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
Bell Stage: (3)
1.Under surface of the epithelium deepens and resemble a bell 2.Stratum intermedium formation 3.Crown attains full size and shape
26
Bell Stage (2)
1. Morphodifferentiation 2. Junction of IEE and OEE is called cervical loop (CL) – also the future site of the CEJ
27
Bell Stage | 1. Morphodifferentiation (2)
``` • Low Cuboidal shaped outer enamel epithelium (OEE) • Short columnar shaped inner enamel epithelium (IEE – will differentiate into ameloblasts) ```
28
Late Bell Stage | 2
 Dental lamina breaks and the separates the tooth from oral epithelium  Inner enamel epithelium (IEE) completes folding forming the future crown pattern
29
Late Bell Stage | Folding is due to
differential rates of mitotic | division in IEE
30
Late Bell Stage Under the influence of IEE mesenchymal cells differentiate into
odontoblasts that makes | dentin
31
Late Bell Stage | Subsequently IEE differentiate in to
ameloblasts and make enamel
32
Late Bell Stage | Site at which IEE differentiates determines
future cusp formation
33
Ameloblasts are derived from
inner enamel | epithelium
34
Ameloblasts are derived from inner enamel epithelium and the life cycle of ameloblasts has following stages: (7)
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
Secretory Stage Ameloblasts |  Intense (2) activity
synthetic and secretory
36
Secretory Stage Ameloblasts |  Forms (2)
enamel rod (R) and inter-rod (IR)
37
Secretory Stage Ameloblasts  Secrete --- on the newly formed mantle dentin.
granules
38
Secretory Stage Ameloblasts | Secretory products: (2)
 Proteins: |  Proteases
39
Proteins: (3)
 Amelogenin  Ameloblastin  Enamelin
40
Proteases (2)
 Enamelysin (MMP20) |  Kallikrein
41
Under the influence of epithelial cells | mesenchymal cells differentiate into
odontoblasts that make dentin
42
Mantle dentin –
First layer of dentin formed by the newly differentiated odontoblasts, hypomineralized, and only in the crown of the tooth (30-50um thick)
43
Primary dentin –
Formed during tooth development (4um/day)
44
Secondary dentin –
Dentin formed after tooth eruption | 0.4um/day
45
Tertiary dentin –
Dentin produced in response to injury to | protect the pulp
46
``` 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 ```
Hertwig’s epithelial root | sheath
47
Tooth Development: Root Formation (2)
```  Odontoblasts differentiation and dentin formation  Completion of root formation ```
48
--- mostly removed before cementum is laid down
Fragmentation of Hertwigs epithelial root sheath (HERS),
49
Tooth Development: Cementum | Formation
Differentiation of cementoblasts from HERS or dental follicle cells
50
Tooth Development: Cementum Formation Remnants of HERS are called
epithelial | rests of Malassez
51
``` Cementum types (2) ```
 Acellular |  Cellular