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tooth development Flashcards

1
Q

Primary dentition (baby teeth) begins at:

A

6-8 weeks of gestation

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2
Q

Secondary dentition (adult teeth) begins at:

A

20 week of gestation to 10th month after birth

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3
Q

Permanent molars begin at:

A

20th week of gestation to

5th year after birth (3rd molars)

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4
Q

What is ectomesenchyme?

A

A specialized connective tissue in the face derived from neural crest cells.

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5
Q

What two components interact during tooth development?

A

The ectoderm and ectomesenchyme components.

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6
Q

Which component has odontogenic potential and initiates tooth development?

A

The epithelial lining.

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7
Q

What is the role of the ectomesenchyme component in tooth development?

A

It controls subsequent stages of tooth development after initiation.

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8
Q

How do the ectoderm and ectomesenchyme components interact during tooth development?

A

They continuously interact with each other throughout the process.

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9
Q

What happens if the sequence of interactions between ectoderm and ectomesenchyme components is interrupted?

A

The process of tooth development is also interrupted.

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10
Q

Why is the interaction between ectomesenchyme and ectoderm important in tooth development?

A

Continuous interaction is essential for the proper progression of tooth development.

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11
Q

Stages of Tooth Development

A

Induction Phase

Bud Stage

Cap Stage

Bell Stage

Crown Stage

Root Stage

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12
Q

What causes the oral epithelium to proliferate into the underlying mesenchyme during dental lamina formation?

A

An increased number of cell divisions in the thickened oral epithelium.

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13
Q

What is the result of different growth rates in parts of the proliferating oral epithelium?

A

The formation of local thickenings, or buds, that develop into nearly spherical balls of epithelial cells.

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14
Q

What structure forms as a nearly spherical ball of epithelial cells during early tooth development?

A

A dental bud.

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15
Q

With what is each epithelial sphere (dental bud) associated during dental lamina formation?

A

A sphere of condensed mesenchyme.

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16
Q

What is the role of the condensed mesenchyme in relation to the epithelial sphere during dental lamina formation?

A

It interacts with the epithelial sphere to support the budding process as part of early tooth development.

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17
Q

What is the dental lamina?

A

A band of epithelial tissue that proliferates into the underlying mesenchyme, initiating the formation of tooth buds.

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18
Q

What stage of tooth development involves signaling at the enamel knot?

A

The Induction Stage.

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19
Q

During the Induction Stage, where does magical signaling occur?

A

In the ectomesenchymal cells at the enamel knot.

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20
Q

What structure initiates the signaling that leads to ectodermal cell proliferation in tooth development?

A

The dental lamina.

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21
Q

What is the result of signaling by the dental lamina during the Induction Stage?

A

Ectodermal cells start proliferating in specific, well-spaced locations to form tooth placodes.

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22
Q

What are tooth placodes?

A

Clusters of proliferating cells that mark the initial sites of future teeth.

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23
Q

Is the signaling process during the Induction Stage of tooth development fully understood?

A

No, it is still not well understood.

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24
Q

Where does the Dental Lamina development start?

A

anteriorly at the midline and proceeds posteriorly

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25
Q

What stage in tooth development follows the Induction Stage?

A

The Bud Stage.

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26
Q

During the Bud Stage, what induces epithelial cells to proliferate and start budding?

A

Signaling from neural crest cells (ectomesenchyme).

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27
Q

What does the thickening and in-growth of the oral epithelium during the Bud Stage lead to?

A

The formation of tooth buds, also known as enamel organs.

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28
Q

What are tooth buds?

A

Early structures formed during the Bud Stage that eventually give rise to teeth.

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29
Q

What is the primary role of neural crest cells during the Bud Stage?

A

To signal the epithelial cells to proliferate and form the initial tooth buds.

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29
Q

Where do the epithelial cells start budding during the Bud Stage?

A

Into the region where the neural crest cells (ectomesenchyme) are located.

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30
Q

What causes the oral epithelium to proliferate into the underlying mesenchyme during the Bud Stage?

A

An increased number of cell divisions in the thickened oral epithelium.

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31
Q

How does the proliferating epithelium change shape during the Bud Stage?

A

It thickens locally, forming nearly spherical balls or “buds” of epithelial cells.

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32
Q

What are the buds that form during the Bud Stage?

A

Nearly spherical clusters of epithelial cells that will develop into tooth structures.

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33
Q

What is each epithelial bud associated with during the Bud Stage?

A

A sphere of condensed ectomesenchyme.

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34
Q

Why do different parts of the proliferating epithelium grow at different rates during the Bud Stage?

A

This variation in growth rates leads to the formation of localized thickenings or buds.

