EX1; Enamel Tissue

Question 1

True or False

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

Answer 1

False; it IS THE hardest of the tissues

Question 2

What is different about the ectodermal derived tissue that forms enamel

Answer 2

it is epithelium;

the other tissues of the tooth are connective tissue

Question 3

What is different about the mineralization stages of enamel

Answer 3

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

Question 4

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

Answer 4

finite

Question 5

True or False

Enamel is the second mineralized tissue to appear

Answer 5

True; dentin is the first

Question 6

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

Answer 6

malformations

Question 7

Enamel does not contain what compared to other tissues

Answer 7

enclosed cells; acellular, aneural, avascular, and alymphatic

Question 8

*What is the definition of enamel

Answer 8

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

Question 9

What is apatite on the Mohs mineral hardness scale

Answer 9

5

Question 10

What does enamel need to maintain its integrity

Answer 10

a wet environment

Question 11

What forces is enamel subject to

Answer 11

attrition (normal)
abrasion
erosion

Question 12

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

Answer 12

micropores (microporosity)

Question 13

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

Answer 13

96% inorganic
1% organic
3% water

Question 14

What is the principal mineral component of enamel

Answer 14

calcium hydroxyapatite (fluro exchanged when there is fluoride present)

Question 15

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

Answer 15

amelogenin

Question 16

Enamel is the only tooth tissue that does not contain what

Answer 16

collagen fibers

Question 17

How is the water distributed throughout enamel

Answer 17

via micropores between the crystals and proteins

Question 18

What are the CEJ relationships

Answer 18

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

Question 19

What are the different configurations of the DEJ

Answer 19

scalloped

smooth

Question 20

This DEJ configuration is better adapted for occlusal forces

Answer 20

scalloped; in the coronal area

Question 21

This DEJ configuration is better for non-load bearing areas

Answer 21

smooth; in the cervical areas

Question 22

These are growth lines found on enamel

Answer 22

lines of Retzius

Question 23

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

Answer 23

perikymata

Question 24

This is the structural unit of enamel

Answer 24

enamel rods

Question 25

Where are the HA crystals most dense in the enamel rod

Answer 25

in the center or core of the rod running parallel

Question 26

What forms the enamel rods

Answer 26

ameloblast (one ameloblast = one rod)

Question 27

This is the outer surface of the rod

Answer 27

enamel sheath

Question 28

How are the HA crystals of the enamel sheath arranged

Answer 28

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

Question 29

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

Answer 29

amelin

Question 30

This is located between the sheath of rods

Answer 30

interrod substance

Question 31

How are the HA crystals arranged in the interred substance

Answer 31

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

Question 32

What create the interred substance

Answer 32

two or more ameloblasts

Question 33

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

Answer 33

density of crystals and the direction in relation to each other

Question 34

What are the direction of the rods compared to the dentin

Answer 34

they are at a 90º angle

Question 35

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

Answer 35

interrod striations

Question 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)

Answer 36

enamel lamella

Question 37

What is the clinical significance of enamel lamella

Answer 37

access by acidophilic microorganisms (caries) and to stain substances

Question 38

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

Answer 38

enamel tufts

Question 39

What is the clinical significance of enamel tufts

Answer 39

contributes to the spread of caries at the DEJ

Question 40

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

Answer 40

enamel spindle

Question 41

What is the clinical significance of enamel spindles

Answer 41

contributes to the spread of caries at the DEJ

Question 42

What makes up the enamel spindles

Answer 42

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

Question 43

What are the three hypomineralized enamel structures

Answer 43

enamel lamella enamel tuft enamel spindle

Question 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

Answer 44

Hunter-Schreager bands

Question 45

What causes Hunter-Shreager bands

Answer 45

different directions of enamel rods in adjacent layers

Question 46

What is induced by the change of enamel rod direction

Answer 46

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

Question 47

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

Answer 47

on the coronal most site of the DEJ