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D1 Spring - Histopathology > Week 3 - Amelogenesis & Enamel > Flashcards

Week 3 - Amelogenesis & Enamel Flashcards

(64 cards)

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1
Q

Is enamel cellular?

A

Acellular tissue

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2
Q

Does enamel have collagen?

A

No collagen in matrix

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3
Q

What does the formation of enamel involve?

A

Both secretory and resorptive activities of ectodermally derived cells

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4
Q

What is enamel harder than?

A

5x harder than dentin

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5
Q

What is the hardest tissue in the body?

A

Enamel

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6
Q

Describe the make-up of enamel?

A

Ca hydroxyapatite crystals that are large, highly oriented, and packed into rod-like structures i.e., the “enamel rod”

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7
Q

Is enamel flexible?

A

Although 96% mineral, the basic rod structure of enamel has some degree of flexibility

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8
Q

What is the composition of enamel?

A

1% water
3% organic components
96% inorganic

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9
Q

What are the organic components that make up enamel?

A

Tyrosine-rich amelogenin protein (TRAP)
- amelogenin constitutes 90% of the protein in enamel
- enamelin (5% of the protein)
- tuftelin (found in enamel tufts at DEJ)
- sheathlin

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10
Q

What is the inorganic component of enamel?

A

Calcium hydroxyapatite

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11
Q

What properties does amelogenein exhibit?

A

Thixotropic properties i.e., the ability to flow under pressure (thixotropy)

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12
Q

What happens as the enamel crystal size increases?

A

The amelogenin flows away from between the crystals and back towards the ameloblasts where it is degraded by proteolytic enzymes

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13
Q

Unlike other hard tissue proteins in which the organic matrix
remains stable (e.g., bone, cementum, dentin), in the case of enamel the organic protein is _______ and exhibits both ___________ and __________ changes

A

Labile; quantitative; qualitative

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14
Q

What kind of protein is enamelin?

A

An acidic, phosphorylated and glycosylated protein

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15
Q

What is the largest of the enamel matrix proteins?

A

Enamelin

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16
Q

Where is enamelin ristricted to?

A

The enamel rod area

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17
Q

What do the phosphorylated nature and initial accumulation near the growing ends of crystals suggest?

A

Enamelin plays a role in crystal growth and nucleation

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18
Q

Where is tuftelin restricted to?

A

The DEJ in enamel tufts

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19
Q

What does tuftelin play a role in?

A

induction, the initiation of mineralization, and possibly
functions as a junctional protein linking enamel
and dentin

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20
Q

Where is sheathlin found?

A

Throughout the rod and and interrod enamel
- However, it is preferentially located in the rod sheaths.

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21
Q

What stage specifies the “dental nature” of the underlying mesenchyme (neural crest cells)?

A

Pre-tooth bud stage

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22
Q

What do neural crest cells (ectomesenchyme) induce?

A

Formation and proliferation of the dental lamina

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23
Q

What does the dental lamina separate into/

A

Outer and inner dental epithelium

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24
Q
A

A. Stellate reticulum
B. Stratum intermedium
C. Ameloblasts
D. Mantle dentin
E. Odontoblasts
F. Pulpal cells

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25
What does the inner enamel epithelium induce?
Differentiation of odontoblasts
26
What do odontoblasts secrete?
The mantle layer of dentin
27
What happens once the mantle layer of dentin is formed?
Ameloblast differentiation is initiated and amelogenesis begins shortly thereafter
28
The gradient of cellular differentiation, matrix secretion, and mineralization during tooth development is __________ to posterior (dentition) and _________ to apical (individual teeth).
Anterior; coronal
29
What are the stages of ameloblast function?
Morphogenic stage Differentiation stage Secretory stage Maturation stage Protective stage
30
A. Stellate reticulum B. Stratum intermedium C. Ameloblasts D. Tome's process E. Enamel
31
Solid arrow points to enamel rods (running left to right). Striae of Retzius (a.k.a. incremental lines of Retzius) run from top left towards the bottom right
32
How many individual ameloblasts contribute to one enamel rod?
Four
33
Enamel rods
34
Enamel rods
35
What are structural features of enamel?
Striae of Retzius Perikymata Hunter-Schreger Bands Gnarled Enamel Enamel Lamellae Enamel Tufts Enamel Spindle
36
What are striae of retzius?
Incremental lines produced by periodic constriction of Tomes process associated with corresponding increase in the face forming the interrod enamel.
37
What do striae of retzius represent?
4-8 days of rhythmic enamel matrix apposition
38
What do cross striations on each rod represent?
24 hours of enamel matrix production
39
What are perikymata?
External (surface) manifestations of the striae of retzius
40
Perikymata
41
What are hunter-schreger bands?
an optical phenomenon produced by changes in direction of the enamel rods. - Seen only in ground histologic sections viewed by reflected light
42
Where is gnarled enamel most commonly found?
On cusp tips
43
What is gnarled enamel?
Enamel rods appear to be twisted in a complex arrangment
44
What is gnarled enamel resistant to?
Fracture and abrasion
45
What is enamel lamellae?
Hypomineralized areas of enamel extending from the DEJ for considerable distances into the enamel
46
What can enamel lamellae be involved with?
Smooth surface caries
47
What is an enamel crack?
Crack extend from the enamel surface to variable distances into the enamel - may extend into the dentin
48
What are enamel tufts?
Hypomineralized areas of enamel at the DEJ that are rich in enamelin and tuftelin
49
What do enamel spindles represent?
extensions of odontoblastic processes and tubules across the basal lamina during initial stages of matrix formation
50
What is hypomineralization of enamel related to?
A delay in the removal of amelogenin during maturation - Birthing difficulties and nutritional deficiencies also commonly disturb development
51
What is hypoplasis of enamel generally induced by?
Infectious diseases of childhood, e.g., measles, rheumatic fever, mumps, etc which leave a defect in those parts of the teeth actively developing the time of the infection
52
What does mottled enamel occur as a result of?
A diet containing relatively high levels of fluoride
53
What does severe enamel fluorosis manifest as?
Opaque areas, light-brown mottling, and surface pitting
54
What is amelogenesis imperfecta?
Defective enamel matrix deposition which, in turn, voids the possibility of enamel mineralization
55
What is the more common type of amelogenesis imperfecta?
Autosomal dominant inherited
56
What is enamel pearls and cervical enamel projections (CEP)?
Defects that occur during apposition and maturation stages of tooth development due to displacement of ameloblasts to root surface
57
What teeth do enamel pearls and CEPs most often involve?
Pearls: maxillary molars CEPs: mandibular molars
58
What is dens-in-dente?
A deep invagination of the crown or root that is lined with enamel
59
What is the prevalence of dens-in-dente and what tooth is it most commonly in?
Prevalence rate of 0.4% to 10% of all patients. Most commonly involves the maxillary incisor
60
What is the enamel thickness range over cusps?
2-2.5mm
61
What does the neonatal line represent?
an exaggerated hypomineralized striae of Retzius that forms at birth
62
What is the perikymata?
Enamel surface manifestations of the striae of retzius AKA imbircation lines of pickerill
63
What is the enamel cuticle comprised of?
Remnants of the reduced enamel epithelium
64
What is the enamel pellicle comprised of?
Glycoprotein precipitates derived from saliva and/or gingival crevicular fluids

D1 Spring - Histopathology (14 decks)

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