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BDS2 BAMS > Dental development > Flashcards

Dental development Flashcards

1
Q

All body tissues develop from 3 primary embryonic layers. What are these?

A
  • Ectoderm
  • Mesoderm
  • Endoderm
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2
Q

Which primary embryonic layer does tooth enamel derive from?

A
  • Ectoderm
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3
Q

Tooth enamel is derived from ectoderm. Where are all other parts of the teeth and supporting structures derived from?

A
  • Ectomesenchyme
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4
Q

What is Ectomesenchyme?

A

Part of the neural crest that develops beside the primitive nervous system (ectoderm)

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5
Q

What do teeth develop from?

A

‘tooth germs’

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6
Q

A fourth cell type forms between the ectoderm and the neural tube. What is this called?

A

The ‘neural crest’

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7
Q

What is the neural crest tissue also called?

A

Ectomesenchyme

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8
Q

Do neural crest tissues migrate into the developing face and jaw?

A
  • Yes
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9
Q

Neural crest tissue migrates into the developing face and jaw which causes projections that will form the face. What occurs if there is failure of the migration of these cells?

A
  • This will cause a deficiency in the formation of the face
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10
Q

What is mandibulofacial dysostosis caused by?

A

Failure of ectomesenchymal cells to migrate

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11
Q

What are common signs of mandibulofacial dysostosis? (4 points)

A
  • Mandible is smaller
  • Eye sockets are fur ther apart
  • Ear position is lower than normal
  • Abscence of permanent teeth is possible
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12
Q

What is the first stage in tooth development?

A
  • Initiation

the dental lamina

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13
Q

What is the Stomodaeum?

A

The space that will form the mouth

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14
Q

When does the primary epithelial band develop?

A

At approx. 6 weeks IUL

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15
Q

What does the primary epithelial band appear as?

A
  • Appears as a thickening in epithelium of the embryonic mouth (stomodaeum)
  • Multiplication of oral epithelium cells projection of the epithelium onto Ectomesenchymeal surface
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16
Q

When does the dental lamina form?

A
  • Approx. 7 weeks IUL
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17
Q

The primary epithelial band will grown into the jaw and divide into 2 parts at approx. 7 weeks IUL. What are the 2 parts?

A
  • Vestibular lamina: which will break down to form the buccal sulcus
  • Dental lamina: from which the enamel organ develops
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18
Q

What is the shape of the structure of the dental lamina?

A

Horseshoe shape

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19
Q

What is the second stage of tooth development?

A
  • Morphogenesis

bud and cap stage

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20
Q

When does the ‘bud’ stage occur?

A

At approx. 8 weeks IUL

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21
Q

What is the process of the ‘bud’ stage? (2 points)

A
  • Dental lamina thickens into a ‘bud’ stage enamel organ

- An ectomesenchymal condensation appears and this is the dental papilla

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22
Q

What is the shape of a tooth determined by?

A
  • The enamel organ
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23
Q

When does the ‘cap’ stage occur?

A
  • Approx. 11 weeks IUL
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24
Q

Then enamel organ forms a ‘cap’ over the papilla. What does the ‘cap stage’ enamel organ include? (2 points)

A
  • External enamel epithelium

- Internal enamel epithelium

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25
Q

In the ‘cap’ stage where do the external enamel epithelium and the internal enamel epithelium meet?

A
  • At the cervical loop

- This is the reference point formation of the root (this is the cervical region of the tooth)

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26
Q

The enamel organ can be called a placode. What is this?

A

The enamel organ forming bud stage and forming tooth

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27
Q

What 3 organs other than teeth can placodes be seen?

A
  • Nail
  • Hair
  • Mammary glands
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28
Q

What are the oral implications of hypohidrotic ectodermal dysplasia? (3 points)

A
  • Not as many teeth as would expect
  • Shape of teeth being formed is different
  • Arrangement - some teeth are impacted
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29
Q

Apart from teeth, what else is affected by severe hypohidrotic ectodermal dysplasia? (3 points)

A
  • Hair
  • Nails
  • Mammary glands
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30
Q

What is the third stage of dental development?

