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Oral Biology > Tooth Development 1 > Flashcards

Tooth Development 1 Flashcards

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1
Q

What are the 3 developmental phases?

A

1) Initiation
2) Morphogenesis
3) Histogenesis

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2
Q

What occurs during Tooth development Initiation?

A
  • Locations of the teeth are established with the appearance of tooth germs
  • Tooth germs appear along the dental lamina (invagination of the oral mucosa)
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3
Q

What occurs during Tooth development Morphogenesis?

A
  • This stage determines the shape of the teeth

- Cell proliferation and movement determine the shapes of teeth

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4
Q

What occurs during Tooth development Histogenesis?

A
  • Differentiation of cells takes place to produce the fully formed dental tissues
  • Histogenesis begins during morphogenesis as all the phases are overlapping
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5
Q

What happens in the primitive oral cavity at the start of tooth development?

A
  • Mesenchymal condensation occurs underneath the dental epithelium
  • Has a Ectomesenchymal origin which came from the neural tube
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6
Q

What happens 6 weeks in utero?

A
  • Thickening of the oral epithelium

- Followed by invagination of the epithelium into the underlying mesenchyme to form the PRIMARY EPITHELIAL BAND

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7
Q

What happens 7 weeks in utero?

A
  • The PRIMARY EPITHELIAL BAND DIVIDES INTO:

+ Vestibular lamina (buccally)

+ Dental lamina (lingually)

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8
Q

7 weeks in utero: What does the Vestibular lamina contribute to?

A
  • Development of the vestibule
  • Delineates the lips and cheeks form the tooth bearing regions
  • The degeneration of the central epithelial cells produces the sulcus
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9
Q

7 weeks in utero: What does the Dental lamina contribute to?

A
  • Formation of the teeth
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10
Q

8 weeks in utero: What happens along the Dental lamina?

A
  • A swelling (tooth bud) develops on the deep surface of the Dental lamina
  • The Tooth buds are surrounded by a mesenchymal condensation
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11
Q

Tooth Germ Formation (odontogenesis): What are the different stages of development?

A
  1. Bud
  2. Cap
  3. Early Bell
  4. Late Bell
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12
Q

Odontogenesis: What happens during the Bud stage)

A
  • Enamel organ appears as a simple ovoid epithelial mass/Epithelial invagination
  • Surrounded by the Ectomesencymal condensation

Enamel organ and the Ecotomesencymal condensation are separated by a basement membrane

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13
Q

Odontogenesis: What happens during the Cap stage (11 weeks in utero)?

A
  • Invagination progression

- Peripheral cells start to arrange and differentiate into EXTERNAL and INTERNAL ENAMEL EPITHELIUM

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14
Q

Odontogenesis: What happens during the Cap stage (12 weeks in utero)?

A
  • Central cells within the enamel organ become separated = STELLATE RETICULUM
  • EXTERNAL ENAMEL EPITHELIUM becomes CUBOIDAL
  • INTERNAL ENAMEL EPITHELIUM becomes COLUMNAR
  • Surrounding Ectomesencymal cells proliferation into the :
    + Dental Papilla
    + Dental Follicle
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15
Q

Odontogenesis: What happens during the Early Bell stage (14 weeks in utero)?

A
  • INTERNAL ENAMEL EPITHELIUM alters shape and this determines crown shape
  • The Dental lamina breaks down
  • Dental Follicle undergoes differentiation:
    + Inner vascular fibrocellular condensation
    + Loose CT layer
    + Outer vascular layer lining the alveolus
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16
Q

Odontogenesis: What happens during the Early Bud stage (14 weeks in utero)?

A

4 distinct layers of enamel organ are present:

  1. External Enamel epithelium
  2. Stellate reticulum
  3. Stratum intermedium
  4. Internal Enamel epithelium
17
Q

What’s the External Enamel Epithelium?

A
  • Outer enamel epithelium which forms the outer later of cells in the enamel organ
  • Cuboidal in shape
  • Separated from the Dental Follice via a basement membrane
  • Possess large central nuclei and relatively little amounts of organelles for protein synthesis
18
Q

What’s the Cervical Loop?

A
  • The growing margin of the enamel organ

- Lies at the junction between the inner and outer enamel epithelium

19
Q

What’s the Stellate Reticulum?

A
  • Fills the space between the Inner and Outer dental epithelium
  • Star shaped cells with branching processes
  • Extracellular material secretion - Alkaline Phosphatase (important)
  • Protects the underlying tissues and maintains the tooth shape

Effect on crown outline

20
Q

What’s the Stratum Intermedium?

A
  • 2-3 layers of flat cells
  • Lies over the Internal Enamel Epithelium
  • Resembles stellate cells but with smaller spaces
21
Q

What’s the Internal Enamel Epithelium?

A
  • Columnar cells
  • Rich in RNA but contain no Alkaline Phsphatase
  • Separated from the dental papilla by a basement membrane and a cell free zone
22
Q

What happens during the Late Bell Stage?

A
  • Lingual downgrowths of the external enamel epithelium give rise to the permanent anterior teeth buds (5 months utero)
  • Dental lamina grows posteriorly to give rise to the tooth buds of the permanent posterior teeth (4 months utero)
23
Q

What happens during the Late Bell stage (2)?

A
  • Also known as the Appositional stage: formation of the dental hard tissues
  • Dentine always precedes enamel!!!
  • Hard tissue formation starts at the cusp tips
24
Q

What do the Internal enamel epithelial cells differentiate into?

A
  • Pre-ameloblasts
  • Pre-ameloblasts induce adjacent mesenchymal cells to differentiate into Odontoblasts
  • Odontoblasts produce pre-dentine and dentine
  • Dentine induces Ameloblasts to form enamel
25
Q

What are the Transitory structures in Odontogenesis?

A
  1. Enamel Knot
  2. Enamel Cord
  3. Enamel Niche
26
Q

What’s an Enamel Knot?

A
  • Localised mass of cells in the centre of the internal enamel epithelium
  • Non proliferative cells
  • Outline of the future fissures
  • Signalling centre*
  • Potentially an inducer of odontoblast differentiation
27
Q

What’s the Enamel Cord?

A
  • Strands of cells extending from the Stratum Intermedium into the Stellate Reticulum

Enamel Septum:
+ Enamel cord that completely splits the stellate reticulum

Enamel Navel:
+ The invagination where the enamel cord meets the external enamel epithelium

  • Focus for Stellate cell formation

Oral Biology (33 decks)

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