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BDS1 BAMS: Oral Morphology, Histology and Physiology > Tooth Development > Flashcards

Tooth Development Flashcards

1
Q

Which embryonic germ layer is enamel derived from?

A

Ectoderm

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2
Q

Which embryonic germ layer are dental and periodontal structures derived from? (but NOT enamel)

A

The ectomesenchyme

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3
Q

Which structure is the ectomesenchyme part of?

A

Neural crest

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4
Q

What do teeth develop from?

A

Tooth germs

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5
Q

Where does the neural crest form?

A

Between the ectoderm and the neural tube

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6
Q

Where does neural crest tissue migrate to?

A

Into the developing face and jaws

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7
Q

What is the primitive mouth called?

A

Stomodaeum

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8
Q

When does tooth development begin in embryonic development?

A

5-6 week old embryo

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9
Q

When does the primary epithelial band develop?

A

Approximately 6 weeks in utero

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10
Q

What is the primary epithelial band?

A

A thickening of the ectodermal epithelium of the embryonic mouth (stomadaeum)

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11
Q

Describe what happens to the primary epithelial band at 7 weeks in utero

A
  • The PEB grows into the jaw and divides into 2 parts: vestibular lamina and dental lamina
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12
Q

The primary epithelial band divides into the vestibular lamina and the dental lamina. What do each of these give rise to?

A
  • Vestibular lamina: forms the buccal sulcus

- Dental lamina: forms the enamel organ

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13
Q

What does the enamel organ develop from?

A

The dental lamina (which originates from the primary epithelial band - a thickening of the ectodermal epithelium of the mouth)

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14
Q

What shape is the dental lamina?

A

Horse-shoe shaped structure

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15
Q

What are the stages in tooth development?

A
  1. Bud stage
  2. Cap stage
  3. Bell stage
  4. Late bell stage
  5. Erupting tooth
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16
Q

Describe the ‘bud’ stage in tooth development

A
  • Occurs approx 8-10 weeks IUL
  • Dental lamina thickens into a bud stage enamel organ
  • An ectomesenchymal condensation appears and this is the dental papilla
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17
Q

Describe the ‘cap’ stage in tooth development

A
  • Approx 11 weeks IUL
  • The enamel organ forms a cap over the papilla
  • External enamel epithelium and internal enamel epithelium form. EEE and IEE meet at the cervical loop
18
Q

Describe the ‘bell’ stage in tooth development

A
  • Approx 14 weeks IUL
  • Tooth shape is being defined
  • Enamel organ has 4 cell layers: stratum intermedium, stellate reticulum, external enamel epithelium, internal enamel epithelium
19
Q

Describe tooth development at 12 weeks

A

An extension appears on the lingual side of the dental lamina
This is the dental lamina for the permanent successor

20
Q

At what stage does the 1st permanent molar germ develop and how does it do so?

A

At 16 weeks IUL, the 1st permanent molar germ develops as a backwards extension of the dental lamina

21
Q

Describe the ‘late bell stage’ of the enamel organ

A
  • Approx 18 weeks IUL
  • Crown shape is well defined
  • Apposition of enamel and dentine begin
22
Q

Describe the formation of dentine and enamel

A
  • Dental papilla cells adjacent to the IEE differentiate into odontoblasts
  • Odontoblasts lay down dentine matrix, which is later mineralised
  • Once dentine formation has begun, IEE cells differentiate into ameloblasts, which form enamel
23
Q

Describe the process of dentinogenesis

A
  • Odontoblast differentiation from dental papilla cells adjacent to IEE
  • Deposition of dentine matrix (mainly collagen)
  • The unmineralised dentine is termed predentine
  • Mineralisation of dentine (hydroxyapatite)
24
Q

Enamel is made in 2 stages. Describe these stages.

A
  1. Protein matrix deposited - matrix is partially mineralised
  2. Once this framework is established, the organic part is removed and mineralisation is completed (maturation)
25
Q

Ameloblasts change form and function several times during amelogenesis. Describe these stages

A
  1. Differentiation
  2. Secretion
  3. Maturation
  4. Regression
26
Q

Describe the ‘differentiation’ stage of amelogenesis

A
  • Dentine induces IEE cells to differentiate into ameloblasts
  • They elongate, becoming columnar
  • The nucleus migrates to the basal end of the cell
27
Q

Describe the ‘secretory’ stage of amelogenesis

A
  • Ameloblasts become secretory cells
  • The synthesise and secrete the enamel matrix proteins (amelogenins)
  • The matrix is then partially mineralised (30% mineral)
28
Q

Describe the ‘maturation’ stage of amelogenesis

A
  • Most of the matrix proteins are removed
  • Mineral content of enamel is increased
  • Mature enamel is 95% mineral
29
Q

Describe the ‘regression’ stage of amelogenesis

A
  • Ameloblasts regress to form a protective layer (the reduced enamel epithelium)
  • Involved in eruption
  • Formation of epithelial attachment
30
Q

When does root formation begin?

A

After crown formation is complete

31
Q

How is the root shape defined?

A

The root shape is defined by apical growth of the cervical loop, which is now called Hertwig’s epithelial root sheath (HERS)

32
Q

What is HERS?

A

Hertwig’s Epithelial Root Sheath

Formed by apical growth of the cervical loop

33
Q

Which structure induces formation of root dentine?

A

Hertwig’s Epithelial Root Sheath

34
Q

What happens to HERS once the initial layer of root dentine is formed?

A

HERS breaks up but persists as ‘debris of Malassez’ which may develop into a cyst

35
Q

Which cells give rise to cementoblasts?

A

Mesenchymal cells from the dental follicle contact the dentine and differentiate into cementoblasts

36
Q

What are the 3 parts of the tooth germ and what do they give rise to?

A
  1. Enamel organ: enamel
  2. Dental papilla: dentine, pulp
  3. Dental follicle: cementum, PDL, alveolar bone
37
Q

Where is the enamel organ derived from?

A

Ectoderm

38
Q

Where is the dental papilla derived from?

A

Neural crest

39
Q

Where is the dental follicle derived from?

A

Neural crest

40
Q

What type of tissue is the enamel organ?

A

Epithelium

41
Q

What type of tissue is the dental papilla?

A

Ectomesenchyme

42
Q

What type of tissue is the dental follicle?

A

Ectomesenchyme

BDS1 BAMS: Oral Morphology, Histology and Physiology (10 decks)

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