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DEN 7111 Development > Exam 3 - Amelogenesis Davenport > Flashcards

Exam 3 - Amelogenesis Davenport Flashcards

1
Q

Hallmark of bell stage

A
  • form of the tooth is determined
  • hard tissues start being produced
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2
Q

When does the primary epithelial band form?

A

37 days

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3
Q

What is the primary epithelial band

A

continuous band of thickened epithelium forms around the mouth in the presumptive upper/lower jaws

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4
Q

____ corresponds to the future dental arches

A

Primary epithelial band

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5
Q

Two subdivisions of the primary epithelial band

A
  • vestibular lamina
  • dental lamina
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6
Q

Dental lamina gives rise to

A

Teeth

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7
Q

Teeth will be ____ to the vestibular lamina

A

Lingual

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8
Q

Stages of tooth development

A
  • bud
  • cap
  • bell
  • early crown
  • crown
  • late crown formation
  • root formation and eruption
  • function
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9
Q

In what stage of tooth development does dentinogenesis occur?

A

Early crown stage

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9
Q

In what stage of tooth development does amelogenesis occur?

A

Crown stage (after dentinogenesis)

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10
Q

_____ is marked by histodifferentiation and morphodiferentiation

A

Bell stage

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11
Q

Enamel organ consists of:

A
  • inner enamel epithelium
  • outer enamel epithelium
  • stellate reticulum
  • stratum intermedium
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12
Q

Enamel is secreted as ____ and does not contain ____

A

Partially mineralized substance; fibers

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13
Q

Cells of the inner enamel epithelium are ____ in nature. The nuclei are ___ located

A

Cuboidal; centrally to basally (sitting on basement membrane where future DEJ is)

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14
Q

To begin dentinogenesis, the cells of the ______ begin to line up along the basement membrane, and these cells will begin to ____. Then they eventually produce ____

A

Dental papilla; elongate; predentin

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15
Q

What is the signal for amelogenesis to begin?

A

When predentin mineralizes and forms dentin

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16
Q

How does amelogenesis begin? (describe changes in cells involved)

A
  • cells of inner enamel epithelium undergo transformation of polarity; become columnar
  • nucleus goes to proximal side of cell, cell machinery between nucleus and basement membrane
  • distal face becomes secretory
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17
Q

What is the process that extends from the secretory face of the odontoblast to the DEJ?

A

Tome’s fiber

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18
Q

Initial layer of enamel after dentin mineralizes

A

Aprismatic enamel

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19
Q

Aprismatic enamel does not contain:

A

Enamel rods

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20
Q

Ameloblast projection on distal face is called:

A

Tome’s process

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21
Q

Tome’s process secretes:

A

Enamel rods

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22
Q

Unit structure of enamel is called

A

Enamel rod

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23
Q

What is perpendicular to the DEJ?

A

Haversian systems

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24
Q

As you go up the contour of the tooth, what changes?

A

Angle of the rods are different

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25
Q

Enamel maturation occurs after:

A

The full width of enamel has been deposited

Influx of mineral makes crystals larger, increases thickness and width

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26
Q

When is enamel maturation fully completed?

A

When tooth is erupted and comes into contact with oral fluids (saliva)

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27
Q

3 stages of amelogenesis

A
  1. presecretory
  2. secretory
  3. maturation
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28
Q

Stage prior to production of enamel

A

Presecretory stage

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29
Q

Aprismatic enamel and Tome’s process is formed during the:

A

Secretory stage

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30
Q

What covers the crown of the tooth until it is ready to erupt?

A

Reduced enamel epithelium

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31
Q

When does Tome’s process retract?

A

Maturation phase

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32
Q

What happens during presecretory stage of amelogenesis?

A
  • phenotype differentiation
  • polarity change
  • develop secretory machinery (ER, golgi, mitochondria)
  • prepare to secrete enamel
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33
Q

Ameloblasts carry out multiple activities during their:

A

Life cycle

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34
Q

Ameloblasts may _____ depending on developmental requirements

A

Upregulate or downregulate

35
Q

Differentiation of IEE and OEE begins at what parts of the tooth?

A

Cusps or incisal edge (enamel knot is unique structure to this area)

36
Q

Amelogenesis progresses in what direction?

A

Cervically

37
Q

Blood supply changes during what stage?

A

Amelogenesis

38
Q

True or false: the initial layer of enamel contains enamel rods

A

False - aprismatic enamel

39
Q

What part of the enamel organ needs to be present in order to form enamel?

A

Stratum intermedium

40
Q

After enamel rod formation, there is a ____ transition and formation of ____ layer. Then, the ____ forms to protect the crown of the tooth

A

Postsecretory; papillary; Reduced enamel epithelium

41
Q

The ___ is a potential space

A

DEJ

42
Q

Is the DEJ a smooth interface?

A

No, it is intercalated to tighten the fit of the enamel over the dentin

43
Q

In general, is there any mixing of the enamel and dentin?

A

No, as long as dentin is produced before enamel. Enamel spindles can form however

44
Q

During mantle dentin formation, what happens to the basement membrane?

