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BDS2 BAMS > Dental Development > Flashcards

Dental Development Flashcards

1
Q

3 primary embryonic layers

A

ectoderm

mesoderm

endoderm

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2
Q

what embryonic tissue is enamel derived from?

A

ectoderm

all other tooth structures and supporting structures are derived from the ectomesenchyme

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3
Q

what structure do teeth develop from

A

tooth germs

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4
Q

what is the ectomesechyme part of?

A

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

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5
Q

what is the neural crest

A

A fourth cell type forms between the ectoderm and the neural tube (folds onto the neural grove)
- ectomesenchyme

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6
Q

what does the neural crest tissue migrate into

A

Neural crest tissue migrates into the developing face and jaws

  • Brachial arches
  • Projections below midbrain from face

Have migrating ectomesenchyme cells
- Can radioactively label

Depending on migration of those cells can develop a number of pathological situations – consequence on teeth formation

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7
Q

what is mandibulofacial dysostosis

A

failure of ectomesenchyme cells to migrate

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8
Q

phenotype of mandibulofacial dysostosis

A

Mandible is smaller (reduction of size)

Sometimes absence of deciduous or permanent teeth

Eyes look more apart than expected
- Lower than normal person

might have hindered/lighter presentation - some but not all phenotype

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9
Q

5 stages in tooth development

A

tooth initiation

morphogenesis

cytodifferentiation

matrix secretion

root formation

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10
Q

tooth initation

A

first stage in tooth development

Brachial arches project themselves

2 mandibular process - 2 process that join together
- Join in early stage compared to maxilla

Stomodaeum - space which forms the mouth

Primary epithelium band
develops at approx 6 wks IUL
- Appears as thickening in epithelium of embryonic mouth (stomodaeum)

Dental lamina

  • Approx. 7 wks IUL
  • The PEB has grown into the jaw
  • —Invaginating on ectomesenchyme surface

Divided into 2 parts:
- Vestibular lamina, which will break down to form the buccal sulcus, and
- The dental lamina, from which the enamel organ develops
Vestibule space is formed by apoptosis

Horse shoe shaped in structure

Tooth germs in key places where teeth form

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11
Q

primary epithelial band

A

develops at approx 6 wks IUL

- Appears as thickening in epithelium of embryonic mouth (stomodaeum)

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12
Q

dental lamina

A
  • Approx. 7 wks IUL
  • The PEB has grown into the jaw
  • —Invaginating on ectomesenchyme surface

Divided into 2 parts:
- Vestibular lamina, which will break down to form the buccal sulcus, and
- The dental lamina, from which the enamel organ develops
Vestibule space is formed by apoptosis

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13
Q

morphogenesis

A

second stage in tooth development

generation of enamel organ itself

  • bud stage (8-10 weeks)
  • cap stage (11 weeks)
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14
Q

bud stage

A

part of morphogenesis

Approx. 8–10 wks IUL

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

An ectomesenchymal condensation appears and this is the dental papilla

  • Tooth shape and structured is determined by enamel organ (first events from dental papilla)
  • Separate dental papilla and EO and place different tooth EO on top – so different tooth formed in place
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15
Q

cap stage

A

part of morphogenesis

3D cap shape of ectomesenchyme cells

Approx 11 wks IUL

The enamel organ forms a ‘cap’ over the papilla

“Cap stage” enamel organ:

  • External enamel epithelium
  • Internal enamel epithelium

EEE and IEE meet at the Cervical Loop
- Reference for root formation

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16
Q

cytodifferentiation

A

third stage in tooth development

  • bell stage (14 weeks)
  • crown pattern formation
  • permanent tooth germ (12 weeks)
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17
Q

bell stage

A

approx 14 wks IUL

More cell layers differentiated

  • 4 layers
  • —Stellate reticulum
  • —-Stratum intermedium
  • —-Internal enamel epithelium
  • —-External enamel epithelium

Tooth shape is being defined
- Seen more in incisors than molars

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18
Q

function of stellate reticulum and stratum intermedium

A

protect and maintain

stellate reticulum has nutrients present

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19
Q

4 cell layers in bell stage

A
  • stellate reticulum
  • stratum intermedium
  • internal enamel epithelium
  • external enamel epithelium
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20
Q

crown pattern formation

A

Process of forming the tooth doesn’t occur all the way through structure
- Start in teeth cusps area downwards to cervical

Dentine forming Then enamel

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21
Q

what can cause changes/disruptions in tooth formation

A

Avoid prescribing certain antibiotics to children with developing teeth

  • Tetracycline
  • —-Stains the tooth during the formation
  • —-Will show in your teeth as a line
  • —–Impregnant the content of enamel and dentine in a specific part of process of formation

Infectious disease that greatly produces fever (measles) creates specific line on toots

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22
Q

permanent tooth germ formation

A

in cytodifferentiation

At approx. 12th week, an extension appears on the lingual side of the dental lamina
- This is the dental lamina for the permanent successor

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

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23
Q

matrix secretion

A

fourth stage in tooth development

late bell stage (18 weeks)

