Tooth development Flashcards

1
Q

What are the 8 stages of tooth development in early intra-uterine life?

A

1) Primary epithelial band
2) Dental lamina formation
3) Bud stage
4) Cap stage
5) Early bell stage
6) Late bell stage
7) Root sheath and root formation
8) Root formation and formation of periodontal ligament and alveolar bone

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2
Q

At the beginning of week 6 what is the primitive mouth lined by?

A

Ectoderm

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3
Q

How does the primary epithelial band form?

A

Thickening of the embryo’s oral epithelium which lies above mesenchyme

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4
Q

What are the two primary epithelial bands shaped like?

A

Horse shoe

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5
Q

What is ectomesenchyme derived from?

A

Neural crest cells that have migrated to the region from neuroectoderm of the embryo

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6
Q

What is the primitive oral cavity called?

A

Stomodeum

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7
Q

How is the dental lamina formed?

A

Further thickening and growth of the arch shaped epithelial band into the underlying ectomesenchyme.

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8
Q

Where does the dental lamina begin to form?

A

Initially in the midline then progresses posteriorly

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9
Q

What are the two processes that the primary epithelial band divides into?

A

1) Buccal placed vestibular lamina - lips, buccal sulcus, cheeks
2) Lingual placed vestibular lamina - development of the teeth is ARCH shaped

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10
Q

What is initiation?

A

The development of individual tooth sites along the dental lamina with 10 deciduous tooth germs developing sequentially along each arch

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11
Q

What is morphogenesis?

A

The process that gives rise to the individual tooth shape under the influence of genetic programming and cell signalling from interactions between the epithelial and mesenchymal cells

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12
Q

What is histogenesis?

A

Differentiation of different cell types (ameloblast/odontoblast) to give rise to either mineralised tissue - enamel, dentine or cementum or non-mineralised such as pulp and periodontal tissues

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13
Q

What do oral epithelium signal to underlying mesenchyme via?

A

Bone morphogenic factors and fibroblast growth factors - these regulate gene expression

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14
Q

What do bone morphogenic factors induce?

A

The expression of mesenchymal homeobox gene transcription factors Msx 1 and Msx2 - Msx1 is found in the bud stage epithelium and Msx2 possibly a regulator in morphogenesis

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15
Q

Where do bioactive signalling molecules pass between?

A

Epithelium and mesenchyme, where they bind to cell receptors and set of a series of intracellular cascades that regulate gene expression thereby altering cell behaviour

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16
Q

In the superficial layer of the adult oral mucosa what are cells like?

A

Large and flattened

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17
Q

In the intermediate layer of the adult oral mucosa what are cells like?

A

Start to enlarge and become flattened in shape

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18
Q

In the basal layer of the adult oral mucosa what are cells like?

A

Cells are tall columnar, actively reproducing and cells move over the superficial layer over time

19
Q

What cell layers make up the embryonic oral epithelium/?

A

Superficial and basal

20
Q

What creates the primary epithelial band?

A

Multiplication of basal and superficial cells to increase tissue thickness and complex cell signalling and gene expression

21
Q

What characterises the early bud stage?

A
  • Spherical condensation of epithelial condensation surrounded by mesenchyme
  • No morphodifferentiation visible
  • No histodifferentiation visible
  • Ectodermal tissue origin
22
Q

What does the oval mass in the early bud stage penetrate into?

A

Surrounding ectomesenchyme which surrounds the enamel organ and is growing and condensing

23
Q

What characterises the cap stage?

A

Enamel organ looks like a cap
Morphodifferentiation is still not visible
- Early histodifferentiation is visible with recognisable:
Stellate reticulum
Outer enamel epithelium
Inner enamel epithelium

24
Q

What is the stellate reticulum?

A

Star shaped cells derived from the superficial cell layer

25
Q

What are the basal cell layers continuous with in the cap stage?

A

Outer and inner enamel epithelium

26
Q

What will the inner enamel epithelium become?

A

Ameloblast cell layer that lays down the tooth enamel

27
Q

What role does the stellate reticulum have?

A

Cushioning and nutrient role for the inner and outer enamel epithelium, supports production of enamel matrix

28
Q

What shape is the external enamel epithelium in the late cap stage?

A

Cuboidal

29
Q

What shape is the inner enamel epithelium in the late cap stage?

A

More columnar

30
Q

What is the dental follicle?

A

Mesenchymal cells proliferating and surrounding enamel organ

31
Q

What is the dental papilla?

A

Mesenchymal cells located beneath inner enamel epithelium and condensed into a mass within the concavity of the cap of the enamel organ

32
Q

What are the three embryological features we can see by the late cap stage?

A

Dental papilla, dental follicle and enamel organ

33
Q

What is the enamel organ derived from?

A

Ectoderm

34
Q

What is the dental papilla derived from?

A

Ectomesenchyme, derived from NCC’s, producing future dentine and pulp

35
Q

What is the dental follicle derived from?

A

Ectomesenchyme, produces the periodontium, cementum, periodontal ligament, alveolar bone

36
Q

What is the basement membrane?

A

It is between the enamel organ and dental papilla and is the site of the future ADJ

37
Q

What is the early bell stage characterised by?

A

Morphodifferentiation visible
Histodifferentiation visible (IEE cells become tall columnar)
Development of successional lamina from which permanent incisor, canine and premolar teeth develop after their deciduous tooth predecessor
Permanent molar teeth develop directly from the dental lamina as there is no deciduous teeth to be replaced

38
Q

What are the histologic features of stratum intermedium?

A

More inner compressed layer of flat cells

39
Q

What are the dental papilla and dental follicle characterised by in the bell stage?

A

Morphodifferentiation is very visible
Both composed of mesodermal/mesenchymal cells
Dental papilla differentiates into odontoblast layer and produces dentine
Dental follicle composed of flattened

40
Q

What is the late bell stage characterised by?

A

Morphodifferentiation of crown is complete
Ameloblast differentiation from IEE causes ectomesenchymal peripheral cells of the dental papilla to differentiate into tall columnar odontoblast cells
Enamel and dentine formation starts at the tips of future cusps/incisal edges occurring incrementally
Alveolar bone is deposited around the developing tooth

41
Q

What are the two main groups of proteins in enamel?

A

Amelogenins and non-amelogenins

42
Q

What is root formation characterised by?

A
Root sheath
Dental papilla
Dental follicle
Odontoblast layer
Epithelial rests of malassez
Cementoblasts
Developing alveolar bone
Developing cementum, periodontal ligament and root dentine
43
Q

What interactions are there in root formation?

A

Epithelial root sheath, dental follicle and dental papilla