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35
Q

What role does the condensed ectomesenchyme play in the Bud Stage?

A

It associates with each epithelial sphere, supporting the developing tooth bud.

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36
Q

Cap Stage

A

Histodifferentiation

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37
Q

What is the Cap Stage in tooth development?

A

lateral cell proliferation in the tooth bud causes the middle to invaginate (indentation shape), marking further tooth structure development.

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38
Q

What are the two types of epithelial cells formed during the Cap Stage?

A

Inner enamel epithelial cells and outer enamel epithelial cells.

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39
Q

What is the significance of the inner and outer enamel epithelial cells during the Cap Stage?

A

These cell layers will play crucial roles in forming the enamel and other parts of the tooth structure as development progresses.

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40
Q

Enamel Organ =

A

Inner enamel epithelium (IEE) + Outer enamel epithelium (OEE) + ectoderm cells

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41
Q

What forms when neural crest cells (ectomesenchyme) are encompassed by the enamel organ?

A

The Dental Papilla.

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42
Q

what forms in the dental papilla?

A

Pre-odontoblast

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43
Q

What do outer neural crest cells (ectomesenchyme) proliferate to form?

A

The Dental Follicle (Dental Sac).

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44
Q

what does the Dental Follicle/sac give rise to?

A

periodontium

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45
Q

Development of enamel organ:

A

Thickening of Inner enamel epithelium

Distinction of Inner enamel epithelium and Outer enamel epithelium

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46
Q

Tooth Germ =

A

Outer enamel epithelium + Inner enamel epithelium + Dental Papilla + Dental follicle

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47
Q

Basement membrane

A

between the Inner enamel epithelium (IEE) and the Dental Papilla

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48
Q

What major events happen during the Bell Stage of tooth development?

A

Cytodifferentiation, morphodifferentiation, disintegration of the dental lamina, enamel organs mature, and molar development.

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49
Q

What is cytodifferentiation during the Bell Stage?

A

The process where cell size and function are established.

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50
Q

What is morphodifferentiation during the Bell Stage?

A

The process where the size and shape of the tooth crown are established.

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51
Q

What happens to the dental lamina during the Bell Stage?

A

The dental lamina disintegrates and extends caudally.

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51
Q

What happens to the enamel organ during the Bell Stage?

A

It matures.

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52
Q

What is the Stellate Reticulum in tooth development?

A

A group of star-shaped cells within the body of the enamel organ.

52
Q

What do the cells in the Stellate Reticulum secrete?

A

Water-absorbing glycosaminoglycans.

52
Q

Why do the cells in the Stellate Reticulum appear star-shaped?

A

They hold onto each other through desmosomes, creating a star-like appearance.

53
Q

What forms in the stratum Intermedium.

A

ameloblasts, which are cells that create tooth enamel

53
Q

Stratum intermedium

A

flat cells line up adjacent to the inner enamel epithelium (required to induce ameloblast development from inner enamel epithelium)

54
Q

What is the role of Secondary Enamel Knots in tooth development?

A

They signal the formation of the future cusps of the teeth.

55
Q

When is the cusp form of each tooth determined?

A

Before any tissue mineralization occurs.

56
Q

What is the Successional Lamina?

A

An outgrowth of the dental lamina on the lingual side.

57
Q

What does the Successional Lamina give rise to?

A

The primordium of the enamel organ for the tooth germ of permanent teeth.

58
Q

How do the posterior molars develop compared to anterior teeth?

A

Posterior molars develop directly from the dental lamina without primary predecessors.

59
Q

What happens to the dental lamina near the 1st permanent molar?

A

It detaches from the oral epithelium and extends posteriorly as an epithelial cord.

60
Q

When do the crowns of primary and successional (permanent) teeth develop?

A

They develop at about the same time during early embryonic development.

61
Q

Do the roots of primary and successional teeth develop at the same time?

A

No, the roots of primary and successional teeth develop at very different times.

62
Q

What happens to the dental lamina during the Bell Stage?

A

It disintegrates.

63
Q

What can form from remnants of the dental lamina?

A

Epithelial pearls.

64
Q

Why do epithelial pearls form?

A

Because cells that form enamel may remain in areas where they shouldn’t be.

65
Q

What happens to the posterior-most extent of the dental lamina?

A

It does not disintegrate but instead elongates posteriorly.

66
Q

What does the posterior extension of the dental lamina give rise to?

A

The permanent molars.

67
Q

Induction Phase

A

Formation of dental lamina and determination of future tooth location.

68
Q

Bud Stage

A

Dental lamina ectoderm grow into neural crest/ectomesenchyme

69
Q

Cap Stage

A

Histodifferentiation (now it’s a tooth germ). Invagination of enamel organ into itself due to differences in growth rates of lateral (faster growth) and medial (slower growth) inner enamel epithelial (IEE) cells.

