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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
What holds the structure of the tooth - dental papilla or enamel organ
enamel organ
26
When does the cap stage occur
It occurs at approximately 11 weeks IUL
27
What happens in the cap stage
The enamel organ forms a cap on top of the dental papilla | Consists of 2 epithelium
28
What are the 2 epithelium in the cap stage
 external enamel epithelium |  internal enamel epithelium
29
Where do the EEE and IEE meet
These two meet at the cervical loop which is the reference for the formation of the root
30
When does the bell stage occur
at approximately 14 weeks IUL
31
What happens in the bell stage
There are more cell layers differentiated The tooth shape is being defined The bell stage enamel organ has 4 cell layers
32
What are the 4 cell layers
 stratum intermedium  internal enamel epithelium  stellate reticulum  external enamel epithelium
33
What is found in the stellate reticulum that indicates it has a function to maintain the tissues
glycogen
34
Where does the crown pattern formation begin
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
When does the dental lamina for the permanent successor appear
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
When do the 1st permanent molar germs appear
At about 16th week, the 1st permanent molar germ develops as a backwards extension of the dental lamina
37
When does the late bell stage occur
Occurs at 18 weeks IUL
38
What happens in the late bell stage
The crown shape is well defined (‘crown’ stage enamel organ) The apposition of enamel and dentine begins
39
How does dentine and enamel formation begin
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
When ectomesenchymal cells divide why are some 'kept waiting'
It is triggered later for reparative tertiary dentine production.
41
What are the two stages of enamel formation
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
What happens to ameloblasts during amelogensis
 the ameloblasts change form and function several times during amelogenesis
43
What are the several stages in the differentiation of ameloblasts
```  morphogenic  histodifferentiation  secretory (initial)  secretory (tomes process)  maturative (ruffle-ended)  maturative (smooth)  protective ```
44
When do the stages of ameloblast differentiation occur
The enamel is formed from the crown downwards | All the stages are happening at the same time in different areas
45
What are the different phases of amelogenesis
Ameloblast differentiation secretory phase maturation phase protection phase
46
What happens in ameloblast differentiation
Dentine induces IEE cells to differentiate into ameloblasts They elongate, becoming columnar The nucleus migrates to the basal end of the cell
47
What happens in the secretory phase
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
What happens in the maturation phase
Most of the matrix proteins are removed The mineral content of enamel is increased Mature enamel is 95% mineral
49
What happens in the protection phase
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
Why are newly erupted teeth more susceptible to acid attack
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
What is amelogensis imperfecta due to
Due to autosomal recessive hypoplastic hypomaturation amelogenesis imperfecta
52
What gene is associated with amelogensis imperfecta and where is it located
MMP 20 gene or MMP20 | It is located on chromosome 11
53
What does MMP20 do
It provides the instructions for making enamelysin which is what breaks down enamelin which is required to allow mineral to mature the enamel
54
What does enamelysin do
Enamelysin cleaves other proteins, such as amelogenin and ameloblastin, into smaller pieces making it easier to remove
55
What is the phenotype of amelogenesis imperfecta
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
How does amelogenesis imperfecta appear in radiographs
The enamel cannot be seen in radiographs due to the reduced mineral content making it the same radiopacity as dentine
57
What is dentinogenesis imperfecta
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
How does the radiograph of dentinogenesis imperfecta appear
The radiograph of someone with this condition shows that there is no difference between pulp and dentine due to reduced density of dentine
59
When does root formation occur
Root formation begins after crown formation
60
What maps out the shape of the crown
The enamel organ maps out the shape of the crown
61
What maps out root shape
apical migration of cervical loop
62
What is the cervical loop called in root formation
Hertwig’s epithelial root sheath
63
What does HERS do
This is a 2-cell-layered structure, in contrast to the 4-layered enamel organ induces formation of root dentine
64
What happens after the initial layer of root dentine is formed
HERS breaks up so that there is no enamel in the root
65
What are remains of HERS called
debris of malassez which may develop into a cyst
66
How are cementoblasts formed
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
How can teeth developmental abnormalities happen
 prenatal  postnatal  inherited  acquired
68
What can teeth developmental abnormalities effect
```  number  shape  size  structure  eruption ```
69
What is gemination
This is when from one tooth, two are formed
70
What is fusion
When the teeth join Radiograph will show more than 1 root Sometimes gemination is hard to differentiate form fusion
71
What is concrescence
The coalescence or growing together of parts originally separate

BDS2 BAMS Oral Biology (10 decks)

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