ca 3 (PO4)2.  Ca  (OH)2
8
The calcium hydroxyapatite has a formula of
Ca 10 (PO4)6 (OH) 2
9
The hydroxyapatite crystals in dentin have a shape of:
Plate;
Fish scale appearance is in light microscopic appearance of enamel rods in cross section. Stubby rhombic crystals are the shape of biological hydroxyapatite crystals.
10
The dentinal matrix of collagen fibers is arranged in a:
Random network
11
Each odontoblast gives rise to:
One process
12
The dentinal tubule has a:
Doubly curved course
13
The dentinal tubules have a straight course at:
Root apex area; Cervical area of crown; Incisal edges/ cuspal tips
14
From the pulp, the first convexity of dentinal tubules is directed towards the:
Apex of the tooth
15
Each of the dentinal tubule is oriented to the pulpal surface at:
Right angle
16
The dentinal tubule ends at the enamel/cementum at:
Right angle
17
The ratio between outer and inner surface of dentin is about:
Five: one.
Hence nearer to the pulp, dentinal tubules are closely packed and outer most area of dentin it is spaced apart.
18
The diameter of dentinal tubules at the pulpal cavity is about:
3 to 4 micrometers
19
The diameter of dentinal tubules at the enamel/ cementum end is about:
1micrometer
20
1 mm2 of cavity prepared approximately exposes
30,000 dentinal tubules
21
The ratio of the number of tubules per unit area on the pulpal to outer surface of dentin is about:
Four: one.
Notes: Nearer to the pulp, dentinal tubules are closely packed and outer most area of dentin it is spaced apart. Moreover the surface area at the inner surface is lesser than the outer surface area of dentin.
22
At the pulpal surface, the dentinal tubules per mm2 area are:
50,000 to 90,000 tubules
23
The dentinal tubules per mm2 area are highest in:
Crown
24
The dentinal tubules are very closely packed towards:
Pulpal surface
25
The lateral branches of dentinal tubules are referred to as:
Canaliculi
26
The diameter of canaliculi of dentin at the enamel/ cementum end is about:
Less than 1micrometer
27
To the main dentinal tubules, the canaliculi originate at:
Right angle
28
The dentin that immediately surrounds the dentinal tubule is the:
Peritubular dentin
29
The highly mineralized dentin is
Periubular dentin
30
The type of dentin that has poor collagen content & is highly mineralized is
Peritubular dentin
31
The ratio of thickness of peritubular dentin between outer and inner surface of dentin is:
Two : one.
Notes: The thickness of peritubular dentin in dentinoenamel junction is 0.75 micrometers while at the outer surface it is 0.40 micrometers. This peritubular dentin causes the constriction of dentinal tubules to about a micrometer in the dentinoenamel junction.
32
The dentinal tubule wall has an organic lining called as:
Lamina limitans.
It is a thin organic membrane that has high content of glycosaminoglycans.
33
The main body of dentin is made of:
Intertubular dentin
34
Intertubular dentin is observed between:
Zones of peritubular dentin
35
After demineralization using acid, the mineralized structure that does not retain the matrix is the:
Peritubular dentin
36
The width of adult human predentin is:
a.       2 to 6 micrometers
37
The hydroxyapatite crystals are formed along the randomly distributed fibers in intertubular dentin with their long axes oriented __________ to the collagen fibers.
Parallel to the tubule
38
During decalcification the type of dentin that is lost is
Peritubular dentin
39
The newly formed dentin is referred as
Predentin
40
The unmineralized dentin is:
Predentin
41
The odontoblastic processes are largest at the:
Pulpal end
42
The length and diameter of odontoblast cell bodies are approximately:
7 and 40 micrometers.
The odontoblastic processes are about one micrometer and 200 to 300 micrometer in length.
43
The odonoblastic process is composed of:
Microtubules and small filaments
44
The first ever synthesized dentin in a tooth is referred as:
Mantle dentin.
It is the outermost peripheral part of primary dentin.
45
The width of mantle dentin is about:
20 micrometers.
The width of coronal mantle dentin may be up to 150 micrometer thick.
46
The area of initial dentin matrix formation is observed as:
Mantle dentin
47
The dentin formed prior to root completion is called as:
Primary dentin.
The dentin formed prior to root completion is primary dentin, the bulk of which is the circumpulpal dentin. The dentin formed after root completion is the secondary dentin. Tertiary dentin is formed in response to noxious stimuli.
48
The dentin formed after root completion is referred as:
Secondary dentin
49
The junction of primary and secondary dentin is marked by:
Sharp bend. Schreger line
50
The fine lines or striations in dentin are referred as:
Imbrication lines or incremental lines of von Ebner.
51
The incremental lines of von Ebner reflect the:
Daily rhythmic pattern of dentin matrix deposition. It is about 4 to 8 micrometer in crown and still less in roots. Recent studies have proved that each incremental line of von Ebner are actually 20 micrometer apart and represent a 5 day increment.
