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BDS2 BAMS Oral Biology > Dental Development > Flashcards

Dental Development Flashcards

1
Q

What are the 3 embryonic layers

A

 ectoderm
 mesoderm
 endoderm

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2
Q

What is tooth enamel derived from

A

ectoderm

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3
Q

What is all parts of the teeth and supporting structures (except enamel) derived from

A

ectomesenchymal cells

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4
Q

What are ectomesenchyme

A

Ectomesenchyme is part of the ‘neural crest’ that develops beside the primitive nervous system (ectoderm)

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5
Q

What does tooth develop from

A

tooth germ

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6
Q

What is the fourth cell type that forms between the ectoderm and neural tube

A

ectomesenchyme

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7
Q

What does neural crest tissue migration form

A

the jaw and face

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8
Q

What does failure of the migration of ectomesenchymal cells result in

A

will generate a number of pathological syndromes – deficiency in the formation

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9
Q

What is a condition that is due to failure of ectomesenchymal cells

A

mandibulofacial dysostosis.

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10
Q

What are the stages in tooth development

A 
	initiation 
	morphogenesis 
	cytodifferentiation 
	matrix secretion 
	root formation
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11
Q

What is present in tooth initiation

A

stomodaeum and maxillary & mandibular process

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12
Q

What is the stomodaeum

A

a space and it is this space that will form the mouth

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13
Q

When does the primary epithelium band form

A

approximately 6 weeks IUL

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14
Q

What does the primary epithelial band appear as

A

the thickening in the epithelium of the embryonic mouth (stomodaeum)

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15
Q

What will the primary epithelial band eventually form

A

dental lamina

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16
Q

When does the dental lamina appear

A

Appears approximately 7 weeks IUL

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17
Q

What is the 2 parts that the jaw is divided into

A

vestibular lamina

dental lamina

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18
Q

What is the vestibular lamina

A

will break down to form the buccal sulcus

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19
Q

What is the dental lamina

A

enamel organ develops from it

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20
Q

What is the shape of the dental lamina

A

horse shoe shaped

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21
Q

Where are the tooth germs formed

A

spaces in the DL

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22
Q

When does the bud stage occur

A

Occurs approximately 8-10 weeks IUL

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23
Q

What happens in the bud stage

A

The dental lamina thickens into a ‘bud’ stage enamel organ

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24
Q

What happens to the ectomesenchymal cells surrounding the dental lamina

A

he ectomesenchymal cells surrounding condensate and this is called the dental papilla

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25
Q

What holds the structure of the tooth - dental papilla or enamel organ

A

enamel organ

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26
Q

When does the cap stage occur

A

It occurs at approximately 11 weeks IUL

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27
Q

What happens in the cap stage

A

The enamel organ forms a cap on top of the dental papilla

Consists of 2 epithelium

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28
Q

What are the 2 epithelium in the cap stage

A

 external enamel epithelium

 internal enamel epithelium

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29
Q

Where do the EEE and IEE meet

A

These two meet at the cervical loop which is the reference for the formation of the root

30
Q

When does the bell stage occur

A

at approximately 14 weeks IUL

31
Q

What happens in the bell stage

A

There are more cell layers differentiated
The tooth shape is being defined
The bell stage enamel organ has 4 cell layers

32
Q

What are the 4 cell layers

A

 stratum intermedium
 internal enamel epithelium
 stellate reticulum
 external enamel epithelium

33
Q

What is found in the stellate reticulum that indicates it has a function to maintain the tissues

34
Q

Where does the crown pattern formation begin

A

The process in forming a tooth does not occur all the way through that structure – it starts at the nodes at the tip cusp area and works downwards.

35
Q

When does the dental lamina for the permanent successor appear

A

At approximately the 12th week, an extension appears on the lingual side of the dental lamina – this is the dental lamina for the permanent successor

36
Q

When do the 1st permanent molar germs appear

A

At about 16th week, the 1st permanent molar germ develops as a backwards extension of the dental lamina

37
Q

When does the late bell stage occur

A

Occurs at 18 weeks IUL

38
Q

What happens in the late bell stage

A

The crown shape is well defined (‘crown’ stage enamel organ)
The apposition of enamel and dentine begins

39
Q

How does dentine and enamel formation begin

A

The dental papilla cells adjacent to the IEE differentiate into odontoblasts
Odontoblasts lay down dentine matrix, which is later mineralized
Once dentine formation has begun, IEE cells differentiate into ameloblasts which form enamel

40
Q

When ectomesenchymal cells divide why are some ‘kept waiting’

A

It is triggered later for reparative tertiary dentine production.

