Oucod Oral Histology Lecture 2 Enamel

Front 1

What is the hardest substance in the body?

Back 1

enamel

Front 2

Enamel is (cellular/acellular) and is mostly devoid of ____________.

Back 2

acellular, organic material

Front 3

What accounts for 96% of enamel?

Back 3

hydroxyapatite

Front 4

What are the percentages of water and organic material in enamel?

Back 4

3%; 0.5-1%

Front 5

10% HCl will result in _____________ of the enamel?

Back 5

decalcification

Front 6

What is the basic structural unit of enamel?

Back 6

enamel rods

Front 7

The organic component of enamel is what percent protein?

Back 7

90-95%

Front 8

What are the two major proteins in enamel?

Back 8

enamelin and amelogenin

Front 9

Ground substance of enamel is composed of what three substances?

Back 9

1. polysacchrides
2. glycoproteins
3. phospholipids

Front 10

the length of an enamel rod depends on its location in the ___________?

Back 10

crown

Front 11

T or F: the length of an enamel rod may exceed the thickness of the enamel

Back 11

true

Front 12

average enamel is rod is ________ in length and __________ in width?

Back 12

2mm, 5um

Front 13

rods are thicker towards the (surface/DEJ)?

Back 13

surface

Front 14

What portion of the enamel rods are wavy?

Back 14

first 1/3 of the enamel rods (near DEJ)

Front 15

enamel rod density is higher at the DEJ or surface of the tooth?

Back 15

DEJ

Front 16

Daily deposition of enamel results in what structure?

Back 16

cross striations

Front 17

a cross section of an enamel rod has what shape?

Back 17

key-hole

Front 18

enamel rods consist of what two regions?

Back 18

head and tail

Front 19

enamel rod sheaths are distinct around _____________ but blurred around _____________?

Back 19

the head, tails

Front 20

enamel rods are (parallel/perpendicular) to the long axis of the tooth, while interrod enamel is (parallel/perpendicular).

Back 20

parallel, perpendicular

Front 21

Interrod enamel is (more/less) mineralized than enamel rods.

Back 21

less

Front 22

Lack of a Tome's process will result in what kind of enamel?

Back 22

prismless

Front 23

Tome's process pit produces the rod _______?

Back 23

head

Front 24

__ ameloblasts make a core, but __ make a tail?

Back 24

1,3

Front 25

____________ is randomly dispersed the a tome's process while ___________ is not.

Back 25

amelogenin, enamelin

Front 26

_______________ serves as a template for HA deposition in enamel?

Back 26

enamelin

Front 27

T or F: maturation of enamel involves the addition in number of HA crystals?

Back 27

False, number and length do not change, only width of the crystals.

Front 28

Removal of what protein allows HA crystal to increase in size?

Back 28

amelogenin

Front 29

Name two places where prismless enamel occurs?

Back 29

DEJ, surface

Front 30

HA crystal in the enamel rod are arranged parallel to the _____________ of the rod.

Back 30

long axis

Front 31

HA crystals in the rod tail are arranged ____________ to the rod.

Back 31

obliquely

Front 32

Interrod enamel is located between a rod ______ and a rod ______?

Back 32

head, tail

Front 33

greatest amount of matrix in enamel is found in the _______________?

Back 33

enamel rod sheath

Front 34

enamel rod sheath is approx. _____ um in width?

Back 34

0.2

Front 35

The only way to distinguish between enamel rod head and rod sheath by determining the amount of ______________________?

Back 35

matrix and calcification

Front 36

Enamel rod ______ is almost exclusively HA crystals while the enamel rod _______ is almost exclusively matrix.

Back 36

head, sheath

Front 37

name the 3 zones of an enamel HA crystal.

Back 37

1. hydration shell
2. crystal surface
3. cyrstal interior

Front 38

The hydration shell on an HA crystal is formed on the outside of what layer?

Back 38

crystal surface by incorporation of water

Front 39

Which layer of an HA crystal interacts with ions?

Back 39

crystal surface

Front 40

Most ions which interact with the crystal surface of an HA crystal (soften/harden) the enamel? The exception is (Na, Mg, F, Sr, Ra, CO3, citrate)?

Back 40

soften, F

Front 41

An HA crystal is _____nm thick x ___nm wide x ____um long?

Back 41

30,65,2

Front 42

space between HA crystal is less than ___ nm?

Back 42

2

Front 43

Enamel runs ____________ at the DEJ, ____________ in the middle zone and ______________ in the outer zone.

Back 43

perpendicular, helically, perpendicular

Front 44

Enamel appears wavy in the 1/3 portion nearnest the (DEJ/surface of the tooth)?

