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Dental Enamel Biology and Histology
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Dental Enamel Biology and Histology
Dental Enamel Biology and Histology
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1
Question
What is the primary function of enamel in providing tooth structure?
Page 1
Answer
Enamel provides shape and contour, and it covers the anatomical crown.
2
Question
Why is enamel considered a poor conductor in the oral environment?
Page 1
Answer
Enamel is a poor conductor of heat and electricity.
3
Question
Where is enamel thickest on the occlusal surfaces of teeth?
Page 1
Answer
Thickest at the crest of cusps: incisal edge 3 mm, premolar cusp 2.3-2.5 mm, molar cusps 2.5-3 mm.
4
Question
How does enamel thickness vary in fissures, pits, and margins?
Page 1
Answer
Thinner within the fissure, pit, over the facial and cervical margin.
5
Question
Why is enamel incapable of self-repair after damage?
Page 1
Answer
Enamel is non-vital and incapable of regeneration or repair.
6
Question
What supports enamel's brittleness to prevent fracture?
Page 1
Answer
Extremely brittle, supported by underlying resilient dentin.
7
Question
What is the mineral composition percentage of enamel?
Page 1
Answer
Composed of 96% hydroxyapatite crystals and 4% proteins and water.
8
Question
How are enamel crystals organized structurally?
Page 1
Answer
Long crystals arranged in rods separated by interrod enamel.
9
Question
What are the aprismatic layers in enamel?
Page 1
Answer
Inner and outermost layers of enamel are aprismatic.
10
Question
How does enamel mineralization progress temporally?
Page 1
Answer
Partially mineralized (30%) enamel deposited first, followed by replacement of organic material by additional mineral.
11
Question
What role do enamel proteins play in development?
Page 1
Answer
Enamel proteins play an important role in regulating mineralization.
12
Question
Why does enamel lack a predentin equivalent?
Page 1
Answer
Crystallites are formed almost immediately within enamel or proteins; no equivalent of predentin or osteoid.
13
Question
List the seven physical characteristics of enamel.
Page 1
Answer
1. Extremely hard - high mineral content. 2. Hardness makes it brittle. 3. Tooth color determined by thickness. 4. Permeable to limited extent. 5. Molecular sieve and ion exchanger. 6. Specific gravity 2.8. 7. Smooth and glossy texture.
14
Question
What is enamel's overall composition by percentage?
Page 1
Answer
96-98% inorganic including water, 2-4% organic.
15
Question
Name the two main enamel proteins and their stages.
Page 1
Answer
Amelogenin (immature fetal enamel protein), Enamelin (mature enamel protein).
16
Question
What are the three structures comprising enamel composition?
Page 1
Answer
1. Enamel rods. 2. Enamel rod sheath. 3. Interrod enamel.
17
Question
What causes incremental lines of Retzius in enamel?
Page 1
Answer
Analogous rings in tree trunks, caused by metabolic changes that occur while enamel is being deposited that result in hypomineralization.
18
Question
Describe the shape and features of an enamel rod or prism.
Page 1
Answer
Enamel rod/enamel prism has head, paddle, and tail resembling a keyhole; longitudinal section shows dark lines crossing the rod; cross striation indicates daily appositional growth.
19
Question
How are enamel rods oriented relative to the DEJ?
Page 1
Answer
Direction of enamel rods oriented at right angle to DEJ.
20
Question
How do enamel rod directions vary by tooth surface?
Page 1
Answer
Pits and fissure - tent-like; proximal - horizontal; cervical permanent apically, deciduous coronally.
21
Question
What is the incremental line of Retzius?
Page 1
Answer
Cylindrical rods composed of long crystals parallel to rod axis; embedded in interrod enamel with different crystal direction; separated by thin rod sheath with organic material.
22
Question
How do non-amelogenins and amelogenins differ in enamel regulation?
Page 1
Answer
Non-amelogenins regulate mineralization; amelogenins regulate growth in thickness and width of crystals. Mineralization nucleated by apatite crystals in dentin.
23
Question
What is the neonatal line in enamel?
Page 2
Answer
The thickest striae of Retzius, darkest and thickest, reflects physiological changes around birth time; due to birth stress; enamel at cusp wavy pattern called gnarled enamel, not hypomineralized.
24
Question
What is gnarled enamel and its location?
Page 2
Answer
Wavy enamel pattern at cusp; rods intertwining irregularly from DEJ, straightens at surface for resistance to cusps/incisal edges; laid by ameloblasts for strength.
25
Question
Describe incremental lines of Retzius.
Page 2
Answer
Series of dark lines from DEJ to tooth surface (perikymata); thickest neonatal reflects birth changes.
26
Question
What produces Hunter-Schreger bands?
Page 2
Answer
Optical phenomenon from changes in rod direction; alternating light/dark bands in longitudinal ground sections under incident light; inner 2/3 enamel, outer 1/3 parallel rods.
27
Question
Define enamel lamellae.
Page 2
Answer
Hypomineralized defect extending from surface containing trapped organic material.
28
Question
What are enamel tufts?
Page 2
Answer
Hypomineralized areas rich in enamel proteins projecting from DEJ into inner 1/3 enamel.
29
Question
Define enamel spindles.
Page 2
Answer
Tip of odontoblast process trapped in enamel.
30
Question
What is amelogenesis?
Page 3
Answer
Process of enamel formation; ameloblasts begin deposition after few micrometers of dentin at DEJ.