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Histopathology > Exam 1 - Amelogenesis & Enamel > Flashcards

Exam 1 - Amelogenesis & Enamel Flashcards

1
Q

The formation of enamel involves secretory and resorptive activities of _____ derived cells.

A

ectodermally

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2
Q

Where is the enamel crystal located?

A

located in the core of the enamel rod

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3
Q

Are hydroxyapatite crystals large or small?

A

extremely large

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4
Q

Where does acid or acid-etch preferentially attack?

A

ends of the enamel crystals

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5
Q

T/F: Enamel rod structure exhibits flexibility.

A

TRUE

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6
Q

What are the percentage compositions of enamel?

A

1% water
3% organic components (TRAP proteins)
96% inorganic (HA crystals)

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7
Q

What are the 4 tyrosine-rich amelogenin (TRAP) proteins?

A

amelogenin
enamelin
tuftelin
sheathlin

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8
Q

Which organic component of enamel constitutes the bulk of the protein in enamel?

A

amelogenin

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9
Q

_____ functions in the growth of the enamel rods.

A

Enamelin

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10
Q

_____ is a linking protein found in enamel tufts along the DEJ.

A

Tuftelin

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11
Q

Where would you find tuftelin in enamel?

A

right along the DEJ

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12
Q

____ is an enamel protein found in rod sheaths.

A

Sheathlin

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13
Q

Amelogenin exhibits _____ properties, which means it is very viscous and tends to flow very slowly under pressure.

A

thixotropic

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14
Q

What property of amelogenin assists with orientation?

A

its thixotropic, flowing properties of its matrix

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15
Q

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

A

increases

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16
Q

What happens to amelogenin as enamel crystal size increases?

A

amelogenin flows away from the crystals

flows back towards ameloblasts to be degraded

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17
Q

Which proteolytic enzymes degrade amelogenin?

A

enamelysin
MMP-20
serine proteases

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18
Q

Is enamel matrix labile or stable?

A

labile (quantitative and qualitative changes)

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19
Q

____ is an acidic, phosphorylated and glycosylated protein.

A

Enamelin

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20
Q

Which organic enamel protein is the largest?

A

enamelin

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21
Q

Enamelin is ONLY found in the ____ area.

A

enamel rod

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22
Q

Enamelin is found near the growing ends of crystals and this suggests that it is involved in ____.

A

growth

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23
Q

____ is found only at the DEJ and is thought to play a role in linking and junction of enamel and dentin.

A

Tuftelin

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24
Q

The inner enamel epithelium stimulates odontoblast differentiation within the _____.

A

dental papilla

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25
Q

The _______ specifies the “dental nature” of the underlying mesenchyme (neural crest cells).

A

pre-tooth bud stage ectoderm

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26
Q

What induces the formation and proliferation of the dental lamina?

A

neural crest cells (ectomesenchyme)

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27
Q

What does the dental lamina eventually separate into?

A

inner and outer enamel epithelium

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28
Q

____ secrete the mantle layer of dentin.

A

Odontoblasts

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29
Q

Once the _____ is formed, ameloblast differentiation is initiated and amelogenesis begins.

A

mantle layer of dentin

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30
Q

What is the pattern of cellular differentiation, matrix secretion, and mineralization during tooth development?

A

anterior&raquo_space; posterior

crown&raquo_space; down (apex)

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31
Q

What are the stages of ameloblast function?

A

1) Morphogenic Stage
2) Differentiation Stage
3) Secretory Stage
4) Maturation Stage
5) Protective Stage

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32
Q

At what stage do ameloblasts start to go from low cuboidal to low columnar?

A

morphogenic stage

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33
Q

During which stage of ameloblast formation does the nucleus polarize to one side of the columnar cell, contain lots of mitochondria and form junctional complexes at the basement membrane?

A

differentiation stage

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34
Q

During which stage of ameloblast formation are odontoblasts induced by ameloblast formation at the basement membrane?

A

differentiation stage

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35
Q

Which stage induces odontoblasts to make mantle dentin?

A

differentiation stage

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36
Q

During which stage of ameloblast formation are tome’s processes formed?

A

secretory stage

37
Q

Do tome’s processes contain alkaline phosphatase?

A

YES - secrete from their granules

38
Q

What make up the forming face of enamel formation?

A

tome’s processes

39
Q

During which stage of ameloblast formation does the cell decrease in height and oscillates between a ruffled and smooth border?

A

maturation stage

40
Q

What is the purpose of the ruffled border?

A

increases surface area for adding minerals to harden enamel

41
Q

During which stage of ameloblast formation does the basal lamina attach to the ameloblasts to enamel and reduce the enamel epithelium?

A

protective stage

42
Q

During which stage of ameloblast formation does Nasmyth’s membrane form?

A

protective stage (cuticle layer)

43
Q

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

A

4

44
Q

What is the pattern of hydroxyapatite in the formation of enamel rods?

A

key hole pattern

45
Q

How wide is a typical enamel rod?

A

60 nm wide

46
Q

T/F: Enamel rods typically run superiorly to inferiorly.