70
Q

Bell Stage

A

cytodifferentiation, morphodifferentiation, Formation of the successional lamina, disintegration of the dental lamina

71
Q

Crown Stage

A

When hard tissue is laid down

72
Q

Root Stage

A

Formation of the root

73
Q

What do pre-odontoblasts stimulate IEE cells to become?

A

Pre-ameloblasts.

74
Q

Late Bell Stage:

A

Cytodifferentiation

75
Q

Where does maturation begin in tooth development?

A

At the future cusp.

76
Q

What cells in the dental papilla face the inner enamel epithelium (IEE) and become pre-odontoblasts?

A

Ectomesenchymal cells of the dental papilla.

77
Q

What is the role of pre-ameloblasts in tooth development?

A

They stimulate the maturation of odontoblasts, which then secrete dentin.

78
Q

How does dentin production affect ameloblasts?

A

It stimulates their maturation, leading them to secrete enamel.

79
Q

What role does the elongating dental papilla play during maturation?

A

It provides nutrition to ectomesenchymal cells and the IEE.

80
Q

What happens to the ectomesenchymal cells of the dental papilla at the future cusp?

A

They line up to face the inner enamel epithelium (IEE) and become pre-odontoblasts.

81
Q

What effect do pre-odontoblasts have on inner enamel epithelial (IEE) cells?

A

They cause IEE cells to differentiate into pre-ameloblasts.

82
Q

How do pre-odontoblasts and inner enamel epithelial (IEE) cells interact in tooth development (crown stage)?

A

Pre-odontoblasts induce IEE cells to become pre-ameloblasts.

83
Q

What effect do pre-ameloblasts have on pre-odontoblasts?

A

They induce pre-odontoblasts to become full odontoblasts, which begin laying down dentin.

84
Q

What does dentin production trigger in pre-ameloblasts?

A

It causes pre-ameloblasts to become fully mature ameloblasts that start laying down enamel (with support from the stratum intermedium).

85
Q

What role does the outer enamel epithelium (OEE) play during enamel formation?

A

The OEE moves closer to the IEE to give ameloblasts access to the blood supply.

86
Q

What additional change occurs in the dental papilla during this crown stage?

A

Blood vessels begin forming in the dental papilla.

87
Q

What happens In the early crown stage?

A

dentin is laid down first followed by enamel

88
Q

How does the Dentin-Enamel Junction (DEJ) form?

A

The basement membrane that originally separated the enamel organ from the dental papilla transforms into the DEJ.

89
Q

Where does the DEJ originate?

A

It forms where the basement membrane originally separated ectodermal and ectomesenchymal tissues from the start of tooth development.

90
Q

Reduced Enamel Epithelium contents

A

Outer Enamel Epithelium

Stellate Reticulum

Stratum Intermedium

Inner Enamel Epithelium/Ameloblasts

90
Q

How does the enamel organ receive nutrients during REE formation?

A

Blood vessels in folds outside the outer enamel epithelium provide nutrients.

91
Q

Where does the formation of the REE begin?

A

At the cusp of the developing tooth.

92
Q

What happens to the Outer Enamel Epithelium (OEE) in the late Bell Stage?

A

The OEE is thrown into folds, allowing blood vessels to invade these folds from the dental follicle.

93
Q

How does the collapse of the stellate reticulum affect nutrient transport?

A

It brings blood vessels and the OEE closer to the stratum intermedium, facilitating nutrient transport.

94
Q

What effect do preameloblasts have on adjacent cells of the dental papilla?

A

They trigger these cells to elongate, contributing to further tooth development.

95
Q

How are nutrients transported to the preameloblasts?

A

Nutrients from blood vessels pass through the OEE to the stratum intermedium, which then transports them to the preameloblasts.

96
Q

What separates preameloblasts from pre-odontoblasts?

A

A thick basal lamina.

97
Q

How does the enamel organ receive its blood supply before hard tissue is laid down?

A

The enamel organ receives blood supply via blood vessels in the dental papilla.

97
Q

What happens to the blood supply to ameloblasts once hard tissue is laid down?

A

The blood vessels in the dental papilla may no longer supply the ameloblasts.

98
Q

How are ameloblasts nourished after hard tissue formation?

A

nourished by blood vessels from outside the outer enamel epithelium once the enamel organ collapses to form the reduced enamel epithelium (REE).

99
Q

Early Bell stage

A

Inner Enamel Epithelial cells differentiate into pre-ameloblasts

99
Q

Bell stage

A

Pre-ameloblasts: nuclei are located close to the basement membrane

99
Q

Crown stage

A

Ameloblasts: nuclei migrate away from the basement membrane to opposite end of the cell as it prepares to secrete enamel.

