Answers for Enamel -3
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Maximum thickness of enamel in deciduous dentition
in molar cusps |
1.3 mm
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Volume of water in enamel
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5 to 10%. This is crucial as a lot of ions cross
in to tooth in liquid medium |
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Water in enamel is in form of
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hydration layer coating enamel crystals and
filling enamel defects |
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Prism patterns in human enamel
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Three types are seen – Pattern 1 – circular;
pattern 2 – prism arranged in parallel rows; pattern 3 – arranged in staggered row “key hole” pattern |
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Basic unit of enamel
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Enamel prism
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Organic material are often accommodated along
enamel prism boundary because of |
Microporosity
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The predominant pattern of arrangement of enamel
rods in human is |
Type III or key hole pattern
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Key hole pattern or type III pattern is made by
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Large ameloblasts
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Small ameloblasts produce
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Pattern II or parallel arranged fashion of enamel crystallites
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Enamel between prisms are called
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Interprismatic enamel
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Why does interprismatic enamel have different
optical property |
Owing to crystal deviation by 40 to 60 degrees in
orientation. Abnormal abrupt change of orientation responsible for refraction of light |
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The angle at which interprismatic crystallites
cross prisms is |
60 degrees
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Stacks of ______enamel prisms follows are
unidirectional after which they follow different direction |
10 to 13 layers
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Transversely sectioned zones in Hunter-Schereger
bands are |
Diazones
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Longitudinally sectioned zones in Hunter-Schereger
bands are |
Parazones
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The average width of Hunter-Schereger bands are
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50 micrometers
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The angle between diazones and parazones of enamel
is about |
40 degrees
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Where will be Hunter -Schreger bands be absent
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when all enamel rods runs in same direction, as in
outermost 25% of enamel, the bands will be absent |
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width of non-prismatic enamel in a newly erupted
teeth |
Deciduous 20 – 100 micrometers and permanent teeth
20 to 70 micrometers. Enamel crystallites are aligned at right angle to surface and hence parallel to each other. |
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why is the outer most layer of enamel highly
mineralized |
Remineralization by saliva; absence of prism
boundaries. |