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24
Q

late bell stage

A

Approx 18 weeks IUL

Crown shape is well defined (‘crown’ stage EO)

Apposition of enamel and dentine begins

Dental papilla cells adjacent to the IEE differentiate into odontoblasts
- Odontoblasts lay down dentine matrix, which is later mineralised

Once dentine formation has begun, IEE cells differentiate into ameloblasts, which form enamel
- EO defines the process and dental papilla follows
But Dentine formation before enamel
- For IEE to differentiate requires EO presence

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25
Q

what forms first dentine or enamel

A

Dental papilla cells adjacent to the IEE differentiate into odontoblasts
- Odontoblasts lay down dentine matrix, which is later mineralised

Once dentine formation has begun, IEE cells differentiate into ameloblasts, which form enamel

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26
Q

root formation

A

fifth stage in tooth development

Crown formation is complete before root formation begins

The enamel organ maps out the shape of the crown

The EEE and IEE meet at the cervical loop

The root shape is defined by apical growth of the cervical loop, which is now called:
- Hertwig’s epithelial root sheath

This is a 2-cell-layered structure, in contrast to the 4-layered enamel organ
- In EO need for to maintain ameloblasts (not present in root)

Hertwig’s epithelial root sheath (HERS) induces formation of root dentine
- Once the initial layer of root dentine is formed, Hertwig’s sheath breaks up (no enamel in root)
Remains of HERS persist as ‘debris of Malassez’, which may develop into a cyst
- Odontogenic cysts
Mesenchymal cells from the follicle contact the dentine, and differentiate into cementoblasts
- These form cementum
Exposure of area to cells of ectomesenchyme

Fibres from the developing PDL are embedded in the cementum (“Sharpey’s fibres”)

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27
Q

Hertwig’s epithelial root sheath

A

apical growth of the cervical loop defines root shape

2-cell-layered structure

induces formation of root dentine
- Integration of IEE and EE
migrate and differentiate into odontoblast
- Forms dentine layer - cells break apart (no enamel in root)
- Ones with contact with dentine are used to form cementoblasts
- Remains of HERS persist as ‘debris of Malassez’, which may develop into a cyst
—- Odontogenic cysts

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28
Q

what is a general term for an enamel organ

A

placode

certain genes highlighted with development process

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29
Q

what 3 other organs (bar enamel organ) are placodes

A

hair
nail
mammary gland

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30
Q

what is the common feature in placodes

A

epithelial tissue forms 4 organs with initial bud stage the same

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31
Q

hypohidrotic ectodermal dysplasia

A

Pathology

Obvious strange occurrence in teeth

  • Less teeth than expected - absence
  • Shape is different
  • —-Canin is Conoid (cone like)
  • Some of teeth are impacted —- not erupted

Changes are not only related to the teeth

  • Placode formation issue
  • —Absence of reduction in number of size or shape of teeth
  • —But also effect hair and mammary gland formation
32
Q

what type of therapy can be used for ectodemal dysplasia

A

gene therapy as it is a genetic pathology

can correct gene issue with gene replacement therapy but need to carry out in very early stage of development
- embryonic (prenatal)

33
Q

dentinogenesis

A

Ectomesenchyme cells differentiate into odontoblasts
- Odontoblast differentiation from IEE

Deposition of dentine matrix (mainly collagen)

This unmineralised dentine is predentine
- Mineralisation of dentine (hydroxyapatite)

one ectomesenchymal cell is left in waking (undifferentiated)
- stem cell

34
Q

formation of tertiary dentine

A

Formed in response of traumatic or aggressive event
Fracture, caries
- Sometimes induced by dentine
—–Remove caries partially - leave some not to expose pulp

Formed 2 ways

  • Reactionary
  • —-Odontoblast recognise threat and form tertiary dentine
  • Reparative
  • —-Aggression so harsh odontoblast dies
  • —-Dormant ectomesenchyme cells are recruited to form tertiary dentine
35
Q

what cells deposits dentine

A

odontoblasts

36
Q

primary dentine Vs secondary dentine

A

Primary while the tooth is being formed

Secondary when tooth completely formed
- Root formation 2-3 years after eruption

If formation of primary at same speed continues for secondary will close pulp area quickly
- Secondary dentine is slowed down formation

37
Q

where is the major nutritional source for the enamel organ

A

the highly vascularised dental papilla

  • need complex structure of cell layers to maintain itself as cannot reach EO
38
Q

what percentage is enamel mineralised to

A

96%

39
Q

2 basic stages of enamel formation

A

Protein matrix deposited
- Matrix is partially mineralised (30%)

Once this framework is established, the organic part is removed, and mineralisation is completed (‘maturation’)

The ameloblasts change form and function several times during amelogenesis

40
Q

what cells make enamel

A

ameloblasts

41
Q

7 ameloblasts differentiation stages (amelogenesis)