A

FALSE; they run left to right

47
Q

What determines the angle enamel rods are formed at?

A

tome’s processes

48
Q

How often do tome’s processes constrict?

A

every 4-8 days

49
Q

The constriction of tome’s processes form ____, angled striations.

A

Striae of Retzius

50
Q

Striae of Retzius run ____ to the enamel rods.

A

angled/perpendicular

51
Q

Striae of Retzius are incremental lines produced by period constriction of _____.

A

tome’s processes

52
Q

What is associated with corresponding increased in the face forming interrod enamel?

A

Striae of Retzius

53
Q

What represents about 4-8 days of rhythmic enamel matrix apposition?

A

Striae of Retzius

54
Q

What are the cross striations on each rod?

A

they represent 24 hours of enamel matrix production (AKA incremental growth)

55
Q

The _____ is an exaggerated hypomineralized Striae of Retzius that forms at birth.

A

neonatal line

56
Q

What are the external surface manifestations of Striae of Retzius called?

A

perikymata (imbrication lines of Pickerell)

57
Q

Is the neonatal line hyper- or hypomineralized?

A

hypomineralized

58
Q

_____ are an optical phenomenon produced by changes in the direction of enamel rods (seen only with reflected light).

A

Hunter-Schreger bands

59
Q

Where do we most commonly find gnarled enamel?

A

in the cusp tips

60
Q

Why is gnarled enamel beneficial in cusp tips?

A

because it is very resistant to fracture and abrasion

61
Q

T/F: Gain of organization of enamel is important for occlusion at cusp tips.

A

FALSE; loss of organization allows strong gnarled enamel to form at the cusp tips and resist abrasion

62
Q

Are enamel lamellae hypomineralized or hypermineralized areas of enamel that extend from the DEJ up into the enamel?

A

hypomineralized

63
Q

What hypomineralized area of enamel may be involved in smooth surface caries?

A

enamel lamellae

64
Q

_____ extend from the DEJ up into the enamel; _____ extend from the enamel surface down to the DEJ and dentin.

A

Enamel lamellae; enamel cracks

65
Q

Enamel cracks (do/don’t) distinguish the DEJ.

A

DON’T (will keep cracking through dentin)

66
Q

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

A

Enamel tufts

67
Q

What structure at the DEJ can prevent shearing forces and breakage?

A

enamel tufts

68
Q

What are the trapped extensions of odontoblastic processes and tubules across the basal lamina during the initial stages of matrix formation called?

A

enamel spindles

69
Q

___ are processes of odontoblasts that have become trapped within the enamel matrix and then mineralized in place.

A

Enamel spindles

70
Q

_____ is delay in the removal of amelogenin during maturation of the enamel matrix.

A

Hypomineralization

71
Q

What happens if not enough amelogenin is resorbed by proteases?

A

HIGH protein content
LOW hydroxyapatite content
LOW mineralization
= enamel chips off easily

72
Q

_____ is characterized by chalky white, opaque discoloration.

A

Hypomineralization

73
Q

_____ results in notched central incisors and “mulberry molars.”

A

Hypoplasia

74
Q

What is hypoplasia usually induced by?

A

infectious childhood diseases which leave defects in teeth as they were actively mineralizing

  • measles, rheumatic fever, mumps, syphilis
75
Q

Your young patient presents with Hutchinson’s teeth and mulberry molars. What do you suspect happened during development?

A

neonatal syphilis infection OR some childhood disease that affected development

76
Q

Mottled enamel = _____; may manifest as brown spots, opaque areas and surface pitting.

A

fluorosis

77
Q

Amelogenesis imperfecta is an _____ genetic disease.

A

autosomal dominant

78
Q

What condition results from defective enamel matrix deposition that voids the possibility of any enamel mineralization?

A

amelogenesis imperfecta

79
Q

Can veneers or composite work for patients with amelogenesis imperfecta?

A

NO because composite and veneers require bonding to NORMAL tooth structure

80
Q

At what point in the stages of tooth development do enamel pearls and cervical enamel projections (CEP) occur?

A

apposition and maturation stages

81
Q

Why do enamel pearls and cervical enamel projections (CEP) occur?

A

displacement of ameloblasts to the root surface

82
Q

Enamel pearls usually involve _____; CEPs usually involve _____.

A

maxillary molars; mandibular molars

83
Q

Why are CEP detrimental to the root surface?

A

because the PDL cannot attach to enamel, so these patients are left with slippery, deep pockets

84
Q

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

A

Dens-in-dente

85
Q

Where are dens-in-dente most commonly found in patients?

A

maxillary incisors

86
Q

What is the primary problem of dens-in-dente?

A

they are followed by gross decay due to trapping of particles deep in the tooth structure

87
Q

How thick is enamel over the cusps?

A

2-2.5 mm

88
Q

The ____ is comprised of glycoprotein precipitates derived from saliva and gingival crevicular fluid.

A

enamel pellicle

89
Q

When the tooth erupts, the enamel cuticle forms and the rest of the epithelium becomes the ____.

A

junctional epithelium

Histopathology (7 decks)

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