41
Q

What are the two stages of enamel formation

A
  1. protein matrix is deposited but the matrix is only partially mineralized (30%)
  2. once this framework is established, the organic part is removed, and mineralisation is completed (‘maturation’)
42
Q

What happens to ameloblasts during amelogensis

A

 the ameloblasts change form and function several times during amelogenesis

43
Q

What are the several stages in the differentiation of ameloblasts

A 
	morphogenic 
	histodifferentiation 
	secretory (initial) 
	secretory (tomes process)
	maturative (ruffle-ended) 
	maturative (smooth) 
	protective
44
Q

When do the stages of ameloblast differentiation occur

A

The enamel is formed from the crown downwards

All the stages are happening at the same time in different areas

45
Q

What are the different phases of amelogenesis

A

Ameloblast differentiation
secretory phase
maturation phase
protection phase

46
Q

What happens in ameloblast differentiation

A

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

47
Q

What happens in the secretory phase

A

Ameloblasts become secretory cells
They synthesize and secrete the enamel matrix proteins (amelogenins)
The matrix is partially mineralized (30% mineral as seeded crystallites)
The proteins are organized in such a way that they allow supersaturation onto the crystallite

48
Q

What happens in the maturation phase

A

Most of the matrix proteins are removed
The mineral content of enamel is increased
Mature enamel is 95% mineral

49
Q

What happens in the protection phase

A

Ameloblasts regress to form a protective layer – the reduced enamel epithelium
It is involved in eruption
It is when the formation of the epithelium attachment occurs

50
Q

Why are newly erupted teeth more susceptible to acid attack

A

Although there is a mineral content change, the mineral carbonate apatite is present in the initial eruption and will be reduced during the lifetime. It is more susceptible to acid attack. We use sealants to protect the tooth and try and speed up the process of maturation

51
Q

What is amelogensis imperfecta due to

A

Due to autosomal recessive hypoplastic hypomaturation amelogenesis imperfecta

52
Q

What gene is associated with amelogensis imperfecta and where is it located

A

MMP 20 gene or MMP20

It is located on chromosome 11

53
Q

What does MMP20 do

A

It provides the instructions for making enamelysin which is what breaks down enamelin which is required to allow mineral to mature the enamel

54
Q

What does enamelysin do

A

Enamelysin cleaves other proteins, such as amelogenin and ameloblastin, into smaller pieces making it easier to remove

55
Q

What is the phenotype of amelogenesis imperfecta

A

It results in teeth that are more yellow than what is expected, rough and shiny. When you are eating the teeth are more frail. They are hard to restore due to lack of mineral to bond to.

56
Q

How does amelogenesis imperfecta appear in radiographs

A

The enamel cannot be seen in radiographs due to the reduced mineral content making it the same radiopacity as dentine

57
Q

What is dentinogenesis imperfecta

A

Enamel is formed but dentine didn’t doesn’t have the proper maturation making enamel flake due to the lack of support from dentine.

58
Q

How does the radiograph of dentinogenesis imperfecta appear

A

The radiograph of someone with this condition shows that there is no difference between pulp and dentine due to reduced density of dentine

59
Q

When does root formation occur

A

Root formation begins after crown formation

60
Q

What maps out the shape of the crown

A

The enamel organ maps out the shape of the crown

61
Q

What maps out root shape

A

apical migration of cervical loop

62
Q

What is the cervical loop called in root formation

A

Hertwig’s epithelial root sheath

63
Q

What does HERS do

A

This is a 2-cell-layered structure, in contrast to the 4-layered enamel organ
induces formation of root dentine

64
Q

What happens after the initial layer of root dentine is formed

A

HERS breaks up so that there is no enamel in the root

65
Q

What are remains of HERS called

A

debris of malassez which may develop into a cyst

66
Q

How are cementoblasts formed

A

Mesenchymal cells form the follicle contact the dentine and differentiate into cementoblasts
These form cementum
The fibres from the developing PDL are embedded in the cementum (Sharpey’s fibres)

67
Q

How can teeth developmental abnormalities happen

A

 prenatal
 postnatal
 inherited
 acquired

68
Q

What can teeth developmental abnormalities effect

A 
	number
	shape
	size 
	structure
	eruption
69
Q

What is gemination

A

This is when from one tooth, two are formed

70
Q

What is fusion

A

When the teeth join
Radiograph will show more than 1 root
Sometimes gemination is hard to differentiate form fusion

71
Q

What is concrescence

A

The coalescence or growing together of parts originally separate

BDS2 BAMS Oral Biology (10 decks)

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