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Craniofacial Embryology > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

What is the anatomical crown?

A

The part of the tooth that is covered by enamel

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2
Q

What is the clinical crown?

A

Part of the tooth exposed above the gingiva

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3
Q

What is the hardest part of the body? Second hardest?

A

Enamel. Dentin

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4
Q

About what percentage of enamel is composed of minerals? Percentage of dentin? Percentage of cementum?

A

Enamel is about 96% mineral.
Dentin about 70% mineral.
Cementum is about 45-60% miineral

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5
Q

What is the hardness of enamel similar to?

A

Mild steel

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6
Q

Is enamel malleable?

A

No it is not malleable, it is brittle

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7
Q

Why does dentin influence the color of enamel?

A

Because enamel is translucent and the underlying dentin tends to be yellow

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8
Q

What mineral is enamel mostly made of?

A

An apatite of calcium phosphate

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9
Q

What other minerals may be incorporated into enamel during its formation?

A

Strontium, magnesium, lead and fluoride

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10
Q

How can water and dissolved ions still be absorbed into mature enamel?

A

The slightly porous enamel, due to its crystalline organization, allows some water absorption

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11
Q

What are apatites?

A

Various chemical forms of calcium phosphate and other elements

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12
Q

Of the three common apatites in enamel, which is most common?

A

Hydroxyapatite

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13
Q

What concentration of chronic fluoride ingestion may cause flurosis? What is the recommended concentration of fluoride in drinking water?

A

5 ppm.

.7 to 1.2 ppm

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14
Q

What are enamel rods?

A

Hydroxyapatite crystals of enamel are organized into long, thin rods, sometimes called prisms.

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15
Q

How long can enamel rods be?

A

As long as the entire thickness of the enamel layer

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16
Q

What are enamel rods surrounded by?

A

By interlocking additional hydroxyapatite crystals

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17
Q

What are the three typical patterns of acid-etched enamel?

A

Rod preferentially eroded
Interrod preferentially eroded
Indiscriminate erosion

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18
Q

What type of force does the irregular shape of the DEJ help to resist?

A

Shearing force

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19
Q

What are enamel lamellae?

A

Linear defects that can span the full thickness of enamel

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20
Q

What are enamel lamellae filled with?

A

Organic material from trapped pieces of the enamel organ or CT surrounding the developing tooth

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21
Q

What are enamel tufts?

A

Higher concentration of enamel protein that projects a short distance from the DEJ into the enamel

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22
Q

What are enamel spindles?

A

Left over pieces of odontoblasts that extend into the ameloblast epithelium and become trapped there as enamel begins to form

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23
Q

Is dentin a living tissue?

A

Yes

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24
Q

What do the odontoblasts remain attached to throughout the life of the tooth?

A

DEJ

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25
Q

In which direction do odontoblasts grow from the DEJ?

A

To the pulp chamber

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26
Q

Why does the size of the pulp chamber and root canal become smaller with age?

A

Dentin continues to grow into the pulp

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27
Q

What are odontoblasts nourished by?

A

Blood vessels in the pulp

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28
Q

The odontoblasts processes extend to the DEJ via what structure?

A

Dentinal tubule

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29
Q

About how many tubules are there per square mm of dentin?

A

59,000-76,000

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30
Q

What is the name of newly deposited dentin?

A

Predentin

31
Q

What kind of dentin makes up most of the tooth?

A

Primary dentin

32
Q

What is secondary dentin?

A

Dentin that develops after root formation is complete. Proceeds slowly and reduces the size of the pulp cavity

33
Q

What is mantle dentin?

A

Dentin that forms under the enamel of the crown

34
Q

What is tertiary dentin?

A

Dentin that is produced locally in response to caries, attrition and dental restoration

35
Q

What are the two subclasses of tertiary dentin?

A

Reactionary dentin and Reparative dentin

36
Q

How is reactionary dentin formed? Reparative dentin?

A

It is deposited by existing odontoblasts.

Reparative dentin is deposited by newly differentiated odontoblasts

37
Q

T/F The boundaries of dentinal tubules are established by a meshwork of collagen fibrils

A

True

38
Q

What are the three possible mechanisms of dentin sensitivity?

A
  1. Dentin is directly innervated
  2. Odontoblasts act as receptors
  3. Fluid movement through tubules stimulates receptors in pulp
39
Q

Which of the three dentin sensitivity theories is the best supported hypothesis?

A

The Fluid Movement Through Dentinal Tubules theory

40
Q

Does cementum have blood supply?

