Tooth Development: Putting it all together

Question 1

Timing of deciduous

dentition (2)

Answer 1

• Eruption and
exfoliation
• Sequence of eruption

Question 2

Timing of permanent

dentition (5)

Answer 2

• When the crown
begins to calcify
• When the crown is
completely calcified
• Completion of root
development
• Eruption
• Sequence of eruption

Question 3

First sign of tooth development is at

Answer 3

6-7 weeks

in utero

Question 4

• Deciduous teeth begin to calcify at

Answer 4

13-20

weeks in utero

Question 5

By —- all deciduous teeth

have begun to calcify

Answer 5

18-20 weeks in utero

Question 6

• Deciduous teeth erupt at

Answer 6

6-30 months

Question 7

• First part of tooth to calcify is the

Answer 7

crown

Question 8

Stages of Tooth Development (3)

Answer 8

I. Crown Formation:
II. Root Formation
III. Supporting Structures

Question 9

I. Crown Formation: (5)

Answer 9

1. Initiation
2. Bud Stage
3. Cap Stage
4. Bell Stage
5. Enamel and dentin
   formation

Question 10

Primary Epithelial Band (2)

Answer 10

 Horseshoe shaped
 Correspond to future
dental arches

Question 11

Primary Epithelial Band

Gives rise to (2)

Answer 11

 Dental lamina

 Vestibular lamina

Question 12

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

Answer 12

Epithelium

Mesenchyme

Question 13

Initiation of Tooth

Development (3)

Answer 13

 Placode formation 
 Epithelial outgrowth into
the mesenchyme
 Initial odontogenic
potential lies in the
epithelium subsequently
shifts to mesenchyme

Question 14

Placode formation –

Answer 14

Epithelial thickening.

Question 15

Initial odontogenic
potential lies in the
epithelium subsequently
shifts to mesenchyme –

Answer 15

the neural crest
mesenchyme induces
the oral ectoderm to
become the dental
lamina

Question 16

Bud Stage (5)

Answer 16

 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

Question 17

Cap Stage

Answer 17

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

Question 18

Tooth germ: (2)

Answer 18

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

Question 19

Bud to cap stage transition is

regulated by

Answer 19

signaling molecules

and transcription factors

Question 20

Dental follicle or Dental Sac –

Answer 20

Supporting structures (Cementum / Periodontium / alveolar bone
proper)

Question 21

Enamel knot –

Answer 21

It is a key signaling center consist of cluster of non-dividing cells determines cusp
formation. Primary and secondary enamel knot

Question 22

Cap Stage Histodifferentiation
Cells in the enamel organ synthesize
--- in to the ECM.
Hydrophilic and pull water in to
enamel organ.

Answer 22

glycosaminoglycans

Question 23

Cap Stage Histodifferentiation
Increase in fluid volume force the
cells apart leading to formation of

Answer 23

star shaped stellate reticulum cells

Question 24

Enamel organ epithelial cells (2)

Answer 24

 Inner enamel epithelium

 Outer enamel epithelium

Question 25

Bell Stage: (3)

Answer 25

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

Question 26

Bell Stage (2)

Answer 26

1. Morphodifferentiation 2. Junction of IEE and OEE is called cervical loop (CL) – also the future site of the CEJ

Question 27

Bell Stage | 1. Morphodifferentiation (2)

Answer 27

``` • Low Cuboidal shaped outer enamel epithelium (OEE) • Short columnar shaped inner enamel epithelium (IEE – will differentiate into ameloblasts) ```

Question 28

Late Bell Stage | 2

Answer 28

 Dental lamina breaks and the separates the tooth from oral epithelium  Inner enamel epithelium (IEE) completes folding forming the future crown pattern

Question 29

Late Bell Stage | Folding is due to

Answer 29

differential rates of mitotic | division in IEE

Question 30

Late Bell Stage Under the influence of IEE mesenchymal cells differentiate into

Answer 30

odontoblasts that makes | dentin

Question 31

Late Bell Stage | Subsequently IEE differentiate in to

Answer 31

ameloblasts and make enamel

Question 32

Late Bell Stage | Site at which IEE differentiates determines

Answer 32

future cusp formation

Question 33

Ameloblasts are derived from

Answer 33

inner enamel | epithelium

Question 34

Ameloblasts are derived from inner enamel epithelium and the life cycle of ameloblasts has following stages: (7)

Answer 34

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

Question 35

Secretory Stage Ameloblasts |  Intense (2) activity

Answer 35

synthetic and secretory

Question 36

Secretory Stage Ameloblasts |  Forms (2)

Answer 36

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

Question 37

Secretory Stage Ameloblasts  Secrete --- on the newly formed mantle dentin.

Answer 37

granules

Question 38

Secretory Stage Ameloblasts | Secretory products: (2)

Answer 38

 Proteins: |  Proteases

Question 39

Proteins: (3)

Answer 39

 Amelogenin  Ameloblastin  Enamelin

Question 40

Proteases (2)

Answer 40

 Enamelysin (MMP20) |  Kallikrein

Question 41

Under the influence of epithelial cells | mesenchymal cells differentiate into

Answer 41

odontoblasts that make dentin

Question 42

Mantle dentin –

Answer 42

First layer of dentin formed by the newly differentiated odontoblasts, hypomineralized, and only in the crown of the tooth (30-50um thick)

Question 43

Primary dentin –

Answer 43

Formed during tooth development (4um/day)

Question 44

Secondary dentin –

Answer 44

Dentin formed after tooth eruption | 0.4um/day

Question 45

Tertiary dentin –

Answer 45

Dentin produced in response to injury to | protect the pulp

Question 46

``` Tooth Development: Root Formation IEE and OEE form the cervical loop proliferate downward to form double layered structure called ---, also the site of the CEJ ```

Answer 46

Hertwig’s epithelial root | sheath

Question 47

Tooth Development: Root Formation (2)

Answer 47

```  Odontoblasts differentiation and dentin formation  Completion of root formation ```

Question 48

--- mostly removed before cementum is laid down

Answer 48

Fragmentation of Hertwigs epithelial root sheath (HERS),

Question 49

Tooth Development: Cementum | Formation

Answer 49

Differentiation of cementoblasts from HERS or dental follicle cells

Question 50

Tooth Development: Cementum Formation Remnants of HERS are called

Answer 50

epithelial | rests of Malassez

Question 51

``` Cementum types (2) ```

Answer 51

 Acellular |  Cellular