A
  • Cytodifferentiation

bell stage

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31
Q

When is the ‘bell’ stage?

A

Approx. 14 weeks IUL

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32
Q

What happens in the bell stage of development? (2 points)

A
  • More cell layers differentiated

- Tooth shape is being defined

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33
Q

The ‘bell’ stage enamel organ has 4 cell layers. What are these?

A
  • Stratum intermedium
  • Stellate reticulum
  • Internal enamel epithelium
  • External enamel epithelium
34
Q

Are there nutrients present in the early bell stage?

A
  • Yes
35
Q

Explain the crown pattern formation of teeth?

A
  • Process of forming a tooth doesn’t occur all the way through the structure
  • Starts at the tooth cusp area
  • Differentiated cell start to produce dentine then enamel
  • This occurs from the cusps downwards
  • When look at changes in the formation of the tooth - it occurs in layers from the cusp downwards to the cervical region
36
Q

When approximately does an extension appear on the side of the dental lamina?

A

At approx. 12 weeks

37
Q

What is the dental lamina produced for?

A

For the permanent successor

38
Q

Approximately when doe the first permanent molar germ develop as a backwards extension of the dental lamina?

A

At approx. 16 weeks

39
Q

What is the fourth stage of dental development?

A
  • Matrix secretions
40
Q

When does then late ‘bell’ stage occur?

A

At approx. 18 weeks IUL

41
Q

What happens in the late ‘bell’ stage?

A
  • Crown shape is well defined
  • Apposition of enamel and dentine begins
  • (dentine formation is established and then enamel formation begins)
42
Q

How is dentine and enamel initially formed? (3 points)

A
  • Dental papilla cells adjacent to the IEE differentiate into odontoblasts
  • Odontoblasts lay down dentine matric, which is later mineralised
  • Once dentine formation has begun, IEE cells differentiate into ameloblasts, which form enamel
43
Q

What happens in the process of dentinogenesis? (4 points)

A
  • Odontoblast differentiation from IEE
  • Deposition of dentine matrix (mainly collagen)
  • This unmineralised dentine is predentine
  • Mineralisation of dentine (hydroxyapatite)
44
Q

Enamel is very highly mineralised. What is it as a %?

A

96% mineralised

45
Q

Enamel is made in 2 stages. What are these?

A
  1. Protein matrix deposited (matrix is partially mineralised - 30%)
  2. Once this framework is established, the organic part is removed and mineralisation is complete (maturation)
46
Q

During amelogenesis what happens to the ameloblasts?

A
  • They change form and function several times
47
Q

What are the 4 main stages of ameloblast differentiation?

A
  • Differentiation
  • Secretion
  • Maturation
  • Regression
48
Q

What are the 7 stages of ameloblast differentiation?

A
  1. Morphogenic
  2. Histodifferentiation
  3. Secretory (initial)
  4. Secretory (tomes process)
  5. Maturative (ruffle-end)
  6. Maturative (smooth)
  7. Protective
49
Q

What happens to ameloblasts during the first stage of ameloblast differentiation? (3 points)

A
  • Dentine induces IEE cells to differentiate into ameloblasts
  • They elongate, becoming columnar
  • The nucleus migrates to the basal end of the cell
50
Q

What happens during the secretory phase of amelogenesis? (3 points)

A
  • Ameloblasts become secretory cells
  • They synthesise and secrete the enamel matrix proteins (amelogenins)
  • The matrix is partially mineralised (30% mineral as seeded crystallites)
51
Q

What happens during the maturation phase of amelogenesis? (3 points)

A
  • Most of the matrix proteins are removed
  • Mineral content of enamel is increased
  • Mature enamel is 95% mineral
52
Q

What happens during the protection phase of amelogenesis? (3 points)

A
  • Ameloblasts regress to form a protective layer - the reduced enamel epithelium
  • Involved in eruption
  • Formation of epithelial attachment
53
Q

An example of amelogenesis imperfecta is autosomal recessive hypoplastic hypomaturation amelogenesis imperfecta. What gene causes this type of AI and what chromosome is it located on?

