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May14 Oral Histology > EX1; Enamel Tissue > Flashcards

EX1; Enamel Tissue Flashcards

1
Q

True or False

Enamel is the second hardest of the 4 mineralized tissues in the body

A

False; it IS THE hardest of the tissues

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2
Q

What is different about the ectodermal derived tissue that forms enamel

A

it is epithelium;

the other tissues of the tooth are connective tissue

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3
Q

What is different about the mineralization stages of enamel

A

it does not have an unmineralized or pre enamel formation stage
it has an immature (partially mineralized) and mature (fully mineralized)

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4
Q

Enamel is considered what because the ameloblast completes its enamel formative cycle once the correct thickness is achieved

A

finite

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5
Q

True or False

Enamel is the second mineralized tissue to appear

A

True; dentin is the first

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6
Q

Enamel is subject to what due to genetic and external factors (age changes, habits, smoking, etc.)

A

malformations

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7
Q

Enamel does not contain what compared to other tissues

A

enclosed cells; acellular, aneural, avascular, and alymphatic

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8
Q

*What is the definition of enamel

A

a composite biological mineral with apatite crystals oriented in a complex three dimensional pattern

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9
Q

What is apatite on the Mohs mineral hardness scale

A

5

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10
Q

What does enamel need to maintain its integrity

A

a wet environment

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11
Q

What forces is enamel subject to

A

attrition (normal)
abrasion
erosion

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12
Q

These are pathways for the diffusion of small molecules such as water and bactera

A

micropores (microporosity)

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13
Q

What is the inorganic, organic, and water weight of enamel

A

96% inorganic
1% organic
3% water

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14
Q

What is the principal mineral component of enamel

A

calcium hydroxyapatite (fluro exchanged when there is fluoride present)

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15
Q

What is the main protein (90%) composing the organic component of enamel

A

amelogenin

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16
Q

Enamel is the only tooth tissue that does not contain what

A

collagen fibers

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17
Q

How is the water distributed throughout enamel

A

via micropores between the crystals and proteins

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18
Q

What are the CEJ relationships

A

cementum overlaping enamel (most commong)
cementum meeting enamel
cementum does not touch enamel (least common)

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19
Q

What are the different configurations of the DEJ

A

scalloped

smooth

20
Q

This DEJ configuration is better adapted for occlusal forces

A

scalloped; in the coronal area

21
Q

This DEJ configuration is better for non-load bearing areas

A

smooth; in the cervical areas

22
Q

These are growth lines found on enamel

A

lines of Retzius

23
Q

These are ridges (wave-like) on the exposed surfaces of enamel centered between the lines of Retzius (grooves)

A

perikymata

24
Q

This is the structural unit of enamel

A

enamel rods

25
Q

Where are the HA crystals most dense in the enamel rod

A

in the center or core of the rod running parallel

26
Q

What forms the enamel rods

A

ameloblast (one ameloblast = one rod)

27
Q

This is the outer surface of the rod

A

enamel sheath

28
Q

How are the HA crystals of the enamel sheath arranged

A

they are less dense (more organic %) and run in different directions

29
Q

What substance is in the highest percentage of the organic material of the enamel sheath

A

amelin

30
Q

This is located between the sheath of rods

A

interrod substance

31
Q

How are the HA crystals arranged in the interred substance

A

crystals are more dense and run at different directions than the sheath

32
Q

What create the interred substance

A

two or more ameloblasts

33
Q

What causes the different optical properties of the structural components of enamel

A

density of crystals and the direction in relation to each other

34
Q

What are the direction of the rods compared to the dentin

A

they are at a 90º angle

35
Q

Ea\ch enamel rod is built up of segments separated by dark lines that give it a striated appearance, hence this name

A

interrod striations

36
Q

These extend from varying depths of the SURFACE of ENAMEL and consist of longitudinally orientated defects filled with enamel protein or organic debris (ribbon like)

A

enamel lamella

37
Q

What is the clinical significance of enamel lamella

A

access by acidophilic microorganisms (caries) and to stain substances

38
Q

These project from the DEJ for a short distance into enamel and contain a greater concentration of enamel protein (tuftelin)

A

enamel tufts

39
Q

What is the clinical significance of enamel tufts

A

contributes to the spread of caries at the DEJ

40
Q

These extend from the DENTIN across the DEJ into the enamel for a short distance

A

enamel spindle

41
Q

What is the clinical significance of enamel spindles

A

contributes to the spread of caries at the DEJ

42
Q

What makes up the enamel spindles

A

odontoblast processes extending between ameloblast and when enamel begins to form, it become embedded in the enamel

43
Q

What are the three hypomineralized enamel structures

A

enamel lamella
enamel tuft
enamel spindle

44
Q

These are alternating dark and light bands of varying width which originate at the DEJ and pass outward ending some distance from the outer enamel surface

A

Hunter-Schreager bands

45
Q

What causes Hunter-Shreager bands

A

different directions of enamel rods in adjacent layers

46
Q

What is induced by the change of enamel rod direction

A

functional adaptation;

minimizing the risk of cleavage in the axial direction under mastication

47
Q

Where does differentiation of the inner epithelial cells of the enamel organ into ameloblasts and of the peripheral cells into odontoblasts begin

A

on the coronal most site of the DEJ

May14 Oral Histology (25 decks)

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