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growth and development > Tooth development > Flashcards

Tooth development Flashcards

1
Q

first sign of tooth development

A

6-7 weeks

in utero

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2
Q

when do descidusous teeth begin to calcify

A

13-20

weeks in utero

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3
Q

By_______weeks in utero all deciduous teeth

have begun to calcify

A

By 18-20 weeks in utero all deciduous teeth

have begun to calcify

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4
Q

Deciduous teeth erupt at

A

6-30 months

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5
Q

• First part of tooth to calcify is the

A

crown

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6
Q

stages of tooth development

A 
I. Crown Formation:
1. Initiation
2. Bud Stage
3. Cap Stage
4. Bell Stage
5. Enamel and dentin 
formation

II. Root Formation

III. Supporting Structures

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7
Q

NC mesenchyme in tooth development

A

NCC will migrate to PA1, contributes to the mesenchyme of tooth development/ odontogenic epithelium btwn the maxillary and mandibular processes

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8
Q

where do the max incisors form

A

medial nasal process

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9
Q

Embryonic Oral Cavity: Internal Surface of Upper & Lower Jaw
what structure is here?
gives rise to?

A

Primary Epithelial Band
 Horseshoe shaped
 Correspond to future dental arches

 Gives rise to
 Dental lamina
 Vestibular lamina

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10
Q

Early Patterning During Tooth Development, determines?

A

pattern of signaling molecules/ pathways will determine tooth morphology

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11
Q

Shh and PAX9 expression

A

Shh Is Expressed In The Epithelium And Pax9 In The Mesenchyme Where The Tooth
Bud Would Form

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12
Q

initiation stage
placode?
mesenchyme?
initial odontogenic potential? shifts?

A

 Placode formation – Epithelial thickening.
 Epithelial outgrowth into the mesenchyme

 Initial odontogenic potential lies in the epithelium subsequently shifts to mesenchyme –the neural crest mesenchyme induces the oral ectoderm to become the dental lamina

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13
Q

how does the dental lamina form? what else forms

A

epithelium invaginates into the mesenchyme, vestibular lamina forms too

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14
Q 
bud stage 
epithelial changes?
signaling molecules of placode formation?
mesenchyme at this time?
cross talk?
where is the odontogenic potential
A

 Epithelial cells show no major changes

 Shh, Lef-1 and Eda-Edar involved in placode formation (ectoderm thickening)

 Mesenchyme beneath starts to condense by the factors secreted by the epithelium

 Cross-talk between the epithelium and the mesenchyme

 Odontogenic potential in the epithelium

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15
Q

Early Cap Stage
epithelium will? mesenchyme? looks like?
tooth germ forms what structures?
transition from bud stage regulated by?

A

 Epithelium proliferates. Mesenchyme continue to condense. Looks like “Cap” sitting on a ball of
mesenchyme

 Tooth germ forms:
 Enamel organ – Enamel of the tooth
 Dental papilla – Dentin (outer) and pulp (inner)

 Bud to cap stage transition is regulated by signaling molecules and transcription factors

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16
Q

Cap Stage Enamel Knot formation/ dental follicle

A

Dental follicle or Dental Sac – Supporting structures (Cementum / Periodontium / alveolar bone
proper)
 Enamel knot – It is a key signaling center consist of cluster of non-dividing cells determines cusp
formation. Primary and secondary enamel knot

17
Q

Cap Stage Histodifferentiation
cells of enamel organ will synthesize? result?
epithelial cells become what populations?

A

Cells in the enamel organ synthesize glycosaminoglycans into the ECM. Hydrophilic and pull water into the enamel organ.

 Increase in fluid volume force the cells apart leading to formation of star shaped stellate reticulum cells

 Enamel organ epithelial cells form:
Inner enamel epithelium and Outer enamel epithelium

18
Q

Cap Stage Enamel Knot Signaling Center

main molceule/ inhibitor?