A
  • Matrix metallopeptidase 20 gene (MMP20)

- Located on the long (q) arm of chromosome 11 at position 22.3

54
Q

What does the matrix metallopeptidase 20 (MMP20) gene provide instruction for making?

A

Provides instruction for making enamelysin

55
Q

What does enamelysin do?

A

-It cleaves other proteins, such as amelogenin and ameloblastin, into smaller pieces (easier to remove)

56
Q

What is the enamel like in people with amelogenesis imperfecta? (7 points)

A
  • Yellow in colour
  • Less translucent
  • More opaque
  • Rough
  • Dull (not shiny)
  • Irregularities
  • Formation of tooth might not occur as it should so shape irregularities
57
Q

What might you see on an x-ray of someone with amelogenesis imperfecta?

A
  • Vertical bone loss

- Can’t see clear difference of where enamel is and where dentine is

58
Q

What is dentinogenesis imperfecta?

A
  • Enamel is properly formed but dentine doesn’t have the proper level of maturation
59
Q

What can you not see in an x-ray of a patient with dentinogenesis imperfecta?

A
  • Can’t see pulp chambers (can’t see root canal)
60
Q

It can be difficult to give RCT to a patient with dentinogenesis imperfecta. Why is this? (2 points)

A
  • Dentine is easy to manipulate but can be a problem on its own - if you deviate file to wrong direction it can cause a big mess
  • Radiographs will not show shape and length of root (makes it more difficult)
61
Q

What is the 5th stage in tooth development?

A
  • Root formation
62
Q

Does crown formation have to be complete for root formation to begin?

A

Yes

63
Q

What happens during root formation?

A
  • The enamel organ maps out the shape of the crown
  • The EEE and IEE meet at the cervical loop
  • Migration of the cervical loop maps the crown shape (migration downwards starts to create the root)
64
Q

What is the root shape defined by and what is the name for this?

A
  • Defined by the apical growth of the cervical loop

- This is called Hertwig’s epithelial root sheath

65
Q

How many layers of cells are found in the Hertwig’s epithelial root sheath and the enamel organ? (2 points)

A
  • HERS = 2 cell layer

- EO = 4 cell layer

66
Q

What is the process of root formation in relation to the Hertwig’s epithelial root sheath? (5 points)

A
  • HERS induces formation of root dentine
  • Once the initial layer of root dentine is formed, HERS breaks up (no enamel in root)
  • Remains of HERS persists as ‘debris of malassez’, which may develop into a cyst
  • Mesenchymal cells from the follicle contact the dentine, and differentiate into cementoblasts - these form cementum
  • Fibres from the developing PDL are embedded in the cementum (Sharpey’s fibres)
67
Q

What type of tissue is associated with the enamel organ ?

A

Epithelium

68
Q

What type of tissue is associated with the dental papilla ?

A

Ectomesenchyme

69
Q

What type of tissue is associated with the dental follicle?

A

Ectomesenchyme

70
Q

What is the origin of the enamel organ ?

A

Ectoderm

71
Q

What is the origin of the dental papilla ?

A

Neural crest

72
Q

What is the origin of the dental follicle ?

A

Neural crest

73
Q

What does the enamel organ produce ?

A

Enamel

74
Q

What does the dental papilla produce?

A

Dentine & pulp

75
Q

What does the dental follicle produce?

A

Cementum, PDL, alveolar bone (part)

76
Q

What are 4 different types of teeth developmental abnormalities?

A
  • Prenatal
  • Post natal
  • Inherited
  • Acquired
77
Q

What 5 things can teeth developmental abnormalities affect in relation to the tooth?

A
  • Number
  • Shape
  • Size
  • Structure
  • Eruption
78
Q

What does gemination mean?

A

From 1 tooth 2 have formed

79
Q

What is meant by the term fusion?

A

Where 2 teeth have fused together (usually see 2 roots o n a radiograph)

80
Q

What is meant by the term concrescence?

A

Connection is between cementum

BDS2 BAMS (57 decks)

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