Enamel 1 Flashcards Preview

**Oral Biology > Enamel 1 > Flashcards

Flashcards in Enamel 1 Deck (77):
1

1. Is enamel Acellular or cellular?
2. Is it Vital or non-vital?
3. is it vascular or non-vascular?

1. Acellular
2. Non-vital
3. Non-Vascular

2

What is the origin of enamel?

Ectoderm

3

Enamel is the Hardest (most mineralized) tissue in the body T/F

True

4

Enamel is brittle T/F

True

5

What makes enamel dynamic?

It can be demineralized and remineralized

6

Where is enamel thickest?

At the crown, around 2.5mm

7

What is the primary component of enamel?

Hydroxyapatatite crystals

8

What is the purpose of the protein component of enamel?

Organization of crystals

9

How much of the enamel is organic material?

1%, distributed between the HA crystals

10

T/F Enamel contains collagen within the organic component

FALSE. No collagen

11

Where would you find major enamel proteins?

In the organic component

12

What are the major enamel proteins?

1. Amelogenins
2. Ameloblastins
3. Enamelin
4. Tuftelin
5. Others also exist

13

T/F some enamel proteins are present only in developing enamel

TRUE

14

How much of enamel is water?

2-3%

15

What are the 4 mineralized tissues in the body?

1. Bone
2. Dentin
3. Cementum
4. Enamel

16

What is main purpose of the tooth?

survive repeated cyclical loading

17

How are enamel crystals arranged?

Closely packed, long, ribbon like

18

Many Crystals packaged together form both the ______ and ______

1. Enamel rods
2. Interrod enamel

19

While enamel crystals are called hydrdoxyapatite, lots of enamel crystals are actually ________

Carbonatoapatite

20

How is carbonatoapatite different from hydroxyapatite?

CO3(2-) can substitute for PO4(3-), usually, but can also substitute for OH- sometimes

21

T/F enamel grows outwards, dentin is forming inwards

TRUE

22

Is the composition of enamel measure by weight or by volume

Weight

23

Hydroxyapatite can incorporate Carbonate, Magnesium, fluoride, and other ions into its structure T/F

TRUE

24

Where are carbonate and magnesium usually incorporated?

Inner enamel

25

Where is fluoride usually incorporated into enamel?

Outer enamel

26

T/F Outer enamel is more resilient in the face of an acid attack

TRUE

27

Each enamel crystal is what shape?

Hexagonal, reflective of the individual HA unit cell

28

What are the mature dimensions of enamel crystals?

Width: 60-70 nm
Thickness: 25-30 nm

29

How long is an enamel crystal?

Very long (in the mm range), it could run the entire length of the enamel layer

30

What happens to hexagonal symmetry as the crystals mature?

It increases, but fully mature crystals lose their shape somewhat

31

Enamel rods generally run perpendicular to what?

DEJ (Pulp)

32

What is an enamel rod?

Cylindrical accumulation of enamel crystals, lined up along the long axis of the rod

33

T/F Rods are straight

FALSE
**Rods are not completely straight, but curve somewhat as they progress towards the surface

34

Often rods are called _______

Prisms

**Technically they are not prisms because they are not that regular in terms of geometry

35

What is a prism?

Polyhedron with 2 polygonal bases

36

Rods are organized into ____ which run in alternating directions

Rows

37

How many ameloblasts are associated with a rod?

One ameloblast for One rod

38

T/F Orientation of enamel rods is best seen with Light microscopy

FALSE, Impossible to tell from light microscopy. Rods throw off light in all directions

39

What is the Rod Sheath?

A relatively protein rich area of enamel that surrounds the rods

40

The rod sheath runs about ___ of the way around each rod

3/4

41

For the most part, rod sheaths separate ___ and ______ enamel

1. Rod
2. Interrod

42

What happens in the areas of the Rod that are not surrounded by a rod sheath?

The enamel crystals are continuous with interrod enamel, linking the two together

43

Where is the crystal orientation in the rod not parallel to the long axis of the rods?

