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Monday 1 July 2013

Enamel-1

No.
Viva Question
Answer
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
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
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