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Tooth development Flashcards

1
Q

When does primary dentition begin

A

6-8 weeks of gestation

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2
Q

When secondary dentition begin

A

20 week of gestation to 10 months after birth

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3
Q

When do permanent molars begin at

A

20th week of gestation to 5th year after birth (3rd molars)

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4
Q

What does the epithelial lining do?

A

It has odontogenic potential and initiates tooth development

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5
Q

What does the ectomesenchyme component do?

A

contains subsequent tooth development

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6
Q

What two components continuously interacts with each other during tooth development

A

Ectomesenchyme and ectoderm

If the sequence is interrupted, the process of tooth development is interrupted

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7
Q

What do neural plate cells do?

A

Forms a neural grove that deepens and folds until it pinches off to form the neural tube

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8
Q

What do lateral neural plate cells do?

A

Pinch off and form the neural crest cells that migrate throughout the body including the face region where it gives rise to the specialized CT of the face: ectomesenchyme

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9
Q

Stages of tooth development

A

Induction Phase
Bud Stage
Cap Stage
Bell Stage
Crown Stage
Root Stage

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10
Q

Dental lamina formation

A

An increased number of cell divisions in the thickened oral epithelium causes it to proliferate into the underlying mesenchyme. As a result of different rates of growth in the various parts of the proliferating epithelium, the ingrowth becomes locally thickened into buds, nearly spheridcal balls of epithelial cells. Each epithelial sphere is associated with a sphere of condensed mesenchyme.

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11
Q

Induction stage

A

Magical signaling at the enamel knot happens in the ectomesenchymal cells by the dental lamina that induce the ectodermal cells to start proliferating in specific and well spaced locations forming tooth placodes. This is still not well understood.

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12
Q

Where does the dental lamina develop?

A

Dental Lamina development starts anteriorly at the midline and proceeds posteriorly

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13
Q

Bud stage

A

Signaling from the neural crest cells (ectomesenchyme) induces the epithelial cells to proliferate and start budding into the region where the neural crest cells are.

Thickening in-growth of the oral epithelium that gives rise to the teeth buds (enamel organs)

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14
Q

Cap stage

A

Lots of proliferation at the lateral sides of the bud, causing the cells in the middle to invaginate.

Inner enamel epithelial and outer enamel epithelial cells.

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15
Q

What is the histodifferentiation of the cap stage

A

Inner enamel epithelium–> columnar
Outer enamel epithelium cuboidal

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16
Q

What is the dental papilla

A

Neural crest cells/ectomesenchyme encompassed by the enamel organ coalesce

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17
Q

What forms the dental follicle (dental sac)

A

Outer neural crest cells/ ectomesenchyme proliferate

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18
Q

what is the tooth germ made out of

A

OEE + IEE + dental papilla + dental follicle

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19
Q

What are the steps in development of the enamel organ

A

Thickening of IEE
Distinction of IEE and OEE
Development of dental papilla
Development of dental follicle/sac
Basement membrane

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20
Q

Where is the basement membrane located?

A

Between the IEE and the dental papilla

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21
Q

What happens during the bell stage

A

Cytodifferentiation occurs- cell size and function established
Morphodifferentiation- size and shape of crown established
Dental lamina disintegrates; extends caudally
Successional lamina forms
Enamel organ matures
Molar development

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22
Q

What is stellate reticulum

A

The cells inside the body of the enamel organ secrete water-absorbing glycosaminoglycans but hold onto each other through desmosomes so they look like stars.

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23
Q

What gives rise to the periodontium

A

Dental sac

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24
Q

What are pre-odontoblasts?

A

formed from the dental papilla cells adjacent to the IEE; induced by IEE. (in turn pre-odontoblasts induce IEE cells to become pre-ameloblasts.