A

Perforates and degenerates

presecretory stage in amelogenesis

45
Q

During the early secretory stage of amelogenesis, the cells have a ____ face. During the active secretory stage, _____ develops

A

smooth face (aprismatic enamel); Tomes’ process

46
Q

Secretion is ____ during the secretory phase of amelogenesis

A

Constitutive

continuous; no storage of secretory granules

47
Q

The secretory phase of amelogenesis is described as having:

A

Intense synthetic and secretory activity

48
Q

Is there a lag phase in initiation of mineralization during amelogenesis?

A

No

49
Q

True or false: enamel crystals interdigitate with those with dentin

A

True
surface of dentin is scalloped and enamel fits in the edges

50
Q

Interrod substance is also known as

A

Junctional complexes

51
Q

Face of Tome’s process secretes:

A

Enamel rod

52
Q

What is the “rule of 4”?

A

Takes 4 ameloblasts to produce one rod, and 1 ameloblast contributes to 4 rods

53
Q

Dentin is produced at a rate of:

A

4 microns a day

54
Q

Enamel rod is _____ to the DEJ

A

Perpendicular

however forms more of sinusoidal curve

55
Q

Maximum thickness of enamel

A

2.5mm

56
Q

Are enamel rods in phase with one another? Why is this significant to enamel structure?

A

No; contributes to strength of the enamel as long as there is support from the dentin underneath

57
Q

What happens during the maturation phase of amelogenesis?

A
  • Transitional phase: morphology changes, reduced by half
  • Maturation Proper: modulation produces smooth end/ruffle-ended ameloblasts to transport calcium, secretion of covering basal lamina (enamel cuticle); collapse of enamel organ leads to reduced enamel epithelium
58
Q

What is the modulation cycle in ameloblasts?

A

Goes between smooth end and ruffle ended

59
Q

Maturation requires a gradient in order to:

A

Deposit enamel that goes from the DEJ to the surface of the tooth - otherwise center will be gooey

60
Q

Ameloblast secretory products

A
  • amelogenins
  • enamelin and ameloblastin
  • tuftelin
  • Proteases

non-collagenous proteins (enamel proteins and enzymes)

61
Q

____ make up 90% of ameloblast secretory proteins

A

Amelogenins

62
Q

____ make up 10% of non-amelogenin proteins

A

Enamelin and ameloblastin

63
Q

Amelogenins are controlled by:

A

Genes on both X and Y chromosome (sexual heterogeneity)

64
Q

Amelogenins undergo what kind of processing?

A
  • short and long term extracellular processing by proteolytic enzymes into tyrosine rich amelogenin polypeptide (TRAP)
  • has to be broken down in order for mineralization and maturation to occur
65
Q

True or false: amelogenins directly nucleate, shape, or orient crystal ribbons

A

False - they do not

66
Q

Amelogenins function

A
  • separates and supports ribbons
  • expands matrix to accommodate ribbon elongation
  • regulates growth in thickness/width, prevents them from fusing during formation
  • must be removed to prevent subsequent enlargement of crystals during maturation
67
Q

When does amelogenin expression stop?

A

When enamel reaches full thickness

68
Q

Amelogenins inhibit:

A

lateral growth of HA crystals

69
Q

What happens if there is a loss of function of amelogenins?

A

thin hypoplastic enamel layer is formed that lacks enamel rods

70
Q

Amelogenins are a ____ group of proteins

A

Heterogenous (5-45 kDa)

71
Q

Non-amelogenin proteins are _____ proteins

A

65 kDa sulfated proteins

72
Q

Both amelogenin and non-amelogenin proteins undergo:

A

Extracellular processing

73
Q

Function of non-amelogenin proteins

A

Promote and guide formation of enamel crystals

74
Q

Ameloblastin is mostly found in:

A

Newly formed enamel matrix

75
Q

Ameloblastin has what binding properties?

A

Calcium

76
Q

Mutant ameloblastin causes:

A
  • aborting enamel formation
  • enamel organ regresses and becomes cystic
77
Q

Largest and least abundant of enamel matrix proteins?

A

Enamelin

78
Q

Where is enamelin present?

A

Only at growing enamel surface, not detected inside forming enamel

79
Q

Enamelin is ____ to crystal growth but ____ crystal elongation

A

Inhibitory; promotes

80
Q

Loss of function of enamelin

A

no defined enamel layer

81
Q

Proteinases function

A

Have to do with Ca/phosphate binding

82
Q

Inner enamel epithelium - Functional stages

A
  1. Morphogenetic
  2. Histodifferentiation
  3. Initial secretory (no Tomes’ process)
  4. Secretory (Tomes’ process)
  5. Maturative (ruffled end)
  6. Maturative (smooth end)
  7. Protective/desmolytic
83
Q

During which stage does change in polarity of ameloblasts occur?

A

Histodifferentiation (presecretory)

84
Q

Between what 2 stages is there a modulation of activity?

A

Maturative stage - ruffled end and smooth end

85
Q

What happens during the protective/desmolytic stage?

A

After enamel completion, enamel organs collapse and form reduced enamel epithelium over the surface of the tooth

DEN 7111 Development (19 decks)

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