A
  1. Morphogenic
  2. Histodifferentiated
  3. Secreted (initial)
  4. Secretory (tomes)
  5. Maturative (ruffle-ended)
  6. Maturative (smooth)
  7. Protective
42
Q

why does enamel need etched

A

Crystallite more sensitive on side of crystallite
- Create a rough surface
Liquid adhesive attaches to rough surface

43
Q

direction of enamel formation

A

from the crown to cervical region (downwards)

44
Q

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
45
Q

secretory phase

A

Ameloblasts become secretory cells

They synthesise and secrete the enamel matrix proteins (amelogenins)
- Proteins organised in a way that allows super saturation

The matrix is partially mineralised (30% mineral as seeded crystallites)
- Removal of all protein allows mineral content to be increased with external introduction of calcium and phosphate

46
Q

maturation phase

A

Most of the matrix proteins are removed

Mineral content of enamel is increased

Mature enamel is 95% mineral

  • Not pure HA
  • —-Mixture carbonated apatite and HA

Fluoride presence in important

47
Q

carbonated apatite properties

A

part of mature enamel mix (carbonated and HA/FA)

Carbonated apatite is more susceptible to acid environments – removed easier

Reduced through lifetime by de- re-mineralisation process into HA and FA

48
Q

why is the use of fluoride sealant important in amelogenesis maturation stage

A

Use sealant in early stage when tooth is erupted as it is susceptible to cavity formation (facilitate and create a better environment for the teeth)

Higher risk – first permanent molar as longest exposed

No use of sealant in adult as tooth matured, diet is well established (would alter diet if need to change something)

49
Q

times of caries incidence peak

A

start primary, secondary school and uni/college

50
Q

what tooth has the highest caries risk

A

first permanent molar as longest exposed

51
Q

protection phase of amelogenesis

A

Ameloblasts regress to form a protective layer – the reduced enamel epithelium

Involved in eruption
- Formation of epithelial attachment (junctional epithelium)

52
Q

amelogenesis imperfecta

A

Autosomal recessive hypoplastic hypomaturation amelogenesis imperfecta
- Different types

Matrix metallopeptidase 20 gene or MMP20
- Located on the long (q) 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)
- Allows minerals to mature enamel and removes protein content

No Enamelysin = incorrect maturation of enamel

53
Q

phenotypic features of amelogenesis imperfecta

A

Yellow in colour than what would expect

  • Presence of protein and stain
  • Enamel translucency is based on mineral content - become more opaque

Not smooth - rough

Dull looking

Irregularities

  • due to higher failure on eating
  • More prone to chipping

Premolars look odd
- Not rounded - Formation not occurred normally

54
Q

what is the issue of stainless steel stock crowns

A

Crown is invading biological space - Stamp crown not made to space
- not suitable for permanent
teeth

Hard to restore large areas in deciduous teeth
- Enamel is more frail - weaker adhesive nature

55
Q

what is the difficulty of restoring teeth with amelogenesis imperfecta

A

enamel is not 95% mineralised

- composite doesn’t adhere to same strength

56
Q

X ray evidence of amelogenesis imperfecta (2)

A

vertical bone loss
- valley towards root - not following reach of bone

cannot see interface between enamel and dentine
- similar density as enamel decreased mineral content

57
Q

dentinogenesis imperfecta

A

enamel is properly formed

dentine doesn’t have required level of maturation

58
Q

is there a scale with amelogenesis imperfecta

A

Absence of the gene is not absolute

Genetic recession penetration is not complete (100%)

differing degrees of mineralisation

59
Q

enamel issues due to dentinogeneisis imperfecta

A

Can flex more than it should

Can cause dentine to flake and break down

60
Q

X ray evidence of dentiogenesis imperfecta

A

can see interface of enamel and dentine

since dentine is less mineralised/lower density cannot visually ID root canal

61
Q

type of tissue of enamel organ

A

epithelium

62
Q

type of tissue of dental papilla

A

ectomesenchyme

63
Q

type of tissue of dental folllicle

A

ectomesenchyme

64
Q

origin of enamel organ

A

ectoderm

65
Q

origin of dental papilla

A

neural crest

66
Q

origin of dental follicle

A

neural crest

67
Q

product of enamel organ

A

enamel

68
Q

2 products of dental papilla

A

denine

pulp

69
Q

3 products of dental follicle

A

cementum
PDL
alveolar bone (part)

70
Q

4 categories of teeth development abnormalites

A

prenatal
postnatal
inherited
acquired

71
Q

teeth development abnormalities can affect (5)

A 
number 
size
shape
structure 
eruption
72
Q

how can you tell an enamel defect is acquired and not inherited

A

line on incisal third canine to canine

Lesion couldn’t have happened in genetics as on section not whole tooth
- Permanent teeth - early stage development effected

Infectious disease potentially - measles

73
Q

gemination

A

site of one tooth but two formed

- e.g. central incisor divided into 2 right centrals

74
Q

fusion

A

2 or more teeth join together

- likely multiple roots on x-ray

75
Q

concrescence

A

connection between cementum of teeth

BDS2 BAMS (54 decks)

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