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121 Histology & Embryology > Odontogenesis > Flashcards

Odontogenesis Flashcards

1
Q

At what week does the stomodeum form? What is it derived from?

A

Begins at week six. Derived from ectoderm, lined with epithelium

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2
Q

What do dental placodes give rise to?

A

Tooth buds/enamel organs

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3
Q

What does the basement membrane separate? What does it give rise to?

A

Separates dental lamina and ectomesenchyme

Gives rise to the future Dentinoenamel Junction

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4
Q

What is embryonic connective tissue? What does it surround and give rise to?

A

Ectomesenchymal tissue

Surrounds the dental lamina in each arch and gives rise to Dental papilla (dentin/pulp) and the dental follicle (cementum/PDL/alveolar bone)

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5
Q

Where does the dental Papilla form?

A

Inside the enamel organ concavity

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6
Q

Where does the dental follicle form?

A

Around the enamel organ

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7
Q

When does tooth formation occur?

A

Weeks 6/7

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8
Q

What two types of tissue interact during the initiation stage of tooth formation?

A

Epithelial tissues and ectomesenchyme tissues

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9
Q

When does the bud stage take place? What is it surrounded by?

A

Week eight

Buds are surrounded by ectomesenchyme

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10
Q

When is the cap Stage? And what is formed during the cap stage?

A

Occurs weeks 9 to 10

Proliferation of epithelial cells form the tooth germ

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11
Q

What is the enamel organ? What are the two types of epithelium?

A

Ectodermal tissue that gives rise to tooth enamel

Outer enamel epithelium (OEE, convex) and inner enamel epithelium (IEE, concave)

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12
Q

What is the enamel knot? What is it composed of?

A

Mass of stellate reticulum cells

Signal center for cusp formation during the bell stage

Composed of an enamel cord and an enamel navel

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13
Q

What is the enamel cord?

A

String of cells running from enamel knot to the outer enamel epithelium at the enamel navel

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14
Q

What is the enamel navel?

A

Surface depression in outer enamel epithelium where the cord attaches

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15
Q

What is the cervical loop?

A

Inferior circumference of the junction of OEE and IEE and gives rise to the cervix of the tooth: future CEJ

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16
Q

What do the dental Papilla give rise to?

A

Dentin and Pulp

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17
Q

What does the dental follicle give rise to? What does it surround?

A

Gives rise to cementum, PDL and alveolar bone.

Membranous sac that forms around the enamel organ and dental Papilla

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18
Q

What does vestibular lamina form?

A

Forms the oral vestibule

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19
Q

When does the bell stage occur? What happens here?

A

Occurs during weeks 11 and 12

Morphodifferentiation and Histodifferentiation occur

The dental Papilla/Ectomesenchyme instructs the enamel Organ in how to change

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20
Q

What is morphodifferentiation?

A

Tooth shape change from cap to bell to tooth

Enamel knot signals cusp formation- cells atrophy in incisors

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21
Q

What is Histodifferentiation? Where does it primarily occur?

A

Cellular changes that occur primarily in the enamel organ

OEE changes from squamous to low cuboidal

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22
Q

What is stellate reticulum?

A

Core cells

Push apart OEE and IEE and helps form cap shape

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23
Q

What is stratum intermedium (SI)?

A

New flat layer of cells appear/form between the SR and IEE

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24
Q

What happens to IEE during histodifferentiation?

A

Cells change from squamous to tall columnar

IEE cells form pre-Ameloblasts that will give rise to enamel

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25
Q

What happens to the dental papilla during the bell stage?

A

 outer cells form preodontoblasts that will give rise to Dentin

Central cells will form the pulp

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26
Q

What happens to the dental follicle during the bell stage?

A

Forms a membrane around the entire tooth germ

Follicle will become encapsulated by bone and become either the maxilla or mandible

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27
Q

What happens to Dental lamina during the bell stage?

A

Starts to disintegrate and forms epithelial cell rests called cell rests of Serres

These proliferate posteriorly and give rise to the lamina of the permanent nonsuccedaneous molars

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28
Q

What happens to the stellate reticulum during the apposition stage?

