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microanatomy > dentin (UNIT 4) > Flashcards

dentin (UNIT 4) Flashcards

1
Q

What is the organic matrix composition of dentin?

A

30% organic matrix
- Including 20% proteins and collagen type I
- 10% water.

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2
Q

What is the inorganic matrix composition of dentin?

A

70% inorganic matrix
- hydroxyapatite (calcium phosphate).

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3
Q

What is the first phase of dentinogenesis?

A

Cytodifferentiation – the formation of odontoblasts.

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4
Q

What is required to make dentin?

A

Odontoblasts

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5
Q

What is the second phase of dentinogenesis?

A

Predentin formation- Secretion of the organic matrix

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6
Q

What happens during the second phase, predentin formation?

A

The organic matrix, including collagen I fibers, is secreted, and it is called “predentin.”

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7
Q

What is the third phase of dentinogenesis?

A

Mineralization- Making the tissue hard

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8
Q

What occurs in the third phase of dentinogenesis, mineralization?

A

Hydroxyapatite (calcium phosphate) crystals are deposited onto the predentin matrix, making the tissue hard (calcification).

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9
Q

What structure determines the form of the tooth root?

A

Hertwig’s Epithelial Root Sheath (HERS), formed from the elongation of the cervical loop.

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10
Q

When does dentin production at the root begin?

A

When enamel reaches the cervical loop (cervix) of the tooth and proceeds inferiorly.

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11
Q

What is required for root dentin formation?

A

Hertwig’s Epithelial Root Sheath (HERS).

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12
Q

What is required for the Inner Enamel Epithelium to differentiate into a pre-ameloblast?

A

Stratum Intermedium cells.

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13
Q

What is the shape of odontoblasts?

A

columnar cells with long processes.

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14
Q

What is the origin of odontoblasts?

A

ectomesenchyme (neural crest).

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15
Q

How do odontoblasts polarize?

A

similarly to cells in the brain due to their ectomesenchymal origin.

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16
Q

How do odontoblasts compare to ameloblasts in terms of cell morphology?

A

more specialized cell morphology than ameloblasts.

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17
Q

Where do odontoblasts form a single layer of columnar cells?

A

At the pulpal surface of the Dentin-Enamel Junction.

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18
Q

What happens to odontoblast cell bodies as they secrete predentin?

A

They move away from the Dentin-Enamel Junction (DEJ), trapping their processes and terminal branches in predentin/dentin.

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19
Q

What remains after the removal of the organic matrix during dentin formation?

A

Calcified tissue around an empty tubule.

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20
Q

Where are signals to mineralize dentin secreted from?

A

From the odontoblast process.

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21
Q

Where is unmineralized predentin secreted from?

A

From the basal aspect of the odontoblast cell body.

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22
Q

What is the role of pre-odontoblasts?

A

They lay down pre-dentin, the organic matrix of dentin.

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23
Q

What happens to the odontoblast process during mineralization?

A

The cell body moves away from the mineralizing tissue, trapping the process within the mineralized tissue.

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24
Q

What is always present between mineralized dentin and odontoblasts?

A

A layer of unmineralized predentin.

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25
Q

Where is predentin located?

A

Between mineralized dentin and the odontoblasts.

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26
Q

How are dentin tubules formed?

A

Mineralization of predentin occurs around the still-living odontoblast processes, creating dentin tubules.

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27
Q

At what rate does mineralization occur compared to predentin formation?

A

same rate as predentin formation.

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28
Q

Why is there always a predentin cushion?

A

To separate the odontoblasts from the hard dentin during mineralization.

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29
Q

Intertubular

A

around the dentin tubule

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30
Q

What is found in decalcified dentin?

A

Organic matrix surrounding the odontoblast processes running in dentin tubules.

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31
Q

What is deposited on and within the collagen fibrils and ground substance in dentin?

A

Hydroxyapatite (small crystals).

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32
Q

What is found inside a dentin tubule?

A

Odontoblast process
Fluid
Fat
Mineral deposits (hydroxyapatite)
Uncalcified collagen fibers

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33
Q

What may be present in a dentin tubule besides odontoblast processes?

A

Nerve axons.

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34
Q

What happens to dentin tubules in response to injury?

A

They may become calcified to protect the remainder of the tubular contents and pulp.

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35
Q

Where do odontoblastic processes run in the dentin tubules?

A

They provide a conduit for dental caries to spread from the DEJ.

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36
Q

What happens to odontoblasts as dentin is secreted?

A

They recede into the pulp and become smaller and more packed.

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37
Q

Where are the terminal branches of the odontoblastic processes located?