A

SHH is main molecule to signal tooth formation, inhibited by SPRY2

19
Q

bell stage
epthelium?
what layer forms?
crown?

A
  1. Under surface of the epithelium deepens and resemble a bell
  2. Stratum intermedium formation
  3. Crown attains full size and shape
20
Q

Permanent Dentition Forms_____To The Deciduous Dentition

molecule involved?

A

Lingual

Osr2 inhibits BMP4 which stimulates Msx1 to allow this

21
Q

bell stage morphodifferentiaition
cell shape/ layers?
junction of these?

A
  • Low Cuboidal shaped outer enamel epithelium (OEE)
  • Short columnar shaped inner enamel epithelium (IEE – will differentiate into ameloblasts)
  1. Junction of IEE and OEE is called cervical loop (CL) – also the future site of the CEJ
22
Q 
late bell stage 
dental lamina? 
IEE?
folding due to? 
IEE causes mesenchyme to? 
IEE dif into?
site of IEE dif determines?
A

 Dental lamina breaks and the separates the tooth from oral epithelium

 Inner enamel epithelium (IEE) completes folding forming the future crown pattern

 Folding is due to differential rates of mitotic division in IEE

 Under the influence of IEE mesenchymal cells differentiate into odontoblasts that makes
dentin

 Subsequently IEE differentiate in to ameloblasts and make enamel

 Site at which IEE differentiates determines future cusp formation

23
Q

Amelogenesis

stages?

A

Ameloblasts are derived from inner enamel epithelium and the life cycle of ameloblasts
has following stages:

  1. Morphogenetic stage
  2. Histodifferentiation stage
  3. Initial secretory stage (no Tome’s process)
  4. Secretory stage (Tome’s process)
  5. Ruffle ended ameloblast of the maturation stage
  6. Smooth ended ameloblast of the maturation stage
  7. Protective stage
24
Q

Secretory Stage Ameloblasts
activities?
forms?
secrete? contents?

A

 Intense synthetic and secretory activity

 Forms enamel rod (R) and inter-rod (IR)

 Secrete granules on the newly formed mantle dentin.

 Secretory products:

 Proteins:
 Amelogenin
 Ameloblastin
 Enamelin

 Proteases
 Enamelysin (MMP20)
 Kallikrein

25
Q

Under the influence of ______cells
__________ cells differentiate into
odontoblasts that make dentin

A

epithelial

mesenchymal

26
Q

Types of Dentin

A
  1. Mantle dentin – First layer of dentin formed by the newly
    differentiated odontoblasts, hypomineralized, and only in the
    crown of the tooth (30-50um thick)
  2. Primary dentin – Formed during tooth development (4um/day)
  3. Secondary dentin – Dentin formed after tooth eruption
    (0. 4um/day)
  4. Tertiary dentin – Dentin produced in response to injury to
    protect the pulp
27
Q

Enamel and Dentin Formation diagrammed

A
28
Q

Root Formation
IEE/OEE?
odontoblasts?

A

 IEE and OEE form the cervical loop proliferate downward to form double layered structure called Hertwig’s epithelial root sheath, also the site of the CEJ

 Odontoblasts differentiation and dentin formation

 Completion of root formation

29
Q 
Cementum Formation
Fragmentation of Hertwigs?
cementoblasts from? 
remnants of HERS? 
cementum cellularity?
A

 Fragmentation of Hertwigs epithelial root sheath (HERS), mostly removed before cementum is
laid down

 Differentiation of cementoblasts from HERS or dental follicle cells

 Remnants of HERS are called epithelial rests of Malassez

 Cementum: Acellular or Cellular

30
Q

types of CEJ

A

overlapped
adjacent
no overlap

31
Q

Periodontal Ligament Formation

A

occurs will root formation, several different kinds of fibers formed

32
Q

epithelium development path

A
33
Q

mesenchyme development path

A

growth and development (14 decks)

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