OCB02-1009 Early tooth development

Question 1

What stages are involved in morphogenesis?

Answer 1

bud
cap
bell

Question 2

Where do the upper incisors develop from?

Answer 2

the frontonasal process

Question 3

Where do all the upper teeth except for the incisors develop from?

Answer 3

the maxillary process

Question 4

Where do all of the lower teeth develop from?

Answer 4

the mandibular arch

Question 5

Where did the epithelium derive from?

Answer 5

The ectoderm

Question 6

Where did mesenchyme derive from?

Answer 6

cranial neural crest cells

Question 7

What does the epithelium give rise to?

Answer 7

enamel

Question 8

What does the mesenchyme give rise to?

Answer 8

dentin, dental pulp, cementum, periodontal ligament, alveolar bone socket

Question 9

How do cranial neural cells form ectomesenchyme?

Answer 9

They delaminate at the border of the neural and non-neural ectoderm
CnCCs undergo an epithelial to mesenchyme transition
This gives rise to cells known as the ectomesencyme

Question 10

How is ecotmesenchyme different from mesenchyme?

Answer 10

Because ectomesenchyme arises from neural crest cells

Question 11

What happens to the mesenchyme that is formed by CNCCs?

Answer 11

The mesenchyme migrate towards the first brachial arch to fill the ventral part of the face and gives rise to swellings

Question 12

Where does the first brachial arch receive CNCCs from?

Answer 12

rhombomeres 1 and 2 from the hindbrain and some from the midbrain

Question 13

What is treacher collins syndrome?

Answer 13

Mutation if the TCOF1 gene, which is essential for NCC survival
If there is not enough CNCC, not enough teeth will be made

Question 14

Where is oral epithelium present?

Answer 14

It covers the present oral cavity, the first brachial arch, the maxillary process and the frontonasal process

Question 15

What gene is expressed in the epithelium the covers the first brachial arch, maxillary process and mandibular process?

Answer 15

Pitx2 gene

Question 16

What gene gives rise to multicusped teeth?

Answer 16

Barx1

Question 17

What occurs in the initiation stage?

Answer 17

A continuous band of thickened epithelium known as the primary epithelial band forms on the upper and lower jaw
It invaginates into the underlying mesenchyme
The primary epithelial band corresponds to a thickening of the oral epithelium.
The thickening process is due to a change in orientation of the cells, they go from parallel to perpendicular

Question 18

What are the two subdivisions of the primary epithelial band?

Answer 18

The dental lamina, which connects the developing tooth bud to the oral epithelium
Vestibular lamina, of which cells die to give rise to the space between the teeth and lips or inner cheek

Question 19

When does the formation of dental lamina occur?

Answer 19

6-7th week

Question 20

What is tooth agenesis?

Answer 20

Mesenchyme does not condense properly at bud stage

Question 21

What occurs during the bud stage?

Answer 21

A series of swelling on the surface of the dental lamina make way for deciduous teeth
Each one of the swellings is known as a dental placode that makes way for a tooth
As the swellings are created, a signal is sent to the mesenchyme to induce Pax9 gene expression, which labels the sites involved in tooth development

Question 22

What will happen if Pax9 is not expressed correctly?

Answer 22

The tooth will remain at the bud stage

Question 23

What is the dental mesenchyme?

Answer 23

The mesenchyme which condenses around the enamel

Question 24

What is the enamel organ?

Answer 24

The epithelial bud which only gives rise to the enamel

Question 25

What make up the tooth germ?

Answer 25

The dental mesenchyme and epithelial bud

Question 26

What happens during the cap stage?

Answer 26

A small group of ectomesenchymal cells stop producing extracellular substances, which results in an aggregation of these cells called dental papillae
Blood vessels grow in the dental follicles and enter the dental papilla at the cap stage
At this point, the tooth bud grows around the ectomesenchymal aggregation and becomes the enamel organ

Question 27

What is the dental follicle?

Answer 27

The condensation of ectomesenchymal cells that surrounds the enamel organ and limits the growth of the dental papilla

Question 28

What are the two populations of condensed mesenchyme?

Answer 28

Dental follicle and dental papilla

Question 29

What does the dental papilla give rise to?

Answer 29

Dentin and dental pulp

Question 30

What does the dental follicle give rise to?

Answer 30

cementum, periodontal ligament and alveolar bone socket

Question 31

What are the different cell types in the enamel organ?

Answer 31

Outer enamel epithelium: cuboidal cells
Inner enamel epithelium: columnar cells
Stellate reticulum: cells in the centre of the cap
Stratum intermedium: lines the inside of the inner enamel epithelium