A

It collapses

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29
Q

Which dental tissue forms first?

A

Dentin. Once Dentin forms then enamel can form

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30
Q

How are odontoblasts formed?

A

Pre-odontoblast attach to the basement membrane

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31
Q

What do the odontoblast do during the apposition stage?

A

Lay down the first layer of Dentin matrix (formed by collagen) and begin dentinogenesis

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32
Q

What is the first layer of formed Dentin called

A

Mantle Dentin

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33
Q

When do Ameloblasts form? What do they compose And what is it called?

A

After the mantle Dentin forms

Forms the first layer of enamel matrix and begins Amelogenesis

This first layer is called aprismatic enamel

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34
Q

What is aprismatic enamel?

A

First layer of formed enamel

Forms in response to dentin formation

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35
Q

What does the basement membrane get renamed as during the apposition stage?

A

Membrane performative

Disintegrates after attachment of odontoblasts and Ameloblasts

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36
Q

What forms the dentinoenamel junction?

A

Mantle Dentin and aprismatic enamel

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37
Q

What happens to the dental papilla during the apposition stage?

A

Form the dental pulp and become innervated with sensory nerves

38
Q

What happens to ameloblasts after enamel is formed?

A

The Ameloblasts die. This is why teeth cannot repair themselves

39
Q

What is dentinogenesis?

A

Dentin formation

40
Q

During what stage does dentinogenesis occur?

A

Apposition stage

41
Q

Where is mantle Dentin found? What is it formed by?

A

Found in Coronal and radicular Dentin

Formed by odontoblast and is the layer closest to the DEJ & DCJ

42
Q

What are Korff’s fibers? What type of Dentin are they found in?

A

Bushy collagen fibers, only found at the DEJ. Perpendicular to DEJ and Crown and parallel when in the root 

Only in mantle Dentin between the odontoblast

43
Q

What is the Dentin matrix formed by?

A

Odontoblasts

Collagen fibers formed around (peritubular dentin) and between (intertubular) the odontoblastic processes

44
Q

Where is Circumpulpal Dentin found?

A

In Coronal and ridicular Dentin

 no Korff’s fibers, forms all remaining Dentin and the bulk of the tooth

45
Q

What is housed in Dentin tubules?

A

Odontoblast and processes in formed Dentin. Peritubular dentin forms the tubul. and intertubular Dentin forms between the Dentin tubules

46
Q

How is calcium hydroxyapatite formed?

A

When calcium salts crystallize during the mineralization process

47
Q

Where does calcium hydroxyapatite crystallization occur?

A

At matrix vessels when they rupture and release the calcium hydroxyapatite in the Dentin matrix

48
Q

What aids in mineralization?

A

Odontoblast producing mineralizing proteins like phospholipids and Phosphophoryn

49
Q

What percentage is Dentin mineralized?

A

65 to 70%

50
Q

What is mantle Dentin?

A

First Dentin formed

Closest to the DEJ & DCJ

Mantle Dentin always next to Junction with Enamel

51
Q

What is Circumpulpal Dentin?

A

All remaining Dentin right up to the pulp

52
Q

What is peritubular Dentin?

A

Forms Dentin tubules, highly calcified

53
Q

What causes Dentin sensitivity?

A

Dentin is perforated and has channels. When recession occurs this portion is exposed and sensitivity can occur

54
Q

What is inter-tubular Dentin?

A

Forms between the tubules, a little less calcified

55
Q

What is pre-Dentin?

A

Newest formed, non-mineralized Dentin matrix. Closest to the pulp

Made from collagen

56
Q

What is coronal Dentin?

A

Dentin of the crown, forms before ridicular Dentin and contains the DEJ

57
Q

What is radicular Dentin?

A

Dentin of the root, last to form after coronal and contains the DCJ

58
Q

What is amelogenesis?

A

Enamel formation

59
Q

What is Tome’s process?

A

Very end of the ameloblast, creates a rod space

60
Q

What is the enamel matrix?

A

Formed by ameloblasts

Step 1: ameloblasts retreat, Tome’s process creates rod space/substance

Step 2: rod space back-filled with more matrix forming rod segment

61
Q

What are rod segments? What are they created by?