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25
What is stratum intermedium
 flat cells line up adjacent to the inner enamel epithelium (required to induce ameleoblast development from IEE)
26
What components are involved in the bell stage during cytodifferentiation
Stellate reticulum Inner Enamel Epithelium (columnar) Outer Enamel Epithelium (cuboidal) Dental papilla Dental follicle
27
What are pre-odontoblasts
They are formed from the dental papilla cells adjacent to the IEE; induced by IEE
28
What happens to the stellate reticulum during the early cytodifferentiation process in the bell stage
cells inside the enamel organ that secrete glycosaminoglycans that pull water into the enamel organ allowing the tooth space for morphogenesis
29
What is present during early cytodifferentiation of the bell stage
stellate reticulum stratum intermedium inner enamel epithelium basement membrane dental papilla
30
What is happening during morphogenesis of the bell stage
secondary enamel knots signal to form the sites of the future cusps of the teeth this happens embryologically
31
True/False: Each tooth has a determined the cusp form prior to any tissue mineralization
True Fun fact: The formation of tooth cusp morphology is also polygenic and is being used by anthropologists to explore the origins of native Americans.
32
What is the successional lamina process of the bell stage?:
Outgrowth of the dental lamina on lingual side. Gives rise to primordium of enamel organ for tooth germ of permanent teeth
33
True/False: Only the anterior 10 teeth have primary teeth
True
34
True/False: The posterior molars have primary teeth and develop directly from the dental lamina.
False: the posterior molars don’t have primary teeth and develop directly from the dental lamina
35
What is the progression of the tooth development
In the region of the developing 1st permanent molar, the dental lamina becomes detached from the oral epithelium and progresses posteriorly as an epithelial cord
36
True/False: The successional teeth (permanent teeth) are developing their crowns at about the same time as the primary teeth (during early embryonic development)
True
37
True/False: The roots of the primary and successional teeth, however, develop at about the same time.
False: The roots of the primary and successional teeth develop at very different times.
38
What happens during the disintegration of the dental lamina during the bell stage
Remnants of dental lamina can form epithelial pearls since the cells needed to form enamel would be present where they shouldn’t be.
39
Do molars have deciduous precursors?
Nahhhh
40
True/False: Posterior-most extent of the dental lamina does not disintegrate but elongates posteriorly and gives rise to the permanent molars
True
41
What are the stages of tooth development
Induction phase Bud stage cap stage Bell stage Crown Stage Root Stage
42
What is overview of the bud phase
Dental lamina ectoderm grow into neural crest/ectomesenchyme
42
What is overview of the cap phase
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
42
What is overview of the induction phase
Formation of dental lamina and determination of future tooth location
43
What is overview of the bell phase
cytodifferentiation, morphodifferentiation, Formation of the successional lamina, disintegration of the dental lamin
44
What is overview of the crown phase
When hard tissue is laid down
45
What is overview of the root phase
Formation of the root
46
What happens when the dental papilla elongates
providies nutrition to ectomesenchymal cells and IEE
47
What happens during the late bell stage
Maturation begins at future cusp: ectomesenchymal cells of dental papilla line up to face the IEE and become pre-odontoblasts which stimulate the IEE cells to form pre-ameloblasts. The pre-amelobalst stimulates the maturation of the odontoblasts the secrete dentin. The production of dentin stimulates the maturation of the ameloblasts which secrete enamel.
48
How is ameloblasts and odontoblasts formed
Through lots of interactions between the inner enamel epithelium and dental papilla
49
What happens at future cusp
ectomesenchymal cells of dental papilla line up to face the IEE and become pre-odontoblasts
50
What does preodontoblasts do
Cause IEE cells to differentiate into preameloblasts
51
What is the final form of late bell stage cytodifferentiation
odontoblast
52
what does the production of dentin do?
stimulates the maturation of the ameloblasts which secrete enamel
53
What do pre-ameloblasts do
stimulates the maturation of the odontoblasts
54
What happens during the crown stage
In turn pre-odontoblasts induce IEE cells to become pre-ameloblasts. The appearance of pre-ameloblasts induce the pre-odontoblasts to become full odontoblasts that start laying down dentin(final form!) The dentin induces the pre-ameloblasts to become ameloblasts (final form!) and start laying down enamel (only when the stratum intermedium is there for support
55
What happens when the outern enamel epithelium gets closer to the IEE