A

Near the DEJ.

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38
Q

What can happen to odontoblastic processes in enamel?

A

They can get trapped in enamel, forming enamel spindles, which can be sites for caries infiltration into dentin.

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39
Q

How do dentin tubules contribute to sensory perception?

A

allow sensory perception throughout the dentin.

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40
Q

Where do nerve fibers run in dentin tubules?

A

run in the proximal aspect of some dentin tubules.

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41
Q

Do nerves extend to the DEJ?

A

No

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42
Q

Where is dentin most sensitive?

A

DEJ

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43
Q

What causes pain in dentin?

A

All stimuli result in pain, which may be explained by fluid movement through the tubules.

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44
Q

What types of sensations does dentin respond to?

A

Dentin is sensitive to temperature and chemicals, but all sensations translate to pain.

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45
Q

Where do nerve fibers run in dentin tubules?

A

proximal aspect of some dentin tubules.

46
Q

What are the 3 ways to name different types of dentin?

A

Mantle, Circumpulpal
Primary, Secondary
Peritubular, Intertubular.

47
Q

Based on location and timing

A

Mantle
Circumpulpal

48
Q

What is Mantle Dentin?

A

The initial layer of dentin, adjacent to enamel, hypomineralized.

49
Q

What does Mantle Dentin explain in caries?

A

It explains the spread of caries at the DEJ.

50
Q

What is Circumpulpal Dentin?

A

Dentin around the pulp, better calcified, forms after mantle dentin.

51
Q

How does Circumpulpal Dentin compare to Mantle Dentin?

A

Circumpulpal is better calcified and forms the bulk of the dentin.

52
Q

Where is Mantle Dentin located?

A

It is located in the crown of the tooth, replacing the basement membrane at the DEJ.

53
Q

What is unique about Mantle Dentin?

A

only found in the crown of the tooth.

54
Q

What type of collagen fibrils are found in Mantle Dentin?

A

large and irregular collagen fibrils

55
Q

What type of collagen fibrils are found in Circumpulpal Dentin?

A

smaller, regular collagen fibrils.

56
Q

What is Globular Mineralization?

A

The production of globules of dentin that fuse together.

57
Q

What happens if globules of dentin fail to completely fuse?

A

It leaves a layer of interglobular dentin that is hypocalcified, lacking peritubular dentin.

58
Q

What is Linear Mineralization?

A

A continuous front of mineralization, roughly parallel to the odontoblastic layer.

59
Q

What is Interglobular Dentin?

A

occurs when globules of dentin fail to fuse completely, resulting in incomplete calcification (hypomineralization).

60
Q

What causes interglobular dentin?

A

Incomplete fusion of dentin globules, leading to areas of hypomineralization.

61
Q

Where is interglobular dentin primarily found?

A

Mainly in the crown near the DEJ, between the mantle and circumpulpal dentin.

62
Q

What is the mineralization status of interglobular dentin?

A

hypocalcified (less mineralized)

63
Q

How is interglobular dentin formed?

A

ncomplete globular mineralization, where globules of dentin fail to fully fuse.

64
Q

What is Tomes’ granular layer?

A

It is a layer of dentin found in the root, characterized by areas of hypocalcification.

65
Q

What might cause Tomes’ granular layer?

A

Possibly caused by the looping pattern of dentinal tubules or the arrangement of collagen fibers

66
Q

Where is Tomes’ granular layer located?

A

It is located in the root of the dentin.

67
Q

What characterizes Tomes’ granular layer?

A

Areas of hypocalcification within the dentin.

68
Q

What is Tomes’ granular layer?

A

A thin layer of dentin adjacent to the cementum.

69
Q

How is Tomes’ granular layer characterized?

A

It is hypocalcified, meaning it is less mineralized.

70
Q

Is Tomes’ granular layer continuous with any other dentin?

A

Yes, it is continuous with mantle dentin, which is only found in the crown.

71
Q

What is linear mineralization?

A

occurs throughout the remainder of circumpulpal dentin formation, where small islands of dentin form and fuse along a continuous front.

72
Q

How does the front of linear mineralization progress?

A

The front of mineralization roughly parallels the odontoblast layer.

73
Q

What is the pattern of dentin formation in linear mineralization?

A

Small islands of dentin form and fuse along the continuous front, creating a steady, linear progression.

74
Q

How do dentin tubules appear in the crown?

A

‘S’ shaped course in the crown.

75
Q

How do dentin tubules appear in the root?

A

straighter course in the root.

76
Q

How can a lesion of dentin affect the dental pulp?