99
Q

What causes the ameloblasts’ nuclei to migrate during enamel secretion?

A

The change in blood supply location causes the ameloblasts’ nuclei to migrate from the basement membrane to the opposite end of the cell as they prepare to secrete enamel into the basement membrane.

100
Q

What does the Reduced Enamel Epithelium (REE) give rise to?

A

the attachment epithelium that binds the gingiva to the hard tissue of the tooth.

101
Q

What is the Cervical Loop in the Bell Stage?

A

The cervical loop is the reflection of the outer enamel epithelium onto the inner enamel epithelium.

102
Q

What does the cervical loop lack?

A

It lacks the stratum intermedium.

103
Q

What happens to the cervical loop during root development?

A

The cervical loop will elongate inferiorly during root development.

104
Q

What is the effect of the absence of stratum intermedium at the cervical loop?

A

prevents the development of pre-ameloblasts, altering cytodifferentiation.

105
Q

When does the crown stage end in tooth development?

A

The crown stage ends when enamel and dentin formation reaches the cervical loop.

106
Q

What is the elongation of the cervical loop?

A

Hertwig’s Epithelial Root Sheath (HERS)

107
Q

What is the role of the Inner Enamel Epithelium (IEE) in tooth development?

A

The IEE communicates with the dental papilla to create pre-odontoblasts.

108
Q

What is the Hertwig’s Epithelial Root Sheath (HERS) formed by?

A

formed by the inner and outer enamel epithelium of the cervical loop

109
Q

Why can’t the Inner Enamel Epithelium (IEE) differentiate into pre-ameloblasts without the stratum intermedium?

A

Without the stratum intermedium, the IEE cannot differentiate into pre-ameloblasts because the stratum intermedium is essential for the differentiation process.

110
Q

What happens to the Inner Enamel Epithelium (IEE) when stratum intermedium cells are absent?

A

Without stratum intermedium cells, the IEE cannot differentiate into pre-ameloblasts, and both the IEE and outer enamel epithelium (OEE) degenerate.

111
Q

What happens to the pre-odontoblasts when the IEE and OEE degenerate?

A

The pre-odontoblasts are left alone and can only produce a small amount of pre-dentin.

111
Q

What happens after the IEE and OEE degenerate?

A

Ectomesenchymal cells from the dental sac are stimulated to become cementoblasts, which secrete cementum on the dentinal surface.

112
Q

How does the cementoblast interact with the pre-odontoblast?

A

The cementoblasts communicate with the pre-odontoblasts, stimulating the pre-odontoblasts to become fully differentiated odontoblasts, which then secrete fully mineralized dentin.

113
Q

What happens to ectomesenchymal cells from the dental sac that don’t reach the dentinal surface during root formation?

A

are stimulated to become fibroblasts, which form the periodontal ligament with long tethering processes.

114
Q

What happens to ectomesenchymal cells from the dental sac that are farthest from the dentinal surface?

A

These ectomesenchymal cells differentiate into osteoblasts, which form the alveolar bone.

115
Q

What are the key roles of Hertwig’s Epithelial Root Sheath (HERS) in root formation?

A

HERS is important for guiding root formation and determining the size, shape, and number of tooth roots

116
Q

Does Hertwig’s Epithelial Root Sheath (HERS) form the root itself?

A

No, HERS does not form the root itself; it determines the shape of the root.

117
Q

What is the Epithelial Diaphragm in root formation?

A

The Epithelial Diaphragm is formed by invaginations of Hertwig’s Epithelial Root Sheath at the apex of the root.

118
Q

Epithelial diaphragm determines what?

A

determines the number of roots/tooth

119
Q

How does single root development occur?

A

In single root development, the epithelial root sheath grows apically as an epithelial cylinder from the cervical edge of the enamel organ.

120
Q

How do multiple roots form in tooth development?

A

Multiple roots occur when additional extensions of the epithelial diaphragm meet in the midline, dividing the apical foramen into two or more foramen, leading to the formation of multiple roots.

121
Q

How are root formation and tooth eruption related?

A

Root formation and tooth eruption occur simultaneously, but the location of the base of the tooth does not change during this process.

122
Q

What are some examples of congenital tooth abnormalities?

A

Congenital tooth abnormalities can include the splitting of the tooth germ or the fusion of adjacent tooth germs.

123
Q

How can trauma and infection affect tooth development?

A

Trauma and infection can affect the development of permanent teeth, leading to malformations such as variations in size, shape, number, or structure.

microanatomy (6 decks)

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