it allows the ameloblasts to access blood supply & blood vessels start forming in the dental papilla
56
When does maturation begin
at the future cusp
57
How does maturation happen at the future cusp
ectomesenchymal cells of dental papilla line up to face the IEE and become pre-odontoblasts which stimulate the IEE cells to form preameloblasts
58
Where does the dental enamel junction form
It forms from where the basement membrane has been between the ectoderm and the ectomesenchyme from the beginning of tooth development
59
What occurs in the early crown stage
dentin is laid down first followed by enamel. The basement membrane separating the enamel organ from the dental papilla becomes the DEJ
60
What are the components of the reduced enamel epithelium
Outer Enamel epithelium Stellate reticulum Stratum intermedium Inner enamel epithelium/ Ameloblasts
61
What is reduced enamel epithelium
formed by collapse of outer enamel epithelium and stellate reticulum onto stratum intermedium and inner enamel epithelium/ameloblasts.
62
Where does the reduced enamel epithelium began at (REE)
Begins at the cusp
63
How does the REE get nutrients
Blood vessels in folds outside of the outer enamel epithelium provide nutrients to enamel organ
64
what does thick basal lamina do
Separates the pre ameloblasts from the pre odontoblasts
65
What triggers adjacent cells of the dental papilla to elongate
pre ameloblasts
66
What happens after the OEE is thrown into folds during the late bell stage
BVs invade these folds, derived from the dental follicle. The stellate reticulum collapses which brings the bvs and the OEE closer to the S. intermedium. Nutrients from the bvs now are transported by the OEE cells to the St. Intermedium w transports it to the preameloblasts. The preameloblasts trigger the adjacent cells of the dental papilla to elongate.
67
How does the enamel organ receive blood before hard tissue is laid down
the enamel organ receives its blood supply via blood vessels in the dental papilla.
68
What happens to the papilla blood vessels once the hard tissue is laid down
The papilla blood vessels can no longer supply the ameloblasts
69
How are the ameloblasts nourished after the hard tissue is laid down
The ameloblasts are then nourished via blood vessels from the outside of the outer enamel epithelium after the layers of the enamel organ collapse to form the reduced enamel epithelium (REE)
70
What does the REE give rise to
The Reduced Enamel Epithelium will give rise to the attachment epithelium that binds the gingiva to the hard tissue of the tooth
71
What is the cervical loop in the bell stage
Reflection of outer enamel epithelium onto inner enamel epithelium Lacks stratum intermedium Will elongate inferiorly during root development
72
True/false: The stratum intermedium is present at the cervical loop
False: No stratum intermedium at the cervical loop so cytodifferentiation ends up differently (no pre-ameloblasts develop)
73
What happens during the root formation stage
The crown stage ends when enamel and dentin formation reaches the cervical loop.
74
When does the crown stage end
ends when enamel and dentin formation reaches the cervical loop (point of the Cemento-Enamel Junction)
75
What happens if the stratum intermedium cells are not present during root formation
Without the Stratum Intermedium cells the Inner Enamel Epithelium can’t differentiate into a pre-ameloblast.
76
How is cementum produced
Echtomesenchymal cells from the dental sac reach the dentinal surface and are stimulated to become cementoblasts which secrete cementum
77
How is the alveolar bone produced
Echtomesenchymal cells from the dental sac that are farthest away from the dentinal surface differentiate into osteoblasts, making the alveolar bone.
78
What is hertwig's epithelial root sheath important for
Root shape Development of root dentin Development of root cementum
79
Does hertwig's epithelial root sheath form into the root
no
80
What is the epithelial diaphragm
Invaginations of the Hertwig’s Epithelial Root Sheath at the apex of the root
81
What determines the number of toots/tooths
epithelial diaphragm
82
What is single root development
epithelial root sheath grows apically as an epithelial cylinder from the cervical edge of the enamel organ.
83
How are multiple roots formed
occur when there are additional extensions of the diaphragm that meet in the midline separating the apical foramen into two or more foramen and subsequently, roots.
84
True/false: Root formation and tooth eruption occur simultaneously
True
85
True/false: the location of the base of the tooth does not change
true
86
Congenital tooth abnormalities
splitting of the tooth germ or fusion of adjacent tooth germs
87
What are the effects of trauma and infection regarding tooth development
can affect the development of permanent teeth and result in malformations in teeth such as: variations in size, shape, number, or structure

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