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Histopathology > Amelogenesis > Flashcards

Amelogenesis Flashcards

1
Q

What are the characteristics of enamel?

A

acellular tissue
no collagen
hardest tissue in body

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2
Q

Enamel is ___ times harder than dentin

A

5

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3
Q

What does formation of enamel involve?

A

both secretory and resorptive activities of ectodermally derived cells

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4
Q

What are the calcium hydroxyapatite crystals that are extremely large, highly oriented, and packed into rod-like structures called?

A

enamel rods

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5
Q

What percent of the enamel rod is mineral?

A

96%

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6
Q

What is the composition of enamel?

A
  • 1% water
  • 3% organic components (tyrosine-rich amelogenin protein or TRAP)
  • 96% inorganic (calcium hydroxyapatite)
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7
Q

What unique property does amelogenin exhibit?

A

thixotrophic properties (ability to flow under pressure)

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8
Q

What happens to the amelogenin in the enamel crystals?

A

As the enamel crystal size increases, the amelogenin flows away from between the crystals and back towards the ameloblasts where it is degraded by proteolytic enzymes

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9
Q

What are the characteristics of enamelin?

A

acidic
phosphorylated
glycosolated protein

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10
Q

What is the largest enamel matrix protein?

A

enamelin

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11
Q

What is the possible role of enamelin?

A

crystal growth and nucleation

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12
Q

What is the possible role of tuftelin?

A

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

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13
Q

Where is tuftelin restricted to?

A

DEJ in enamel tufts

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14
Q

Where is sheathlin located?

A

throughout the rod and interrod enamel but it is preferentially located in the rod sheaths

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15
Q

What is the process of reciprocal induction?

A
  • Pre-tooth bud stage ectoderm specifies the “dental nature” of the underlying mesenchyme (neural crest cells)
  • Neural crest cells (ectomesenchyme) then induces formation and proliferation of the dental lamina
  • The dental lamina eventually separates into an outer and inner dental epithelium
  • The inner enamel epithelium induces differentiation of odontoblasts
  • Odontoblasts secrete the mantle layer of dentin
  • Once the mantle layer of dentin is formed ameloblast differentiation is initiated and amelogenesis begins shortly thereafter
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16
Q

The gradient of cellular differentiation, matrix secretion, and mineralizationduring tooth development is…

A

anterior to posterior (dentition) and coronal to apical (individual teeth)

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17
Q

What are the stages of ameloblast function?

A

 Morphogenic Stage
 Differentiation Stage
 Secretory Stage
 Maturation Stage
 Protective Stage

18
Q

What are the striae of retzius?

A

Incremental lines produced by periodic constriction of Tomes process associated with corresponding increase in the face forming the interrod enamel

19
Q

How many individual ameloblasts contribute to the composition of one enamel rod?

A

four

20
Q

Each striae of retzius represents about _______ days of rhythmic enamel matrix apposition

A

4-8 days

21
Q

What are perikymata?

A

External (surface) manifestations of the Striae of Retzius

22
Q

What are hunter-schreger bands?

A

an optical phenomenon produced by changes in direction of the enamel rods. Seen only in ground histologic sections viewed by reflected light

23
Q

What is gnarled enamel?

A

most commonly found in cusp tips. Enamel rods appear to be twisted in a complex arrangement. Very resistant to fracture and abrasion

24
Q

What are enamel lammellae?

A

Hypomineralized areas of enamel extending from the DEJ for considerable distances into the enamel. May be involved with smooth surface caries.

25
Q

What is an enamel crack?

A

Cracks extend from the enamel surface to variable distances into the enamel. May extend into the dentin.

26
Q

What are enamel tufts?

A

Hypomineralized areas of enamel at
the DEJ that are rich in enamelin and tuftelin.

27
Q

What are enamel spindles?

A

Represent extensions of odontoblastic processes and tubules across the basal lamina during initial stages of matrix formation

28
Q

What is hypomineralization of enamel primarily related to?

A

delay in the removal of amelogenin during materation

29
Q

What is hypoplasia of enamel usually induced by?

A

infectious diseases of childhood

30
Q

What causes mottled enamel?

A

diet containing high levels of fluoride

31
Q

What is amelogenesis imperfecta?

A

Defective enamel matrix deposition which, in turn, voids the possibility of enamel mineralization

32
Q

What are enamel pearls and cervical enamel projections?

A

Defects that occur during apposition and maturation stages of tooth development due to displacement of ameloblasts to root surface

33
Q

Where are enamel pearls most often?

A

maxillary molars

34
Q

Where are cervical enamel projections most often?

A

mandibular molars

35
Q

What is dens-in-dente?

A

A deep invagination of the crown or root that is lined with enamel

36
Q

What is the prevelence of dens-in-dente?

A

0.4-10% of all patients

37
Q

Where is dens-in-dente most common?

A

maxillary incisors

38
Q

Enamel thickness ranges from _____ mm over the cusps

A

2 – 2.5 mm

39
Q

The _______________ _________ represents an exaggerated hypomineralized striae of Retzius that forms at birth

A

neonatal line

40
Q

The perikymata (enamel surface manifestations of the striae of Retzius) are also known as the…

A

imbrication lines of Pickerill

41
Q

What is the enamel cuticle (nasmyth’s membrane) composed of?

A

comprised of the remnants of the reduced enamel epithelium

42
Q

What is the enamel pellicle composed of?

A

comprised of glycoprotein precipitates derived from saliva and/or gingival crevicular fluids

Histopathology (13 decks)

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