OCB02-1010 Late tooth development

Question 1

Where is the PEK formed?

Answer 1

Right in centre of the enamel organ in the IEE

Question 2

When is the PEK formed?

Answer 2

Cap stage

Question 3

What does it mean by the cells in the PEK are ‘non-proliferative’?

Answer 3

Cells in the PEK do not divide

Question 4

What signalling molecules do the PEK secrete?

Answer 4

BMPs, FGFs, Wnts, Shh

Question 5

What is the Enamel knot known as?

Answer 5

The ‘signalling centre’ as it doesn’t contain receptors

Question 6

What cusp does the PEK mark the position of in molars?

Answer 6

The first bucker cusp of the molars

Question 7

What occurs in the early bell stage?

Answer 7

The IEE has further invaginated

The stellate reticulum has expanded

Question 8

What is the enamel cord?

Answer 8

A string of epithelial cells that links the inner and outer epithelium on the monocuspid and mutlicuspid

Question 9

What are the 3 layers of the dental follicle?

Answer 9

Inner layer
Loose connective tissue layer
outer layer

Question 10

What layers form the periodontal ligament?

Answer 10

outer and inner

Question 11

Where do secondary enamel knots appear?

Answer 11

In multicuspid teeth

Question 12

What do the numbers of SEK determine?

Answer 12

Number of cusps

Question 13

What is a successional tooth?

Answer 13

Permanent tooth with a tooth predecessor

Question 14

What is an accessional tooth?

Answer 14

Permanent tooth with no predecessor

Question 15

What happens to the dental lamina in the late bell stage?

Answer 15

It breaks down

Question 16

What remains after the dental lamina breaks down? and what can they cause?

Answer 16

Some epithelial clusters called epithelial pearls of Serres

These can cause cysts odontomas (tumours) or supernumerary teeth

Question 17

Why do humans have only 2 dentitions?

Answer 17

The dental lamina contains the stem cells that are able to produce new teeth
Therefore after the second dentition has formed, the dental lamina breaks down and prevents the formation of new teeth

Question 18

What are monophyodont beings?

Answer 18

Mouse, chameleon

Single generation of teeth, no replacement

Question 19

What are diphyodont beings?

Answer 19

Humans

SEcond generation of teeth

Question 20

What are polyphyodont beings?

Answer 20

snakes

multiple generation of teeth

Question 21

What is histogenesis?

Answer 21

The terminal differentiation of specialised cells that gives rise to fully formed dental tissues

Question 22

What is mineralised tissue?

Answer 22

Enamel, dentin

Question 23

What is non-mineralised tissue?

Answer 23

Dental pulp

Question 24

When does formation of hard tissues begin?

Answer 24

Late bell stage

Question 25

What do cells at the periphery of the dental papilla differentiate into?

Answer 25

Odontoblasts

Question 26

What do odontoblasts do?

Answer 26

Secrete predentin, which is mineralised into dentin

Question 27

What cells do the IEE differentiate into?

Answer 27

Ameloblasts

Question 28

What do ameloblasts do?

Answer 28

Lay down enamel

Question 29

How do ameloblasts and odontoblasts diffrentiate?

Answer 29

There is elongation and polarisation of the IEE
This causes diffrentiation of odontoblasts
They lay down one layer of predentin which send signals to the pre-ameloblasts to become ameloblasts
The ameloblasts become fully functional
They then begin to lay down enamel

Question 30

Why do ameloblasts not get nutrients from blood vessels in mesenchyme within dental papilla?

Answer 30

When odontoblasts lay down predentin and dentin, there will be a barrier between the odontoblasts and ameloblasts
The ameloblasts will not get nutrients for the dental pulp anymore

Question 31

How do ameloblasts get nutrients?

Answer 31

When mineralising occurs at the tip of the cusp during amelogenesis, the stellate reticulum collapses
Outside the epithelial bell, are mesenchyme which contains blood vessels for nutrient diffusion