Back 44

DEJ

Front 45

______________ are regions in enamel where groups of enamel rod curve up and out while others curve in and down.

Back 45

Hunter Schreger bands

Front 46

Hunter Schreger bands appear as ______ and _______ bands within the enamel.

Back 46

light, dark

Front 47

If you were to section a tooth longitudinally, what band would you see in the enamel? How would they appear?

Back 47

Hunter Schreger bands; you would see some bands coming towards you and some running longitudinally

Front 48

More organic content allows (more/less) light to penetrate the structure?

Back 48

more

Front 49

T or F: enamel lamellae extend the length of the enamel?

Back 49

True

Front 50

Enamel lamellae are ____________ mineralized enamel?

Back 50

improperly

Front 51

What are A, B and C?

Back 51

A - lamella
B - tuft
C - spindle

Front 52

Name the 3 causes of enamel lamella formation.

Back 52

1. Uncalcified enamel
2. crack formed and filled with enamel organ cells (before eruption)
3. crack formed after eruption and filled with salivary proteins

Front 53

T or F: enamel lamellae are more common with age?

Back 53

True, due to unequal loading on teeth

Front 54

T or F: enamel tufts extend the whole length of the enamel.

Back 54

False, they extend only through the inner 1/3

Front 55

Enamel tufts are (normal/abnormal) structures in enamel?

Back 55

normal

Front 56

Enamel tufts are (more/less) calcified than surrounding enamel?

Back 56

less

Front 57

Enamel tufts increase the organic content of enamel near the DEJ to _x other enamel?

Back 57

3

Front 58

Enamel tufts have a __________ appearance.

Back 58

grass-like

Front 59

"Leaves" of the enamel tufts are due to the _______________?

Back 59

curvature of enamel in this region

Front 60

Tension planes will cause (increased/decreased) calcification?

Back 60

decreased

Front 61

An enamel spindle is an ___________ ___________ that gets stuck in enamel.

Back 61

odontoblastic process

Front 62

DEJ is ____________ (shape) with (concave/convex) portion towards the DEJ?

Back 62

scalloped;concave

Front 63

The number of concavities in the DEJ roughly corresponds with the number of what?

Back 63

enamel rods

Front 64

cross striations are in (enamel/dentin)?

Back 64

enamel

Front 65

cross striations are (parallel/perpendicular) to enamel rods?

Back 65

perpendicular

Front 66

cross striations represent the ________ growth increment and are approx. __ - __ um apart?

Back 66

daily; 4,5

Front 67

Cross striations are synonamous with what what lines in dentin?

Back 67

inbricaiton lines of von Ebener

Front 68

Cross striations have dark and light lines. Dark lines represent areas of (more/less) calcification?

Back 68

less

Front 69

Stria of Retzius are due to _______?

Back 69

stress

Front 70

Stria of Retzius are formed because of a retraction of ______ ____________?

Back 70

tome's process

Front 71

Stria of retzius formed at birth is called a _________________?

Back 71

neonatal line

Front 72

Stria of retzius are (more/less) calcified than surrounding enamel?

Back 72

less (dark = less)

Front 73

Perikymata are surface manifestations of _____________?

Back 73

stria of retzius

Front 74

Perikymata are interspersed __________ and _______ and are located near the ______ of the tooth?

Back 74

grooves, ridges; cervix

Front 75

T or F: perikymata will eventually wear down?

Back 75

True

Front 76

T or F: Gnarled enamel is present near the DEJ?

Back 76

False, it is found in cuspal regions

Front 77

T or F: Gnarled enamel may extend through entire enamel region?

Back 77

True

Front 78

Gnarled enamel (strengthens/weakens) the tooth structure?

Back 78

strengthens

Front 79

Enamel in pits and fissures is (stronger/weaker) than at the cusps?

Back 79

weaker

Front 80

Ameloblasts often cannot complete maturation of the enamel in pits and fissures due to?

Back 80

crowding and strangulation

Front 81

Margins of restorations should be placed in (gnarled/non-gnarled enamel)?

Back 81

non-gnarled (good luck!)

Front 82

Precarious enamel lesions involve the dissolution of what part of the enamel?

Back 82

crystal cores

Front 83

In carious lesions the length of the enamel crystals is ____________ but it it isn't in precarious lesions.

Back 83

shortened

Front 84

Etching of enamel preferentially dissolves enamel rod ________?

Back 84

head (core)

Front 85

When enamel is etched, what can fill the areas of dissolved enamel?

Back 85

restorative material (composite)

Front 86

Etching will not roughen enamel surface where the enamel is ____________?

Back 86

prismless