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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
what forms first dentine or enamel
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
26
root formation
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”)
27
Hertwig’s epithelial root sheath
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
28
what is a general term for an enamel organ
placode certain genes highlighted with development process
29
what 3 other organs (bar enamel organ) are placodes
hair nail mammary gland
30
what is the common feature in placodes
epithelial tissue forms 4 organs with initial bud stage the same
31
hypohidrotic ectodermal dysplasia
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
what type of therapy can be used for ectodemal dysplasia
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
dentinogenesis
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
formation of tertiary dentine
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
what cells deposits dentine
odontoblasts
36
primary dentine Vs secondary dentine
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
where is the major nutritional source for the enamel organ
the highly vascularised dental papilla - need complex structure of cell layers to maintain itself as cannot reach EO
38
what percentage is enamel mineralised to
96%
39
2 basic stages of enamel formation
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
what cells make enamel
ameloblasts
41
7 ameloblasts differentiation stages (amelogenesis)
1. Morphogenic 2. Histodifferentiated 3. Secreted (initial) 4. Secretory (tomes) 5. Maturative (ruffle-ended) 6. Maturative (smooth) 7. Protective
42
why does enamel need etched
Crystallite more sensitive on side of crystallite - Create a rough surface Liquid adhesive attaches to rough surface
43
direction of enamel formation
from the crown to cervical region (downwards)
44
ameloblast differentiation
Dentine induces IEE cells to differentiate into ameloblasts - they elongate, becoming columnar - the nucleus migrates to the basal end of the cell
45
secretory phase
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
maturation phase
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
carbonated apatite properties
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
why is the use of fluoride sealant important in amelogenesis maturation stage
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
times of caries incidence peak
start primary, secondary school and uni/college
50
what tooth has the highest caries risk
first permanent molar as longest exposed
51
protection phase of amelogenesis
Ameloblasts regress to form a protective layer – the reduced enamel epithelium Involved in eruption - Formation of epithelial attachment (junctional epithelium)
52
amelogenesis imperfecta
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
phenotypic features of amelogenesis imperfecta
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
what is the issue of stainless steel stock crowns
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
what is the difficulty of restoring teeth with amelogenesis imperfecta
enamel is not 95% mineralised | - composite doesn't adhere to same strength
56
X ray evidence of amelogenesis imperfecta (2)
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
dentinogenesis imperfecta
enamel is properly formed dentine doesn't have required level of maturation
58
is there a scale with amelogenesis imperfecta
Absence of the gene is not absolute Genetic recession penetration is not complete (100%) differing degrees of mineralisation
59
enamel issues due to dentinogeneisis imperfecta
Can flex more than it should Can cause dentine to flake and break down
60
X ray evidence of dentiogenesis imperfecta
can see interface of enamel and dentine since dentine is less mineralised/lower density cannot visually ID root canal
61
type of tissue of enamel organ
epithelium
62
type of tissue of dental papilla
ectomesenchyme
63
type of tissue of dental folllicle
ectomesenchyme
64
origin of enamel organ
ectoderm
65
origin of dental papilla
neural crest
66
origin of dental follicle
neural crest
67
product of enamel organ
enamel
68
2 products of dental papilla
denine | pulp
69
3 products of dental follicle
cementum PDL alveolar bone (part)
70
4 categories of teeth development abnormalites
prenatal postnatal inherited acquired
71
teeth development abnormalities can affect (5)
``` number size shape structure eruption ```
72
how can you tell an enamel defect is acquired and not inherited
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
gemination
site of one tooth but two formed | - e.g. central incisor divided into 2 right centrals
74
fusion
2 or more teeth join together | - likely multiple roots on x-ray
75
concrescence
connection between cementum of teeth

BDS2 BAMS (54 decks)

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