A

local effect on the dental pulp at a more apical level than at which the insult occurred.

77
Q

What happens if a pigmented endodontic filling leaks?

A

A pigmented endodontic filling placed below the cervix may leak back up dentinal tubules and show up on the occlusal surface.

78
Q

How do dentin tubules appear near the DEJ?

A

branches have smaller diameters (2 µm) and more space to spread out.

79
Q

How do dentin tubules appear closer to the pulp cavity?

A

larger diameters (3-4 µm) and are closely packed.

80
Q

Based on when it is formed: before or after tooth eruption and in response to damage

A

Primary
Secondary

81
Q

When is primary dentin formed?

A

before tooth eruption and includes mantle and part of circumpulpal dentin.

82
Q

When is secondary dentin formed?

A

after tooth eruption and is deposited very slowly. It is always circumpulpal dentin.

83
Q

Is circumpulpal dentin part of primary or secondary dentin?

A

is part of both primary and secondary dentin.

84
Q

What are the incremental lines of von Ebner?

A

thin, transverse bands at right angles to the dentinal tubules, marking daily growth patterns of dentin.

85
Q

What do the incremental lines of von Ebner indicate?

A

They demarcate the daily growth patterns of dentin

86
Q

What are the contour lines of Owens?

A

dark bands across dentinal tubules that show reduced mineralization (hypocalcified).

87
Q

What causes the formation of contour lines of Owens?

A

They are produced by systemic disturbances in dentin growth, such as birth (neonatal line) and fever.

88
Q

Based on location compared to the dentin tubule

A

Peritubular
Intertubular

89
Q

Where is intertubular dentin located

A

Between dentin tubules

90
Q

When is intertubular dentin formed

A

formed during normal dentin deposition.

91
Q

Where is Peritubular/Intratubular dentin located

A

adjacent to the odontoblast processes (dentin tubules)

92
Q

When is Peritubular/Intratubular dentin formed

A

formed later in life as part of aging.

93
Q

Peritubular dentin

A

Fine collagen fibers
Heavily mineralized (hypermineralized)
Susceptible to acid

94
Q

Intertubular dentin

A

Course collagen fibers
Less well calcified

95
Q

How does Peritubular Dentin compare to Intertubular Dentin in terms of mineralization?

A

much more calcified/mineralized than the surrounding Intertubular Dentin.

96
Q

What happens during decalcification of dentin?

A

Loose intratubular dentin decalcifies, leaving only the intertubular matrix and making the tubules appear much larger.

97
Q

What is Sclerotic Dentin?

A

highly mineralized and becomes transparent due to the absence of an organic matrix.

98
Q

Why does Sclerotic Dentin appear transparent?

A

It lacks an organic matrix to reflect light, allowing light to pass through without deflection.

99
Q

What happens to Sclerotic Dentin during processing?

A

It is removed during processing due to its high mineralization.

100
Q

What happens to dentin in cases of caries, attrition, abrasion, erosion, or cavity preparation?

A

In these cases, dentin may undergo changes in structure, such as increased mineralization or sclerosis.

101
Q

What is Tertiary Dentin?(Reactive and Reparative dentin)

A

forms in response to injury and helps seal off the affected area.

102
Q

What is Reactive Dentin?

A

produced by damaged preexisting odontoblasts in response to injury.

103
Q

How do the tubules in Tertiary Dentin differ from normal dentin?

A

Tubules in tertiary dentin are absent, fewer, or irregular.

104
Q

What happens to the odontoblasts in Tertiary Dentin?

A

Trapped odontoblasts in tertiary dentin degenerate.

105
Q

What is reparative dentin?

A

Reparative dentin is tertiary dentin made from newly formed odontoblasts.

106
Q

What are dead tracts in dentin?

A

empty dentinal tubules resulting from cell death of odontoblasts and attrition

107
Q

How do dead tracts in dentin rub?

A

between the DEJ or DCJ and new reparative dentin.

108
Q

How do dead tracts contribute to infection?

A

provide a pathway for infection to spread to the tooth pulp.

109
Q

What is a key feature of dentin production?

A

Dentin is produced throughout the life of the tooth and can undergo repair.

110
Q

Why does caries spread rapidly in dentin?

A

Due to the high organic content and dentin tubules connecting enamel to pulp.

111
Q

What happens when dentin is exposed?

A

Odontoblasts and processes are exposed to injury, increasing sensitivity.

112
Q

How does dentin contribute to sensory perception?

A

Dentin has nerve endings on odontoblasts, making it highly sensitive to pain and touch.

microanatomy (6 decks)

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