In the gap areas where they become continuous with interrod enamel

44

What are the rod sheath proteins?

1. Ameloblastins
2. Amelogenins

45

Rod sheaths are much more prominent in ______ _______

Higher mammals (not so much in rodents)

46

What is interrod enamel?

Same basic compositions as rods, simply different enamel crystal orientation

47

What doe interrod enamel do?

Fill the gaps between rods

48

Where is Caries though to penetrate?

Through the higher protein rod sheath areas (between rod and interrod enamel)

49

An enamel rod head is _________ to surface of enamel

Perpendicular

50

What is the composition of enamel as the ameloblasts are activated and enamel begins to be deposed?

-Only around 30% mineralized, with much larger organic component

51

As enamel matures, what happens to the organic component of enamel?

It is reduced and mineralization of enamel increases

52

What are the 3 general phases of Ameloblast maturation?

1. Pre-secretory
2. Secretory
3. Maturation

53

What is the pre-secretory phase?

Cells mature from pre-ameloblasts to ameloblasts

54

What happens in secretory phase?

Deposition of enamel

55

What is maturation phase of Ameloblasts?

Reduction of organic matrix, increase mineralization via ion transport

56

How do Ameloblasts deposit organic matrix?

Via secretory vesicles which exit the cell apically

57

Initially in the deposition of enamel, what happens to the basal lamina that separates the pre-dentin and ameloblasts?

It is penetrated by cell projections and broken down

58

Enamel is laid down directly in appostion to what?

Pre-dentin/mantle (first) dentin

59

What is Tomes' process?

-Forms during the deposition of enamel
-Projects into the developing enamel and is the site of much secretory activity

60

What is holding ameloblasts together?

Junctional complexes (terminal bars)

61

T/F Enamel has a rod arrangment even as soon as it is initially placed in appostion to dentin

FALSE, Initial enamel in apposition to dentin does not have a rod arrangement, it is uniform

62

What does Tomes' process form?

Effectively it forms the Enamel rod structure

63

What are the distal and proximal orientations of Tomes' process referring to?

Distal: Towards the forming enamel

Proximal: Towards the stratum intermedium

64

Secretion from different parts of Tomes' process forms what?

Rods, interrod enamel

65

Inner enamel epithelium in tooth development become what?

Ameloblasts

66

Trigger for ameloblasts to make proteins for enamel is what?

Formation of first pre-dentin

67

What do ameloblasts do when enamel has been laid down?

The return to being a squat cell, much like a pre-ameloblast

68

Prior to eruption what happens to enamel?

It hardens and becomes highly mineralized through the removal of water, organic material and increased HA crystal diameter

69

How long does enamel maturation take?

Relatively slow: up to 5 years for some permanent teeth

70

How much of amelognesis is maturation?

roughly 2/3

71

What is modulation?

Process by which water and proteins are removed. Fluctuations in teh distal membrane of ameloblast layers 'ruffing' and 'smoothing'

72

How do ruffles cells come to be?

-Infiltration and incorporation of calcium ions into crystals occurs during 'ruffling'
-Lowered pH perhaps favors mineralization
-Secretion of proteolytic enzymes

73

What are smooth cells?

Allow diffusion out of protein fragments out of enamel, which leak in between cells and laterally defuse through cell layer

74

What happens to the enamel organ after after enamel maturation?

The remains of the enamel orgain are attached to the tooth until eruption at which point they fuse with the oral epithelium, forming a covering over the tooth

75

What is the primary enamel cuticle?

A mineralized coating which is the last secretory product of the ameloblasts (Perhaps the basal lamina)

76

What is the secondary enamel cuticle?

-Also called 'Dental Cuticle'
-Formed from the remains of the reduced enamel epithelium merged with the oral epithelium and is removed due to mechanical forces and what not

77

What does Nasmyth's membrane refer to?

The primary and secondary enamel cuticle together