Tooth Development: Putting it all together Flashcards

1
Q

Timing of deciduous

dentition (2)

A

• Eruption and
exfoliation
• Sequence of eruption

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2
Q

Timing of permanent

dentition (5)

A
• When the crown
begins to calcify
• When the crown is
completely calcified
• Completion of root
development
• Eruption
• Sequence of eruption
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3
Q

First sign of tooth development is at

A

6-7 weeks

in utero

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4
Q

• Deciduous teeth begin to calcify at

A

13-20

weeks in utero

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5
Q

By —- all deciduous teeth

have begun to calcify

A

18-20 weeks in utero

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6
Q

• Deciduous teeth erupt at

A

6-30 months

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7
Q

• First part of tooth to calcify is the

A

crown

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8
Q

Stages of Tooth Development (3)

A

I. Crown Formation:
II. Root Formation
III. Supporting Structures

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9
Q

I. Crown Formation: (5)

A
  1. Initiation
  2. Bud Stage
  3. Cap Stage
  4. Bell Stage
  5. Enamel and dentin
    formation
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10
Q

Primary Epithelial Band (2)

A

 Horseshoe shaped
 Correspond to future
dental arches

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11
Q

Primary Epithelial Band

Gives rise to (2)

A

 Dental lamina

 Vestibular lamina

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12
Q

Shh Is Expressed In The — And
Pax9 In The — Where The Tooth
Bud Would Form

A

Epithelium

Mesenchyme

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13
Q

Initiation of Tooth

Development (3)

A
 Placode formation 
 Epithelial outgrowth into
the mesenchyme
 Initial odontogenic
potential lies in the
epithelium subsequently
shifts to mesenchyme
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14
Q

Placode formation –

A

Epithelial thickening.

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15
Q

Initial odontogenic
potential lies in the
epithelium subsequently
shifts to mesenchyme –

A
the neural crest
mesenchyme induces
the oral ectoderm to
become the dental
lamina
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16
Q

Bud Stage (5)

A
 Epithelial cells show no
major changes
 Shh, Lef-1 and Eda-Edar
involved in placode
formation (ectoderm
thickening)
 Mesenchyme beneath starts
to condense by the factors
secreted by the epithelium
 Cross-talk between the
epithelium and the
mesenchyme
 Odontogenic potential in the
epithelium
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17
Q

Cap Stage

A

Epithelium proliferates.
Mesenchyme continue to condense.
Looks like “Cap” sitting on a ball of
mesenchyme

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18
Q

Tooth germ: (2)

A

 Enamel organ – Enamel of the
tooth
 Dental papilla – Dentin (outer)
and pulp (inner)

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19
Q

Bud to cap stage transition is

regulated by

A

signaling molecules

and transcription factors

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20
Q

Dental follicle or Dental Sac –

A
Supporting structures (Cementum / Periodontium / alveolar bone
proper)
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21
Q

Enamel knot –

A

It is a key signaling center consist of cluster of non-dividing cells determines cusp
formation. Primary and secondary enamel knot

22
Q
Cap Stage Histodifferentiation
Cells in the enamel organ synthesize
--- in to the ECM.
Hydrophilic and pull water in to
enamel organ.
A

glycosaminoglycans

23
Q

Cap Stage Histodifferentiation
Increase in fluid volume force the
cells apart leading to formation of

A

star shaped stellate reticulum cells

24
Q

Enamel organ epithelial cells (2)

A

 Inner enamel epithelium

 Outer enamel epithelium

25
Q

Bell Stage: (3)

A

1.Under surface of the epithelium deepens and
resemble a bell
2.Stratum intermedium formation
3.Crown attains full size and shape

26
Q

Bell Stage (2)

A
  1. Morphodifferentiation
  2. Junction of IEE and OEE is called
    cervical loop (CL) – also the future
    site of the CEJ
27
Q

Bell Stage

1. Morphodifferentiation (2)

A
• Low Cuboidal shaped outer
enamel epithelium (OEE)
• Short columnar shaped inner
enamel epithelium (IEE – will
differentiate into ameloblasts)
28
Q

Late Bell Stage

2

A

 Dental lamina breaks and the separates the
tooth from oral epithelium
 Inner enamel epithelium (IEE) completes
folding forming the future crown pattern

29
Q

Late Bell Stage

Folding is due to

A

differential rates of mitotic

division in IEE

30
Q

Late Bell Stage

Under the influence of IEE mesenchymal cells
differentiate into

A

odontoblasts that makes

dentin

31
Q

Late Bell Stage

Subsequently IEE differentiate in to

A

ameloblasts and make enamel

32
Q

Late Bell Stage

Site at which IEE differentiates determines

A

future cusp formation

33
Q

Ameloblasts are derived from

A

inner enamel

epithelium

34
Q

Ameloblasts are derived from inner enamel
epithelium and the life cycle of ameloblasts
has following stages: (7)

A
  1. Morphogenetic stage
  2. Histodifferentiation stage
  3. Initial secretory stage (no Tome’s
    process)
  4. Secretory stage (Tome’s process)
  5. Ruffle ended ameloblast of the
    maturation stage
  6. Smooth ended ameloblast of the
    maturation stage
  7. Protective stage
35
Q

Secretory Stage Ameloblasts

 Intense (2) activity

A

synthetic and secretory

36
Q

Secretory Stage Ameloblasts

 Forms (2)

A

enamel rod (R) and inter-rod (IR)

37
Q

Secretory Stage Ameloblasts
 Secrete — on the newly formed
mantle dentin.

A

granules

38
Q

Secretory Stage Ameloblasts

Secretory products: (2)

A

 Proteins:

 Proteases

39
Q

Proteins: (3)

A

 Amelogenin
 Ameloblastin
 Enamelin

40
Q

Proteases (2)

A

 Enamelysin (MMP20)

 Kallikrein

41
Q

Under the influence of epithelial cells

mesenchymal cells differentiate into

A

odontoblasts that make dentin

42
Q

Mantle dentin –

A

First layer of dentin formed by the newly
differentiated odontoblasts, hypomineralized, and only in the
crown of the tooth (30-50um thick)

43
Q

Primary dentin –

A

Formed during tooth development (4um/day)

44
Q

Secondary dentin –

A

Dentin formed after tooth eruption

0.4um/day

45
Q

Tertiary dentin –

A

Dentin produced in response to injury to

protect the pulp

46
Q
Tooth Development: Root Formation
IEE and OEE form the
cervical loop proliferate
downward to form double
layered structure called
---, also the site of
the CEJ
A

Hertwig’s epithelial root

sheath

47
Q

Tooth Development: Root Formation (2)

A
 Odontoblasts
differentiation and dentin
formation
 Completion of root
formation
48
Q

— mostly removed
before cementum is
laid down

A

Fragmentation of
Hertwigs epithelial
root sheath (HERS),

49
Q

Tooth Development: Cementum

Formation

A

Differentiation of
cementoblasts from
HERS or dental
follicle cells

50
Q

Tooth Development: Cementum
Formation
Remnants of HERS
are called

A

epithelial

rests of Malassez

51
Q
Cementum
types (2)
A

 Acellular

 Cellular