Enamel Tissue: Histologic Structure and Clinical Considerations

Question 1

what is the hardest mineralized tissue in the body

Answer 1

Enamel

Question 2

what part of the tooth is not a connective tissue

Answer 2

Enamel

Question 3

what is enamel derived from

Answer 3

from specialized epithelial cells from the ectoderm

Question 4

what is the cell that makes enamel

Answer 4

Ameloblasts

Question 5

what stage doe enamel lack that other mineralized tissues have

Answer 5

No unmineralized or preenamel formation stage

Question 6

stages of enamel growth

Answer 6

Immature stage (partially mineralized)
Mature stage (fully mineralized)

Question 7

when is enamel formed

Answer 7

The second mineralized fissue in the tooth(after dentin)

Question 8

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

Answer 8

No collagen fibers

Question 9

what is enamel tissue

Answer 9

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

Question 10

what is the most clinically significant part of the tooth

Answer 10

Enamel

Question 11

what is enamel equal to hardness in

Answer 11

Mild steel

Question 12

what is the mohs mineral hardness of apatite

Answer 12

5

Question 13

when is Enamel brittle

Answer 13

when no dentin support

Question 14

why is enamel translucent

Answer 14

Thinness

Question 15

Hue of enamel depends on

Answer 15

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

Question 16

what is needed for enamel to maintain its integrity

Answer 16

Wet environment

Question 17

what is the form of tooth wear that is normal

Answer 17

Attrition

Question 18

what causes attrition

Answer 18

Slow wearing away of tooth substance under the stress of mastication

Question 19

what causes abrasion

Answer 19

Non-normal wear

Question 20

what causes erosion

Answer 20

Chemicals (see acid erosion)

Question 21

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

Answer 21

Micro porosity

Question 22

what on the pore walls can lead to carious lesions

Answer 22

Electrochemical effects

Question 23

when mineral is returned to the molecular strucutre via saliva

Answer 23

Remineralization

Question 24

when does cavitation occure

Answer 24

when demineralization exceedes remineralization

Question 25

what makes up enamel by wieght

Answer 25

96% Inorganic 1% organic 3% water

Question 26

what is the inorganic substance of enamel

Answer 26

Hydroxyappatie crystals

Question 27

what separates Hydroxyapetite in enamel vs other mineralized tissue

Answer 27

``` Larger more impurities (fluoride, carbonate) ```

Question 28

what makes up 90% of the organic substance of enamel

Answer 28

Amelogenin

Question 29

roll of Amelogenin for enamel

Answer 29

Seed protein for normal mineralization

Question 30

how are enamel proteins arranged

Answer 30

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

Question 31

how is water distributed in the enamel

Answer 31

Micropores between crystals and proteins

Question 32

what does the water form around the crystals in enamel

Answer 32

Hydration shell

Question 33

importance of hydration shell in enamel

Answer 33

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

Question 34

what happens to enamel as you age

Answer 34

``` Wears slowly (attrition) darkens Composition changes reduced porosity systemic age changes ```

Question 35

ageing reduces porosity which means

Answer 35

Reduced susceptibility to cares

Question 36

what does the composition of enamel change as you age

Answer 36

Fluoride increases

Question 37

where is the DEJ scalloped

Answer 37

Coronally

Question 38

why is the DEJ scalloped coronally

Answer 38

Adaptation to occlusial forces

Question 39

where is the DEJ smooth

Answer 39

Cervical non-load bearing areas

Question 40

what is the most common CEJ relationship

Answer 40

Cementum overlaps enamel

Question 41

what is the second most common CEJ relationship

Answer 41

Cementum meets enamel

Question 42

what is the least commone CEJ relationship

Answer 42

Does not meet enamel

Question 43

how consistent are CEJ relationships

Answer 43

Can vary even on different sides of the tooth

Question 44

What are the GRowth lines of enamel

Answer 44

Strae of Retzius

Question 45

the numerous small transverse ridges on the exposed surface of enamel

Answer 45

Perikymata

Question 46

what forms the PErikyma

Answer 46

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

Question 47

how long does it take for each perikyma to form

Answer 47

8-10 days

Question 48

The structural unit of enamel

Answer 48

Enamel rods

Question 49

size of enamel rods

Answer 49

diamter of 5-6 micrometers | length of 2.5 mm(wavey)

Question 50

where are Hydroxyapatite crystals are more dense in the enamel rods

Answer 50

the center or core of the rod

Question 51

what direction do enamel rodscrystals run

Answer 51

PArallel to the long axis of the rod

Question 52

How Many Ameloblasts form each anemal rod

Answer 52

1 ameloblast

Question 53

what is the outer surface of an enamel rod

Answer 53

Enamel sheath

Question 54

density of crystal in the enamel sheath

Answer 54

less dense (more organic substance)

Question 55

what direction do enamel crystals run in the enamel sheath

Answer 55

different directions

Question 56

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

Answer 56

Amelin

Question 57

what is the stuff between sheaths of the enamel rods

Answer 57

Interrod substance

Question 58

density of the cystals of the interrod substance

Answer 58

More dense that the sheath

Question 59

what direction do the crystals of the interrod substance rub

Answer 59

In a different direction that those of the sheath

Question 60

how many ameloblasts secrete interrod substance

Answer 60

2+

Question 61

why are enamel rods wavy

Answer 61

For strength yo

Question 62

why are enamel rods segnemented

Answer 62

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

Question 63

what direction do enamel rods lie in relation to the dentin

Answer 63

at a right angle

Question 64

where do Enamel lamella extend

Answer 64

Extend in varying depths from the surface of enamel

Question 65

what are Enamel Lamella filled with

Answer 65

Enamel protein | ORganic debris from the oral cavity

Question 66

Clinical significance of enamel lamella

Answer 66

Can cary acidophhilic microorganisms for caries | Stain substances

Question 67

where do Enamel tufts extend from

Answer 67

From the DEJ for a short distance into enamel

Question 68

what is found in an enamel tuft

Answer 68

A greater concentration of enamel protein

Question 69

Clinical significance of an enamel tuft

Answer 69

Contribute to the spread of caries at the DEJ

Question 70

where do enamel spindles extend from

Answer 70

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

Question 71

Clinical significance of an enamel spindle

Answer 71

Contribute to the spread of caries along the DEJ

Question 72

How do enamel spindles form

Answer 72

Odontoblast shoot processes between the ameloblasts. | When dentin and enamel formation begins the process become embedded in the new enamel

Question 73

what are Hunter-schreager brnads

Answer 73

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

Question 74

What causes the Hunter-Schreager bands to form

Answer 74

Different direction of enamel rods in adjacent layers

Question 75

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

Answer 75

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

Question 76

what forms the ameloblasts

Answer 76

Inner epithelial cells of the enamel organ

Question 77

what forms the Odontoblasts

Answer 77

peripheral cells of the dnetal papilla

Question 78

where does Odontoblast and ameloblast differentiation occur first

Answer 78

At the more coronla site of the future DEJ

Question 79

what type of cell are ameloblasts

Answer 79

Columnar epithelail cells

Question 80

what are Enamel pearls

Answer 80

Ectopic enamel formation

Question 81

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

Answer 81

Later in the pregnancy

Question 82

what causes mulberry molars

Answer 82

Congenital syphilis