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BDS2 BAMS - Oral biology > Dental development > Flashcards

Dental development Flashcards

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1
Q

what is enamel derived from

A

ectoderm

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2
Q

apart from enamel, where are the other parts of the teeth derived from

A

ectomesenchyme

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3
Q

what is the ectomesenchyme

A

part of the ‘neural crest’ that develops beside the primitive nervous system

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4
Q

where do teeth develop from

A

tooth germs

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5
Q

What are the stages of tooth development

A
  1. initiation
  2. morphogenesis
  3. cytodifferentiation
  4. matrix secretion
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6
Q

what happens at the initiation stage of tooth development

A
  • occurs at dental lamina
  • a space develops (‘stomodaeum’) in between maxillary process and mandibular process
  • primary epithelial band develops 5-6 weeks IUL
  • PEB divides into 2 parts (vestibular lamina and dental lamina)
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7
Q

when does the primary epithelial band develop

A

5-6 weeks IUL

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8
Q

what does the vestibular lamina breakdown to form

A

buccal sulcus

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9
Q

what is formed from the dental lamina

A

enamel organ

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10
Q

What happens during morphogenesis

A

Bud stage

  • thickening of dental lamina forms enamel organ
  • reorganisation of cells around enamel organ forming the dental papilla
  • enamel organ = enamel
  • dental papilla = all other structures

Cap stage

  • 11wks IUL
  • bud organises into a cap
  • External enamel epithelium (EEE) and Internal enamel epithelium (IEE) form cap over dental papilla
  • EEE and IEE meet at the cervical loop
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11
Q

What happens during the cytodifferentiation stage

A

Bell stage

  • 14 wks IUL
  • 4 cell layers in enamel organ:
    1. IEE
    2. EEE
    3. stratum intermedium
    4. stellate reticulus

permanent tooth germ takes shape

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12
Q

What happens in the matrix secretion stage

A

Late bell stage

  • 18 wks IUL
  • crown shape defined
  • dentine formation established
  • enamel formation beginning
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13
Q

How does the formation of dentine and enamel begin

A
  • dental papilla cells adjacent to IEE differentiate into odontoblasts
  • they lay down dentine matrix which is later mineralised (predentine)
  • once dentine formation has begun, IEE cells differentiate into ameloblasts, which form enamel
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14
Q

what is unmineralised dentine called

A

predentine

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15
Q

what is mineralised dentine made of

A

hydroxyapatite

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16
Q

During dentinogenesis, some ectomesenchyme cells differentiate at an early stage and keep themselves dormant, why?

A

they will make tertiary dentine if the odontoblast cells die

17
Q

what happens as the cells differentiate into odontoblasts/ ameloblasts

A
  • polarisation of cells

- increase in organelles in cells

18
Q

how is the enamel matrix different from the dentine matrix

A

enamel doesn’t have collagen

19
Q

How is enamel formed

A
  1. Differentiation
    - Dentine induces IEE cells to differentiate into ameloblasts
  2. Secretory phase
    - ‘tongue’ process
    - ameloblasts synthesise and secrete the enamel matrix proteins
    - crystallites laid down in organised way to create structure of enamel rods (matrix mineralised to 30%)
  3. Maturation phase
    - removal of organic content of matrix to get 96% mineralisation
4. Protection phase
'regression stage'
- ameloblasts regress to form a protective layer
- ready for eruption
- formation of the epithelial attachment
20
Q

when is the root formed

A

after the crown is completed

21
Q

how is the root formed

A
  • EEE and IEE meet at cervical loop
  • root shape defined by apical growth of the cervical loop = “hertwig’s epithelial root sheath”
  • HERS induces formation of root dentine by growing downwards
  • HERS breaks up after initial layer of root dentine formed
  • remains of HERS persist as ‘debris of Malassez’
  • Mesenchymal cells from the follicle contact the dentine, and differentiate into cementoblasts. These form cementum
22
Q

What are the remains of hertwigs root sheath called when it breaks down

what can they develop into

A

debris of Malassez

odontic cyst

23
Q

what is hypodontia

A

less teeth than there should be and strange shape

24
Q

what are supernumeray ‘mesio-dens’

A

lateral conoid tooth in between central incisors

25
Q

what is gemination

A

2 laterals on top of each other, growing together

26
Q

what is fusion

A

2 central and lateral incisors growing together

27
Q

what is dentinogenesis imperfecta

A

dentine not formed properly

28
Q

What is the part of the tooth germ that gives rise to cementum, PDL and alv. bone

A

dental follicle

29
Q

What is the part of the tooth germ that gives rise to dentine and pulp

A

dental papilla

30
Q

What is the part of the tooth germ that gives rise to enamel

A

enamel organ

31
Q

what is the condition called when the ectomesenchymal cells fail to migrate

A

mandibulofacial dysostosis

32
Q

what causes amelogenesis imperfecta

A
  • autosomal recessibe hypoplastic hypomaturation amelogenesis imperfecta
  • MMP 20 gene
  • located on long arm of chromosome 11 at position 22.3
  • provides instructions for making enamelysin
  • enamelysin cleaves other proteins, such as amelogenin and ameloblastin, into smaller pieces (easier to remove)

BDS2 BAMS - Oral biology (9 decks)

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