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No.
|
Viva Question
|
Answer
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|
1
|
Enamel is thickest on the
|
Cusp tips
|
|
2
|
The maximum thickness of enamel in humans is
|
2 to 2.5 Millimeters
|
|
3
|
The hardest calcified tissue in the body is
|
Enamel
|
|
4
|
The time lapse between hard tissue matrix secretion and
mineralization is minimal in |
Enamel
|
|
5
|
The inorganic portion of enamel is
|
96%
|
|
6
|
The number of enamel rods is estimated to be about
|
5 to 12 million
|
|
7
|
The longest enamel rods are observed at the
|
Cusps
|
|
8
|
The submicroscopic appearance of enamel is described to
be |
Key hole
|
|
9
|
The enamel rods are perpendicular to a tangent in
|
Enamel surface
|
|
10
|
The diameter of the enamel rod is smallest at the
|
Dentino-enamel junction
|
|
11
|
The average diameter of an enamel rod is
|
4 micrometer
|
|
12
|
The diameter of rods increases from dentinoenamel junction
towards the surface at a ratio of about |
1 to 2
|
|
13
|
Fish scale appearance of enamel rods is appreciated in
|
Demineralized sections
|
|
14
|
Striations along the enamel rods are of a uniform length
of |
4 micrometer
|
|
15
|
In general, the enamel rods are oriented at
|
Right angle to dentin
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|
16
|
The enamel rods are approximately horizontal in
|
Cervical and central parts of a deciduous crown
|
|
17
|
In permanent teeth, along the cervical margin, enamel rods
deviate |
Apical direction
|
|
18
|
Tortuous pathways of the enamel rods near cuspal tips are
referred to as |
Gnarled enamel
|
|
19
|
Hunter- Schreger bands is a functional adaptation to
|
Minimize risk of fracture
|
|
20
|
The change in direction of enamel rods is responsible for
the optical appearance of |
Hunter-Schreger bands
|
|
21
|
Hunter-Schreger bands can be best visualized in ground
sections of |
Longitudinal section of teeth under oblique reflected
light |
|
22
|
Bands of Hunter Schreger extend through the
|
Inner two-thirds of enamel
|
|
23
|
Bands of Hunter Schreger are produced due to
|
Change in the rod direction; Altering the direction of
incident illumination; Variations in enamel content |
|
24
|
The successive apposition of layers of enamel during crown
formation is visualized as |
Incremental line of Retzius
|
|
25
|
Enamel is heavily calcified at
|
Surface
|
|
26
|
Striae of Retzius continue on the surface on enamel as
|
Perikymata
|
|
27
|
Perikymata on enamel surface are parallel to each other
and to |
Cementoenamel junction
|
|
28
|
The number of perikymata in occlusal area is
|
10 per millimeter
|
|
29
|
The number of perikymata, in areas excluding occlusal area
is |
30 per millimeter
|
|
30
|
The enamel rod ends are
|
Concave
|
|
31
|
Enamel rod ends are shallowest at
|
Cervical regions
|
|
32
|
Enamel rod ends are deepest at
|
Incisal edge / cuspal tip
|
|
33
|
Neonatal line is an accentuated incremental line of
Retzius observed in |
Deciduous teeth
|
|
34
|
Nasmyth’s membrane is formed by the
|
Reduced enamel epithelium
|
|
35
|
The thin leaf like hypocalcified structure from outer
surface of enamel to dentinoenamel junction is the |
Enamel lamellae
|
|
36
|
Enamel lamellae have
|
Major organic and little inorganic matter
|
|
37
|
Difference between enamel crack and lamellae
|
Crack disappear while lamellae persist
|
|
38
|
Enamel lamellae are thought to develop due to
|
Plane of tension
|
|
39
|
The enamel lamella that is restricted to enamel is
|
Type A
|
|
40
|
Enamel tufts arise from
|
Dentinoenamel junction
|
|
41
|
Enamel tufts reach to
|
One fifth to one third of enamel thickness
|
|
42
|
The inner end of enamel tuft lies in the
|
Dentin
|
|
43
|
The dentinoenamel junction is scalloped with the
|
Convexities facing dentin
|
|
44
|
Enamel spindles are
|
Extension of odontoblastic process in to enamel
|
|
45
|
With increasing age, enamel shows
|
Decrease incidence in caries
|
|
46
|
Enamel is laid down by
|
Ameloblasts
|
|
47
|
During morphogenesis stage of inner enamel epithelium, the
cells are |
Short and columnar
|
|
48
|