A

Increments of formed enamel matrix

Created by 4 separate ameloblasts

62
Q

What are enamel rods/enamel prism?

A

Formed by rod segments

Stacked on one another, very specific keyhole shape

63
Q

What is inter-rod substance?

A

Secreted by ameloblasts and found between enamel rods

64
Q

What is the rod sheath?

A

Organic material between rods and rod substance

65
Q

What percentage is enamel mineralized after the 2nd stage?

A

96% mineralized. Only 4% matrix left

66
Q

What is the source of calcium hydroxyapatite?

A

Mantle dentin and stratum intermedium

67
Q

When does termination of amelogenesis occur?

A

When reduced enamel epithelium forms

68
Q

What is reduced enamel epithelium?

A

Cellular sheath that forms on formed enamel

Consists of 4 layers

69
Q

What are the 4 layers of reduced enamel epithelium?

A

Post ameloblasts
Stratum intermedium
Remnants of stellate reticulum
Outer enamel epithelium

70
Q

How are post ameloblasts formed?

A

Ameloblasts change from tall columnar to low cuboidal

No longer produce enamel matrix

71
Q

What happens to stratum intermedium, remnants of stellate reticulum and outer enamel epithelium During termination of amelogenesis?

A

None histodifferentiate

Some remnants of stellate reticulum may be left over

Stratum intermedium and outer enamel epithelium remain in the same sheath

72
Q

What is another word for the primary enamel cuticle?

A

Nasmyth’s Membrane

73
Q

What is the primary enamel cuticle?

A

Protective covering located between reduced enamel epithelium and formed enamel

Wears away after the tooth erupts

74
Q

What forms after the primary enamel cuticle wears away?

A

Secondary enamel cuticle/pellicle

75
Q

What is the function of reduced enamel epithelium?

A

Protects the underlying enamel

Participates in the early formation of the dentogingival junction

76
Q

What happens to the reduced enamel epithelium once the teeth erupt?

A

Remnants may form epithelial cell rests

Some cells are resorbed, others stay and have potential to give rise to cysts later on

77
Q

During which stage does organization occur?

A

Bell stage

IEE elongate, organelles become polarized forming preameloblasts

78
Q

When does the formative process occur?

A

During apposition & amelogenesis

Ameloblasts form in response to mantle dentin formation and then forms aprismatic enamel

79
Q

When does maturation occur?

A

During amelogenesis and after termination

Completion of selective resorption & calcification processes

80
Q

When does the protective stage occur?

A

During termination

Formation of REE and primary enamel

81
Q

When does induction occur?

A

When dentinogenesis & amelogenesis reaches the cervical loop

82
Q

How does root formation begin?

A

With the formation of Hertwigs Epithelial Root Sheath (HERS)

83
Q

What is Hertwigs Epithelial Root Sheath?

A

Forms from cervical loop

Grows inferiorly and encompasses the dental papilla

84
Q

Formation of coronal and radicular mantle dentin is the same except for what?

A

In radicular dentin formation Korff’s fibers will be arranged parallel to the DCJ instead of the DEJ

Forms AFTER coronal dentin

85
Q

When does the apical foramen form? What is it?

A

When root formation is complete

Opening in root apex for nerves, blood vessels and lymphatic vessels

86
Q

In what direction does dentin form? What does the PDL allow for?

A

Forms in a coronal direction

PDL allows for tooth movement occlusally

87
Q

When is root formation complete for single root teeth?

A

2 to 3 years after eruption

88
Q

When does cementum formation occur?

A

When HERS breaks down

89
Q

What is the hyaline layer of hopewell-smith?

A

Covers mantle dentin

Produced by IEE

facilitates adhesion of cementum

90
Q

What happens when HERS breaks down?

A

After partial breakdown, cell rests of Malassez form

Potential to form cysts when trapped

91
Q

What do cementoblasts form?

A

Cementum matrix

92
Q

Describe the formation of cementum

A

First the matrix forms

Then the matrix calcifies with calcium hydroxyapatite derived from mantle dentin

121 Histology & Embryology (15 decks)

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