Late Tooth Development

Question 1

What are the stages of late tooth development?

Answer 1

Cap

Bell

Eruption

Question 2

When does tooth shape formation/determination begin?

Answer 2

Cap stage

Question 3

Where is the primary enamel knot?

Answer 3

Sits above inner enamel epithelium

Question 4

When does the primary enamel knot appear?

Answer 4

Bud stage

Question 5

What is the role of the PEK and how does it do this?

Answer 5

Influence proliferation and differentiation of cells of tooth germ by releasing signalling molecules

Juxtaposition of non-proliferative PEK cells with the surrounding proliferating cells drives bending of the inner enamel epithelium

Question 6

Why doesn’t the PEK proliferate in response to its own secretions?

Answer 6

Does not have receptors for its own signalling molecules

Question 7

When is the primary enamel knot present and how is it eliminated?

Answer 7

Bud and cap stage

Apoptosis

Question 8

In the molars, what does the PEK mark the position of?

Answer 8

First buccal cusp

Question 9

When is the bell stage?

Answer 9

14th-20th week

Question 10

What is the enamel cord?

Answer 10

String of epithelial cells joining the inner and outer enamel epithelia

Question 11

What does the enamel cord look like?

Answer 11

Darkened area joining IEE and OEE

Causes a dip in OEE

Question 12

What happens to the cervical loop?

Answer 12

Becomes Hertwig’s epithelial root sheath for root formation

Question 13

What are the three basic layers of the dental follicle (bell stage)?

Answer 13

Outer layer

Loose connective tissue

Inner layer

Question 14

Compare the layers of the dental follicle (bell stage).

Answer 14

Outer and inner layers are more vascularised and have more closely packed cells than the loose connective tissue layer

Question 15

What part of the tooth germ gives rise to the PDL?

Answer 15

Dental follicle

Question 16

When is the tooth crown shape established?

Answer 16

Bell stage

Question 17

In what type of teeth do SEKs form?

Answer 17

Multicuspid

Question 18

When do the SEKs form?

Answer 18

Bell stage

Question 19

Which SEKs will form larger cusps?

Answer 19

Those which emerge earlier

Question 20

When do tooth buds for permanent teeth start to form?

Answer 20

Late bell stage/20th week

Question 21

Where does the successional lamina develop?

Answer 21

Lingual side of dental lamina

Question 22

Are the deciduous teeth more buccal or lingual than the permanent teeth?

Answer 22

Buccal

Question 23

What kind of lamina does a successional tooth develop from?

Answer 23

Successional

Question 24

What do the three permanent molars develop from?

Answer 24

Dental lamina extends backward when there is enough space

All from the same placode

Question 25

What is a successional tooth?

Answer 25

Permanent tooth with a predecessor

Question 26

What is an accessional tooth?

Answer 26

Permanent tooth with no predecessor

Question 27

When does the dental lamina begin to break down?

Answer 27

Late bell stage/20th week

Question 28

Why does the dental lamina break down?

Answer 28

Separate tooth germs from the oral epithelium

Question 29

Why are humans usually diphyodonts?

Answer 29

Dental lamina contains stem cells to give rise to new teeth DL breaks down at late bell stage/20th week so no continuous generation

Question 30

What are the epithelial pearls of Serres?

Answer 30

Epithelial clusters remaining after breakdown of dental lamina

Question 31

What implications can the epithelial pearls of Serres cause? (3)

Answer 31

Cysts Odontomas Supernumerary teeth

Question 32

Give an example of a monophyodont.

Answer 32

Mouse Chameleon

Question 33

Give an example of a polyphyodont.

Answer 33

Snake Shark

Question 34

Why do some animals have multiple sets of teeth?

Answer 34

Permanent dental lamina can give rise to more successional laminas for the formation of more teeth

Question 35

How can you cause continuous tooth generation in mice?

Answer 35

Activation of Wnt/β-catenin signalling

Question 36

What is Wnt/β-catenin?

Answer 36

Growth factor

Question 37

Where is Wnt signalling concentrated in snakes?

Answer 37

Successional lamina of regenerating teeth

Question 38

What can be used to stimulate Wnt signalling?

Answer 38

LiCl

Question 39

What does overexpression of the Wnt pathway result in?

Answer 39

Increased number of teeth

Question 40

When does the formation of hard tissues begin?

Answer 40

Late bell stage/20th week

Question 41

Where does the formation of hard tissues begin?

Answer 41

Tip of cusp(s)

Question 42

What do ameloblasts produce?

Answer 42

Enamel (matrix)

Question 43

What do odontoblasts produce?

Answer 43

Predentin

Question 44

What tissue are ameloblasts derived from?

Answer 44

Inner enamel epithelium

Question 45

What tissue are odontoblasts derived from?

Answer 45

Periphery of dental papilla/pulp

Question 46

What is happening to the outer layer of the dental follicle during the bell stage?

Answer 46

Differentiating into alveolar bone

Question 47

Why does the stellate reticulum collapse during hard tissue formation?

Answer 47

Hard tissue (matrix) acts as a barrier of nutrients and oxygen getting to the ameloblasts Allows ameloblasts to get get nutrients from mesenchyme outside outer enamel epithelium

Question 48

Describe the cell differentiation and hard tissue formation process. (3)

Answer 48

1. Elongation and polarisation of inner enamel epithelium to preameloblasts 2. Preameloblasts trigger elongation and polarisation of pulpal cells to odontoblasts which secrete predentin 3. Predentin triggers preameloblasts to become ameloblasts