52
The lines of von Ebner run:
Right angle to dentinal tubules
53
Accentuated lines of von Ebner are referred as:
Contour lines of Owens
54
The area of hypomineralization between globules of calcification is referred to as:
Interglobular dentin
55
Interglobular dentin is found:
In circumpulpal dentin
56
In interglobular dentin the dentinal tubules pass:
Uninterruptedly through the matrix
57
The interglobular dentin is an area affected by a defect of:
Mineralization
58
In transmitted light, in root dentin, the zone adjacent to cementum is:
Tomes granular layer
59
The reason for the appearance of Tomes granular layer is:
Looping of distal portion of dentinal tubules
60
The theories that explain the pain transmission through dentin are
Direct neural transmission theory; Hydrodynamic theory; Transduction theory
61
The most popular and widely accepted theory of the pain transmission through dentin is:
Hydrodynamic theory
62
The theory in which the existence of dental lymph is suggested is:
Hydrodynamic theory
63
The theory in which the existence of neurotransmitter vesicles inside dentinal tubules was suggested is:
Transduction theory
64
Dentin is a vital tissue because it
Contains odontoblasts and its processes
65
The injured odontoblast processes synthesize:
Reparative dentin
66
Dead tracts appear black in:
Transmitted light
67
Numerous nerve endings are seen in:
Predentin. From pulp nerve endings extend up to a level of 100 – 150 micrometers.
68
Sclerotic dentin is found generally in teeth of: 
Aged
69
Sclerotic dentin is formed due to:
Occlusion of the dentinal tubules with hydroxyapatite
70
Dentin formation begins at:
The cusp tip & incisal edge region
71
The daily increments of dentin formed are approximately:
4 micrometers.
This is in the primary dentin and it is one micrometer per day in secondary dentin. Tertiary dentin formation rate depends on the stimulus and is some times more than 5 micrometers per day.
72
The common pattern of mineralization in normal dentin is:
Linear & globular
73
Dentin formation is a function of:
Dental papilla cells
74
The cells of the dental papilla are of:
Ectomesenchymal origin
75
Dentin is produced by:
Odontoblasts
76
The initial site of dentin deposition will mark the position of the:
Dentinoenamel junction
77
Dentin formation takes place:
Before enamel formation
78
With age the pulp chamber is reduced in size due to the deposition of (In absence of any pathology):
Secondary dentin
79
The enzyme that is essential for formation of the dentin is:
Alkaline phosphatase
80
Dentin formation begins at:
Late bell stage
81
In multicusped teeth, the formation of dentin begins:
Independently.
It is independently occurring at the site of future cusp tips and spreads down as each flank are fused.
82
The amount of dentin deposited as tooth reaches its functional position in the occlusion is:
Two third of root dentin.
As the tooth reaches the occlusion, only two third of the root dentin is deposited. After eruption the entire root dentin is deposited. This takes approximately 18 months in deciduous dentition and 2 to 3 years in permanent dentition after teeth erupts in to the oral cavity.
83
A progressive reduction in a normal pulp cavity size is associated with:
Secondary dentin.
Tertiary dentin is associated with pathological or aging process.
84
The acellular zone between dental papilla and inner enamel epithelium is eliminated by the:
Odontoblasts.
It is eliminated by the differentiating odontoblasts which increase in size and occupy this zone.
85
The component of the ground substance that has been found to transfer the inductive ability of the inner enamel epithelium to the superficial dental papillary cells is:
Heparan sulfate.
The growth factors such as the TGF beta-1, BMP2, IGF have been identified as the factors that are secreted by the inner enamel epithelium to induce odontoblast differentiation.
86
The organic matrix of mantle dentin contains an aperiodic collagen belonging to:
Type VII collagen
87
Matrix vesicles essential for mineralization of dentin is secreted by:
Odontoblasts
88
The phosphoprotein that is unique to circumpulpal dentin is the:
Phosphoporyn.
It is absent in Predentin and mantle dentin and is associated with mineralization.
89
Diffence between Predentin and dentin:
Less or no mineralization;
Higher amount of proteoglycans; Having higher quantities of chondroitin 6 sulfate.
90
During mantle dentin formation, the blood capillaries are found in the:
Sub-odontoblastic layer.
During circumpulpal dentinogenesis, these capillaries are bound between the odontoblastic layers and after odontogenesis they become sub-odontoblastic in position.
91
Largest of interglobular dentin are formed in the:
At areas of fast dentin deposition.
Though the largest of interglobular dentin are seen just below the mantle dentin in the circumpulpal dentin, they are seen only when the rate of dentin deposition is the fastest.
92
The difference in coronal dentin and root dentin is:
Orientation in collagen molecule;
Phosphoryn content is less in root dentin; Rate of deposition is slower in roots
93
Odontoblasts move or retract in:
Centripetally
94
The amount of mineral phase that is within the collagen is about:
56%
95
When the cells forming tertiary dentin are included in to the dentin itself, it is called:
Osteodentin
96
The first formed collagen in mantle dentinogenesis is deposited near the Hertwig’s epithelial root sheath’s basal lamina in a:
Parallel fashion.
In coronal mantle dentinogenesis, the first formed collagen fibers are deposited at right angles to the basement membrane.
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