A

No, it is avascular

41
Q

Cementum is similar to what connective tissue?

A

Bone

42
Q

What are cells that produce cementum called?

A

Cementoblasts

43
Q

What do cementoblasts look like?

A

Fibroblasts

44
Q

What are mature cementoblasts called? What do the look like?

A

Cementocytes. Look like osteocytes.

45
Q

What are the four categories into which cementum is classified?

A

Acellular
Cellular
Mixed - alternating layers of acellular and cellular
Acellular Afibrillar

46
Q

Which cementum type is also called the primary? Which one is also called secondary?

A

Acellular is also primary

Cellular is also Secondary

47
Q

What is the origin of fibers of acellular cementum? What is its location on a tooth?

A

Extrinsic fiber origin.

Cervical margin to 2/3 down towards the apex

48
Q

What is the function of acellular cementum?

A

Anchorage to PDL

49
Q

What is the origin of fibers of cellular cementum? What is its location on a tooth?

A

Intrinsic fiber origin

Located in the periapical and interradicular (furcations) regions

50
Q

What is the function of cellular cementum?

A

Adaptation to tooth wear and movement and repair

51
Q

What is the granular layer of Tomes?

A

Thought to be a mix of collagen and non-collagenous matrix proteins at the dentin-cementum interface

52
Q

Which teeth often only have the acellular cementum?

A

Incisors and canines

53
Q

Why is Acellular Extrinsic Fiber Cementum (AEFC) called “acellular”?

A

Because the cementoblasts remain on the surface of the the cementum proximal to the PDL

54
Q

Why is AEFC called “extrinsic”?

A

Because the cementoblasts secrete primarily noncollagenous matrix proteins that mix with the collagen fibers produced by fibroblasts of the PDL

55
Q

What is one noncollagenous protein produces by AEFC?

A

Osteoponin

56
Q

What is the mineralization of cementum regulated by?

A

Regulated by noncollagenous matrix proteins such as osteoponin

57
Q

Cellular Intrinsic Fiber Cementum (CIFC) is produced by what kind of cementoblasts?

A

By cementoblasts that produce collagen fibrils into newly produced and unmineralized dentin of tooth roots

58
Q

At what point in the formation of the tooth root does CIFC form?

A

After at least half of the root is formed

59
Q

Which cementum type is produced during wound healing and regeneration of tissues?

A

CIFC

60
Q

What is the layer of unmineralized matrix on the surface of the CIFC called?

A

Cementoid

61
Q

What happens to the cementoid as it matures?

A

It becomes mineralized with calcium and entraps cementoblasts that also mature into cementocytes

62
Q

These entrapped “intrinsic” cementocytes have reduced ______ function

A

secretory

63
Q

What do the intrinsic cementocytes grow towards the vascular PDL?

A

Thin processes

64
Q

Where is the cementum relative to the enamel in the majority of the cementoenamel junctions?

A

In 60% of the cases cementum overlaps the enamel

65
Q

If the enamel does not overlap the enamel at the cementoenamel junction then how else does it lie relative to the enamel?

A

In 30% of the cases the cementum merely abuts with the superior enamel.
In 10% of the cases insufficient cementum actually does not join with the enamel and leaves root dentin exposed

66
Q

What are the two principal cells in the pulp of a tooth What other cells may be found in the pulp?

A

Odontoblasts and fibroblasts.

Other cells include undifferentiated (stem cells) ectomesenchymal cells, macrophages, and leukocytes

67
Q

In the pulp, where are the odontoblasts localized?

A

Next to the dentin

68
Q

What are the four zones of the pulp?

A
  1. Odontoblastic zone
  2. Cell-free zone
  3. Cell-rich zone
  4. Pulp core

Mnemonic: Old Celery Creates Pus

69
Q

What is the odontoblastic zone composed of?

A

The cell bodies of odontoblasts

70
Q

Where does the cell-free zone lie in the pulp?

A

It lies between the odontoblast bodies and a relatively dense region of fibroblasts

71
Q

What is the cell-free zone composed of?

A

Loosely arranged CT fibers and ECM

72
Q

What does the cell-rich zone consist of?

A

Fibroblasts, leukocytes, and stem cells

73
Q

The pulp core itself consists of what?

A

Blood vessels and nerves

74
Q

What are the blood vessels and nerves of the pulp core suspended in?

A

A gelatinous CT matrix

Craniofacial Embryology (10 decks)

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