During morphogenesis stage of inner enamel epithelium, a
large nucleus is positioned at |
Central position
|
|
49
|
During morphogenesis stage of inner enamel epithelium, the
Golgi apparatus and centrioles are located in |
Proximal end
|
|
50
|
During ameloblasts differentiation, mitochondria migrate
to the |
Basal end
|
|
51
|
Reversal of polarity of the inner enamel epithelium or
future ameloblasts occurs in |
Organizing stage
|
|
52
|
With the initial dentin deposition, Inner enamel
epithelium proceeds to the |
Formative stage
|
|
53
|
In maturative stage of inner enamel epithelium, the cells
of the stratum intermedium display microvilli at |
Mesial end
|
|
54
|
The shape and structure of outer enamel epithelium is
altered with |
Dentin formation
|
|
55
|
The defined ameloblast layer is lost during the phase
of |
Protective stage
|
|
56
|
With the collapse of enamel organ the cuboidal stratum
intermedium changes its shape to |
Spindle shape
|
|
57
|
The function of reduced enamel epithelium is to
|
Protect mature enamel
|
|
58
|
Loss of reduced enamel epithelium before eruption leads
to |
Resorption of enamel; Deposition of cementum over enamel;
Anomalies of enamel |
|
59
|
The basement membrane of dental papilla is also known as
|
Dentinoenamel membrane
|
|
60
|
The proof for the fact that the distal end of enamel rods
are not in direct contact with dentin is the presence of |
Dentinoenamel membrane
|
|
61
|
The projection of ameloblasts in to the enamel matrix is
known as |
Tomes processes
|
|
62
|
An enamel rod is formed by
|
Four ameloblasts
|
|
63
|
The amount of organic portion initially secreted by
ameloblasts removed during mineralization of enamel is as much as |
90%
|
|
64
|
With the initial mineralization, the amount of enamel that
is mineralized is about |
30%
|
|
65
|
The initial enamel crystals are
|
Ribbon shaped
|
|
66
|
During mineralization of enamel matrix, the process
initiates from |
Cuspal tip
|
|
67
|
During mineralization of enamel matrix, the process
initiates from |
Dentinal end of rods
|
|
68
|
The nucleator for enamel crystallization is from
|
Apatite crystallites and tuftelin
|
|
69
|
The enamel layer that is heavily mineralized as soon as it
is formed |
Layer adjacent to dentinoenamel junction
|
|
70
|
The enamel layer adjacent to dentinoenamel junction is
heavily mineralized as soon as it is formed is due to the presence of |
Tuftelin
|
|
71
|
The dependence of enamel to be formed on the presence of
preformed dentin is an example of |
Reciprocal induction
|
|
72
|
Of the enamel proteins 90% belong to a group of
heterogeneous low molecular weight proteins called as |
Amelogenins
|
|
73
|
The gene coding for amelogenin contains at least _______
codons |
Seven
|
|
74
|
Tuftelin is limited to the
|
Amelodentinal
junction |
|
75
|
No matrix vesicle is found in association with the initial
mineralization of |
Enamel
|
|
76
|
Acellular zone of dental papilla disappears with
|
Odontoblast differentiation
|
|
77
|
The junction of the enamel and the ameloblasts has a
picket fence or saw toothed appearance due to the projection of |
Tomes process
|
|
78
|
The basal lamina supporting ameloblast disintegrates with
the |
Predentin deposition
|
|
79
|
The distinction of the Tome’s process with that of the
cell body of ameloblasts is marked by |
Distal terminal web
|
|
80
|
Formation of enamel matrix wall is by the Tome’s process
at |
Periphery of the cell; Close to Junctional complexes;
Adjacent to proximal part of the Tome’s process; Along with the secretion from adjoining ameloblasts the matrix wall is synthesized, which latter becomes the inter-rod enamel. Secretion from the side of the Tome’s process fills the pit created by the former, which latter becomes the enamel rod. |
|
81
|
Enamel rod and inter-rod enamel differ in
|
Orientation of crystallite
|
|
82
|
The enamel protein highly concentrated in rod sheaths is
the |
Amelin or sheathlin
|
|
83
|
The boundary where the crystals of the enamel rod meet
those of the inter-rod region at sharp angles is the |
Enamel rod sheath
|
Prof. Rooban Thavarajah
Oral and Maxillofacial Pathologist
List