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BDS2 BAMS Oral Biology > Dental development > Flashcards

Dental development Flashcards

ILO 8.5b: have knowledge of the form and function of the teeth and associated structures, and the oral environment, in health and disease

1
Q

what primary embryonic layers do all body tissues develop from?

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 the other parts of the teeth and supporting structures, not including enamel, derived from?

A

ectomesenchyme

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4
Q

what kind of epithelium is present in the epithelial lining

A

stratified squamous

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5
Q

what is the ectomesenchyme?

A

part of the ‘neural crest’ that develops beside the primative nervous system (ectoderm)

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6
Q

what do teeth develop from?

A

tooth germs

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7
Q

what do tooth germs consist of?

A
  • enamel organ
  • dental papilla
  • dental follicle
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8
Q

what is the neural crest? what does it develop into?

A
  • a fourth cell type between ectoderm and the neural tube
  • also called the ectomesenchyme
  • neural crest tissue migrates into the developing face and jaw
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9
Q

why does the disease mandibulofacial dysostosis develop?

A

failure of the ectomesenchyme cells to migrate into the developing face and jaw

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10
Q

list the stages of tooth development in order

6

A
  • dental lamina
  • bud
  • cap
  • bell
  • erupting tooth
  • root formation
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11
Q

label each part of this embryo - how many weeks old is it?

A

5-6 weeks old

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12
Q

what is the primary epithelial band? when does it appear? what does it develop from?

A

appears as a thickening in epithelium of embyronic mouth (stomodaeum) at 6 weeks IUL from the ectoderm

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13
Q

Notice the primary epithelial band in both the mandibular and maxillary processes. What relationship do they have to each other?

A

Maxilla labial to mandible

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14
Q

what is the dental lamina? when does it develop? what does it develop from? what does it form?

A

continued proliferation of the primary epithelial band at 7 weeks IUL from the ectoderm
* develops into the enamel organ

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15
Q

what does the primary epithelial band differentiate into?

A
  1. vestibular lamina - inner part of band
  2. dental lamina - outer part of band
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16
Q

what is shown here?

A

dental lamina - horse-shoe structure with tooth germs developing

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17
Q

what does the vestibular lamina develop into?

A

breaks down to form the buccal sulcus via apoptosis and vestibule between the cheeks, lips and gingivae

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18
Q

what is the bud stage? when does it develop?

A

the dental lamina thickens thickens into a bud stage enamel organ at 8-10 weeks IUL

dental lamina (A)
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19
Q

what forms around the dental lamina / bud stage enamel organ?

A

endomesenchymal condensation - dental papilla

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20
Q

what is the dental papilla originated from?

A

ectomesenchyme

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21
Q

what stage is shown here?

A

late bud stage, early cap stage

22
Q

what is the cap stage? when does it develop? what does it consist of?

A

the enamel organ forms a cap over the dental papilla at 11 weeks IUL
* EEE - external enamel epithelium
* IEE - internal enamel epithelium
* EEE and IEE meet at the cervical loop

23
Q

what is formed from this part of the cap stage enamel organ?

24
Q

what stage is shown here?

A

late cap stage, early bell stage

25
what is the bell stage? when does it develop?
the enamel organ differentiates with **more cell layers** and the **tooth shape is being defined** at **14 weeks IUL** - looks like a bell shape
26
what are the different cell layers of the bell stage enamel organ?
* stratum intermedium * stellate reticulum * EEE - external enamel organ * IEE - internal enamel organ
27
what is the role of the stellate reticulum?
stores the **gycogen** and **nutrients** for the **ameloblasts** to develop and produce the enamel matrix
28
what is the role of the stratum intermedium?
forms **dental knots** which form the cusps of teeth (mamalons, cingulum, molar cusps)
29
what determines the shape and position of cusps in teeth?
ectomesenchyme
30
what is a permanent tooth germ? when do they develop? when does the first permanent molar germ develop?
an **extension** on the **lingual** side of the **dental lamina**, becoming the dental lamina for the **permanent successor** at **12 weeks IUL** and the first permanent molar germ develops at **16 weeks** as a backwards extension
31
what is the late bell stage? when does it develop?
the **crown shape is being well defined** and **apposition of enamel and dentine** begins at **18 weeks IUL**
32
where do odontoblasts differentiate from? what do they do?
odontoblasts differentiate from **dental papilla cells** adjacent to the **IEE** and secrete **unmineralised dentine matrix** (*predentine*)
33
where do ameloblasts differentiate from? what do they do?
ameloblasts differentiate from **IEE cells** after dentine formation has begun and secretes an **enamel protein matrix** which is **partially mineralised** then completely mineralised once framework is established (organic part removed)
34
what are the different stages of ameloblast differentiation? | 4
* differentiation * secretion * maturation * regression
35
what occurs in ameloblast differentiation?
* **dentine induces IEE cells to differentiate** into ameloblasts * cells **elongate** and become **columnar** * **nucleus migrates to the basal end** of the cell
36
what occurs in the secretory phase in ameloblast differentiation?
* ameloblasts become **secretory cells** * they **synthesise** and **secrete** enamel matrix **proteins** (amelogenins) * matrix is **partially mineralised** (30%)
37
what occurs in the maturation phase in ameloblast differentiation?
* **most** of the matrix proteins are **removed** * **mineral content** of enamel is **increased** * mature enamel is **95%** mineral
38
what occurs in the regression phase in ameloblast differentitation?
* ameloblasts **regress** to form a **protective layer** - reduced enamel epithelium * involved in **eruption** * formation of **epithelium attachment/junctional epithelilum**
39
how does the crown get its shape? how does the roots get their shape?
* **migration** of the cervical loop maps the crown shape * **apical growth** of the cervical loop defines the root shape
40
what is Hertwig's epithelial root sheath?
* **two cell layered** structure originating from the **enamel organ** * when **apical growth** of the cervical loops start to guide root formation - **size and shape** * induces **formation of root dentine**
41
what happens when the initial layer of root dentine is formed?
* Hertwig's epithelial root sheath (HERS) **breaks up** - no enamel in root * remains of HERS persist as '**debris of Malassez**'
42
what is the name of the first layer of dentine called?
mantle dentine
43
what are calcospherites?
globular dentine - stains darker
44
how is cementum formed? how are Sharpey fibres formed?
* once the dentine layer is layed down, **mesenchymal cells** from the **follicle** contact the **dentine** and **differentiate** into cementoblasts which lay down cementum * fibres from the developing PDL are embedded in the cementum
45
what can the debris of Malassez become?
odontogenic cysts
46
what is the dental follicle? what is it derived from? what does it produce?
* **connective tissue sac** surrounding the enamel organ * derived from the **ectomesentchyme** * produces **cementum, PDL and part of the alveolar bone**
47
what is the enamel organ? what is it derived from? what does it produce?
* **epithelial** structure developed from the dental lamina * derived from the **ectoderm** * produces **enamel**
48
what is the dental papilla? what is it derived from? what does it produce?
* **condensed ectomesenchyme cells** beneath the enamel organ * produces **dentine and pulp**
49
what is shown here?
**aquired enamel defect** - line present as all teeth were developing at the same time but defected maybe due to infection
50
what is shown here?
**gemination** - single tooth that has broken down into two
51
what is shown here?
**fusion** - two separate teeth that have fused together
52
what is shown here?
**concrescence** - separate teeth are joined together by cementum

BDS2 BAMS Oral Biology (12 decks)

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