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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
What happens to the dental papilla during the bell stage?
 outer cells form preodontoblasts that will give rise to Dentin Central cells will form the pulp
26
What happens to the dental follicle during the bell stage?
Forms a membrane around the entire tooth germ Follicle will become encapsulated by bone and become either the maxilla or mandible
27
What happens to Dental lamina during the bell stage?
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
28
What happens to the stellate reticulum during the apposition stage?
It collapses
29
Which dental tissue forms first?
Dentin. Once Dentin forms then enamel can form
30
How are odontoblasts formed?
Pre-odontoblast attach to the basement membrane
31
What do the odontoblast do during the apposition stage?
Lay down the first layer of Dentin matrix (formed by collagen) and begin dentinogenesis
32
What is the first layer of formed Dentin called
Mantle Dentin
33
When do Ameloblasts form? What do they compose And what is it called?
After the mantle Dentin forms Forms the first layer of enamel matrix and begins Amelogenesis This first layer is called aprismatic enamel
34
What is aprismatic enamel?
First layer of formed enamel Forms in response to dentin formation
35
What does the basement membrane get renamed as during the apposition stage?
Membrane performative Disintegrates after attachment of odontoblasts and Ameloblasts
36
What forms the dentinoenamel junction?
Mantle Dentin and aprismatic enamel
37
What happens to the dental papilla during the apposition stage?
Form the dental pulp and become innervated with sensory nerves
38
What happens to ameloblasts after enamel is formed?
The Ameloblasts die. This is why teeth cannot repair themselves
39
What is dentinogenesis?
Dentin formation
40
During what stage does dentinogenesis occur?
Apposition stage
41
Where is mantle Dentin found? What is it formed by?
Found in Coronal and radicular Dentin Formed by odontoblast and is the layer closest to the DEJ & DCJ
42
What are Korff’s fibers? What type of Dentin are they found in?
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
What is the Dentin matrix formed by?
Odontoblasts Collagen fibers formed around (peritubular dentin) and between (intertubular) the odontoblastic processes
44
Where is Circumpulpal Dentin found?
In Coronal and ridicular Dentin  no Korff’s fibers, forms all remaining Dentin and the bulk of the tooth
45
What is housed in Dentin tubules?
Odontoblast and processes in formed Dentin. Peritubular dentin forms the tubul. and intertubular Dentin forms between the Dentin tubules
46
How is calcium hydroxyapatite formed?
When calcium salts crystallize during the mineralization process
47
Where does calcium hydroxyapatite crystallization occur?
At matrix vessels when they rupture and release the calcium hydroxyapatite in the Dentin matrix
48
What aids in mineralization?
Odontoblast producing mineralizing proteins like phospholipids and Phosphophoryn
49
What percentage is Dentin mineralized?
65 to 70%
50
What is mantle Dentin?
First Dentin formed Closest to the DEJ & DCJ Mantle Dentin always next to Junction with Enamel
51
What is Circumpulpal Dentin?
All remaining Dentin right up to the pulp
52
What is peritubular Dentin?
Forms Dentin tubules, highly calcified
53
What causes Dentin sensitivity?
Dentin is perforated and has channels. When recession occurs this portion is exposed and sensitivity can occur
54
What is inter-tubular Dentin?
Forms between the tubules, a little less calcified
55
What is pre-Dentin?
Newest formed, non-mineralized Dentin matrix. Closest to the pulp Made from collagen
56
What is coronal Dentin?
Dentin of the crown, forms before ridicular Dentin and contains the DEJ
57
What is radicular Dentin?
Dentin of the root, last to form after coronal and contains the DCJ
58
What is amelogenesis?
Enamel formation
59
What is Tome’s process?
Very end of the ameloblast, creates a rod space
60
What is the enamel matrix?
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
What are rod segments? What are they created by?
Increments of formed enamel matrix Created by 4 separate ameloblasts
62
What are enamel rods/enamel prism?
Formed by rod segments Stacked on one another, very specific keyhole shape
63
What is inter-rod substance?
Secreted by ameloblasts and found between enamel rods
64
What is the rod sheath?
Organic material between rods and rod substance
65
What percentage is enamel mineralized after the 2nd stage?
96% mineralized. Only 4% matrix left
66
What is the source of calcium hydroxyapatite?
Mantle dentin and stratum intermedium
67
When does termination of amelogenesis occur?
When reduced enamel epithelium forms
68
What is reduced enamel epithelium?
Cellular sheath that forms on formed enamel Consists of 4 layers
69
What are the 4 layers of reduced enamel epithelium?
Post ameloblasts Stratum intermedium Remnants of stellate reticulum Outer enamel epithelium
70
How are post ameloblasts formed?
Ameloblasts change from tall columnar to low cuboidal No longer produce enamel matrix
71
What happens to stratum intermedium, remnants of stellate reticulum and outer enamel epithelium During termination of amelogenesis?
None histodifferentiate Some remnants of stellate reticulum may be left over Stratum intermedium and outer enamel epithelium remain in the same sheath
72
What is another word for the primary enamel cuticle?
Nasmyth’s Membrane
73
What is the primary enamel cuticle?
Protective covering located between reduced enamel epithelium and formed enamel Wears away after the tooth erupts
74
What forms after the primary enamel cuticle wears away?
Secondary enamel cuticle/pellicle
75
What is the function of reduced enamel epithelium?
Protects the underlying enamel Participates in the early formation of the dentogingival junction
76
What happens to the reduced enamel epithelium once the teeth erupt?
Remnants may form epithelial cell rests Some cells are resorbed, others stay and have potential to give rise to cysts later on
77
During which stage does organization occur?
Bell stage IEE elongate, organelles become polarized forming preameloblasts
78
When does the formative process occur?
During apposition & amelogenesis Ameloblasts form in response to mantle dentin formation and then forms aprismatic enamel
79
When does maturation occur?
During amelogenesis and after termination Completion of selective resorption & calcification processes
80
When does the protective stage occur?
During termination Formation of REE and primary enamel
81
When does induction occur?
When dentinogenesis & amelogenesis reaches the cervical loop
82
How does root formation begin?
With the formation of Hertwigs Epithelial Root Sheath (HERS)
83
What is Hertwigs Epithelial Root Sheath?
Forms from cervical loop Grows inferiorly and encompasses the dental papilla
84
Formation of coronal and radicular mantle dentin is the same except for what?
In radicular dentin formation Korff’s fibers will be arranged parallel to the DCJ instead of the DEJ Forms AFTER coronal dentin
85
When does the apical foramen form? What is it?
When root formation is complete Opening in root apex for nerves, blood vessels and lymphatic vessels
86
In what direction does dentin form? What does the PDL allow for?
Forms in a coronal direction PDL allows for tooth movement occlusally
87
When is root formation complete for single root teeth?
2 to 3 years after eruption
88
When does cementum formation occur?
When HERS breaks down
89
What is the hyaline layer of hopewell-smith?
Covers mantle dentin Produced by IEE facilitates adhesion of cementum
90
What happens when HERS breaks down?
After partial breakdown, cell rests of Malassez form Potential to form cysts when trapped
91
What do cementoblasts form?
Cementum matrix
92
Describe the formation of cementum
First the matrix forms Then the matrix calcifies with calcium hydroxyapatite derived from mantle dentin

121 Histology & Embryology (15 decks)

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