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oral histology > Enamel Tissue: Histologic Structure and Clinical Considerations > Flashcards

Enamel Tissue: Histologic Structure and Clinical Considerations Flashcards

1
Q

what is the hardest mineralized tissue in the body

A

Enamel

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2
Q

what part of the tooth is not a connective tissue

A

Enamel

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3
Q

what is enamel derived from

A

from specialized epithelial cells from the ectoderm

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4
Q

what is the cell that makes enamel

A

Ameloblasts

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5
Q

what stage doe enamel lack that other mineralized tissues have

A

No unmineralized or preenamel formation stage

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6
Q

stages of enamel growth

A 
Immature stage (partially mineralized)
Mature stage (fully mineralized)
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7
Q

when is enamel formed

A

The second mineralized fissue in the tooth(after dentin)

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8
Q

what organic substance is not found in enamel that other mineralized tissue has

A

No collagen fibers

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9
Q

what is enamel tissue

A

a composite biological mineral with apatite crystals ariented in a complex 3d pattern

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10
Q

what is the most clinically significant part of the tooth

A

Enamel

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11
Q

what is enamel equal to hardness in

A

Mild steel

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12
Q

what is the mohs mineral hardness of apatite

A

5

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13
Q

when is Enamel brittle

A

when no dentin support

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14
Q

why is enamel translucent

A

Thinness

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15
Q

Hue of enamel depends on

A

location level
surface conditions of enamel
Attraction to stain substances
Age changes

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16
Q

what is needed for enamel to maintain its integrity

A

Wet environment

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17
Q

what is the form of tooth wear that is normal

A

Attrition

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18
Q

what causes attrition

A

Slow wearing away of tooth substance under the stress of mastication

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19
Q

what causes abrasion

A

Non-normal wear

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20
Q

what causes erosion

A

Chemicals (see acid erosion)

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21
Q

what are the pathways in the enamel for diffusion of small molecules and water

A

Micro porosity

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22
Q

what on the pore walls can lead to carious lesions

A

Electrochemical effects

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23
Q

when mineral is returned to the molecular strucutre via saliva

A

Remineralization

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24
Q

when does cavitation occure

A

when demineralization exceedes remineralization

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25
Q

what makes up enamel by wieght

A

96% Inorganic
1% organic
3% water

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26
Q

what is the inorganic substance of enamel

A

Hydroxyappatie crystals

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27
Q

what separates Hydroxyapetite in enamel vs other mineralized tissue

A 
Larger
more impurities (fluoride, carbonate)
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28
Q

what makes up 90% of the organic substance of enamel

A

Amelogenin

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29
Q

roll of Amelogenin for enamel

A

Seed protein for normal mineralization

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30
Q

how are enamel proteins arranged

A

Lace like pattern throughout the volume of enamel, closely associated with the surface of the cystals

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31
Q

how is water distributed in the enamel

A

Micropores between crystals and proteins

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32
Q

what does the water form around the crystals in enamel

A

Hydration shell

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33
Q

importance of hydration shell in enamel

A

Ruote of F ions
Ca and P ion for remineralization
Whitening
Acidophic organisms (caries)

34
Q

what happens to enamel as you age

A 
Wears slowly (attrition)
darkens
Composition changes
reduced porosity
systemic age changes
35
Q

ageing reduces porosity which means

A

Reduced susceptibility to cares

36
Q

what does the composition of enamel change as you age

A

Fluoride increases

37
Q

where is the DEJ scalloped

A

Coronally

38
Q

why is the DEJ scalloped coronally

A

Adaptation to occlusial forces

39
Q

where is the DEJ smooth

A

Cervical non-load bearing areas

40
Q

what is the most common CEJ relationship

A

Cementum overlaps enamel

41
Q

what is the second most common CEJ relationship

A

Cementum meets enamel

42
Q

what is the least commone CEJ relationship

A

Does not meet enamel

43
Q

how consistent are CEJ relationships

A

Can vary even on different sides of the tooth

44
Q

What are the GRowth lines of enamel

A

Strae of Retzius

45
Q

the numerous small transverse ridges on the exposed surface of enamel

A

Perikymata

46
Q

what forms the PErikyma

A

The striae of Retzius form enamel grooves on the surfaces and the Perikyma form as the ridges

47
Q

how long does it take for each perikyma to form

A

8-10 days

48
Q

The structural unit of enamel

A

Enamel rods

49
Q

size of enamel rods

A

diamter of 5-6 micrometers

length of 2.5 mm(wavey)

50
Q

where are Hydroxyapatite crystals are more dense in the enamel rods

A

the center or core of the rod

51
Q

what direction do enamel rodscrystals run

A

PArallel to the long axis of the rod

52
Q

How Many Ameloblasts form each anemal rod

A

1 ameloblast

53
Q

what is the outer surface of an enamel rod

A

Enamel sheath

54
Q

density of crystal in the enamel sheath

A

less dense (more organic substance)

55
Q

what direction do enamel crystals run in the enamel sheath

A

different directions

56
Q

what makes up most of the organic material of the enamel sheath

A

Amelin

57
Q

what is the stuff between sheaths of the enamel rods

A

Interrod substance

58
Q

density of the cystals of the interrod substance

A

More dense that the sheath

59
Q

what direction do the crystals of the interrod substance rub

A

In a different direction that those of the sheath

60
Q

how many ameloblasts secrete interrod substance

A

2+

61
Q

why are enamel rods wavy

A

For strength yo

62
Q

why are enamel rods segnemented

A

Sometime the ameloblasts take a rest and therefore stop creating an interrod stritations

63
Q

what direction do enamel rods lie in relation to the dentin

A

at a right angle

64
Q

where do Enamel lamella extend

A

Extend in varying depths from the surface of enamel

65
Q

what are Enamel Lamella filled with

A

Enamel protein

ORganic debris from the oral cavity

66
Q

Clinical significance of enamel lamella

A

Can cary acidophhilic microorganisms for caries

Stain substances

67
Q

where do Enamel tufts extend from

A

From the DEJ for a short distance into enamel

68
Q

what is found in an enamel tuft

A

A greater concentration of enamel protein

69
Q

Clinical significance of an enamel tuft

A

Contribute to the spread of caries at the DEJ

70
Q

where do enamel spindles extend from

A

From the dentin to cross the DEJ into the enamel for a short distance

71
Q

Clinical significance of an enamel spindle

A

Contribute to the spread of caries along the DEJ

72
Q

How do enamel spindles form

A

Odontoblast shoot processes between the ameloblasts.

When dentin and enamel formation begins the process become embedded in the new enamel

73
Q

what are Hunter-schreager brnads

A

Alternating dark and light bands of varying width, originating at the DEJ border and pass outward ending at some distance from the outer enamel surface

74
Q

What causes the Hunter-Schreager bands to form

A

Different direction of enamel rods in adjacent layers

75
Q

why do enamel rods change directions to form Hunter-Schreager bands

A

Minimize the risk of cleavage in the axial direction due to mastication

76
Q

what forms the ameloblasts

A

Inner epithelial cells of the enamel organ

77
Q

what forms the Odontoblasts

A

peripheral cells of the dnetal papilla

78
Q

where does Odontoblast and ameloblast differentiation occur first

A

At the more coronla site of the future DEJ

79
Q

what type of cell are ameloblasts

A

Columnar epithelail cells

80
Q

what are Enamel pearls

A

Ectopic enamel formation

81
Q

if tetracyclin stain is near the roots when was the antibiotic taken

A

Later in the pregnancy

82
Q

what causes mulberry molars

A

Congenital syphilis

oral histology (14 decks)

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