EX1; Enamel Tissue Flashcards Preview

May14 Oral Histology > EX1; Enamel Tissue > Flashcards

Flashcards in EX1; Enamel Tissue Deck (47):
1

True or False
Enamel is the second hardest of the 4 mineralized tissues in the body

False; it IS THE hardest of the tissues

2

What is different about the ectodermal derived tissue that forms enamel

it is epithelium;
the other tissues of the tooth are connective tissue

3

What is different about the mineralization stages of enamel

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

4

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

finite

5

True or False
Enamel is the second mineralized tissue to appear

True; dentin is the first

6

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

malformations

7

Enamel does not contain what compared to other tissues

enclosed cells; acellular, aneural, avascular, and alymphatic

8

*What is the definition of enamel

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

9

What is apatite on the Mohs mineral hardness scale

5

10

What does enamel need to maintain its integrity

a wet environment

11

What forces is enamel subject to

attrition (normal)
abrasion
erosion

12

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

micropores (microporosity)

13

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

96% inorganic
1% organic
3% water

14

What is the principal mineral component of enamel

calcium hydroxyapatite (fluro exchanged when there is fluoride present)

15

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

amelogenin

16

Enamel is the only tooth tissue that does not contain what

collagen fibers

17

How is the water distributed throughout enamel

via micropores between the crystals and proteins

18

What are the CEJ relationships

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

19

What are the different configurations of the DEJ

scalloped
smooth

20

This DEJ configuration is better adapted for occlusal forces

scalloped; in the coronal area

21

This DEJ configuration is better for non-load bearing areas

smooth; in the cervical areas

22

These are growth lines found on enamel

lines of Retzius

23

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

perikymata

24

This is the structural unit of enamel

enamel rods

25

Where are the HA crystals most dense in the enamel rod

in the center or core of the rod running parallel

26

What forms the enamel rods

ameloblast (one ameloblast = one rod)

27

This is the outer surface of the rod

enamel sheath

28

How are the HA crystals of the enamel sheath arranged

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

29

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

amelin

30

This is located between the sheath of rods

interrod substance

31

How are the HA crystals arranged in the interred substance

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

32

What create the interred substance

two or more ameloblasts

33

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

density of crystals and the direction in relation to each other

34

What are the direction of the rods compared to the dentin

they are at a 90º angle

35

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

interrod striations

36

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)

enamel lamella

37

What is the clinical significance of enamel lamella

access by acidophilic microorganisms (caries) and to stain substances

38

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

enamel tufts

39

What is the clinical significance of enamel tufts

contributes to the spread of caries at the DEJ

40

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

enamel spindle

41

What is the clinical significance of enamel spindles

contributes to the spread of caries at the DEJ

42

What makes up the enamel spindles

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

43

What are the three hypomineralized enamel structures

enamel lamella
enamel tuft
enamel spindle

44

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

Hunter-Schreager bands

45

What causes Hunter-Shreager bands

different directions of enamel rods in adjacent layers

46

What is induced by the change of enamel rod direction

functional adaptation;
minimizing the risk of cleavage in the axial direction under mastication

47

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

on the coronal most site of the DEJ