Early Tooth Development

Question 1

What are the stages of early tooth development?

Answer 1

(Resting/dental lamina)

Initiation

Bud stage

Cap stage

Question 2

What are the embryonic origins of the teeth?

Answer 2

Epithelium of first branchial arch and frontal nasal process

Question 3

What is the embryonic origin of the upper deciduous incisors?

Answer 3

Frontal nasal process

Question 4

What part of the tooth does the oral epithelium develop into?

Answer 4

Enamel

Question 5

What parts of the tooth does the oral mesenchyme develop into? (5)

Answer 5

Dentin

Dental pulp

Cementum

PDL

Alveolar bone

Question 6

Where do the cranial neural crest cells for the first pharyngeal arch come from?

Answer 6

Midbrain and rhombomeres 1 and 2

Question 7

What can neuroblasts differentiate into? (2)

Answer 7

Motor or sensory neurons

Sympathetic neurons

Question 8

What can ectomesenchymal cells differentiate into? (5)

Answer 8

Chondroblasts

Cementoblasts

Odontoblasts

Osteoblasts

Fibroblasts

Question 9

What syndrome does a mutation in Tcof1 cause?

Answer 9

Treacher-Collins syndrome

Question 10

Why is Tcof1 important?

Answer 10

Essential for neural crest cell survival

Question 11

What are some of the possible defects in structures derived from the first two branchial arches? (5)

Answer 11

Hypoplastic maxilla and mandible

Lower eyelid coloboma

Cleft palate

Ear defects - poorly developed or misplaces

Tooth agenesis

Question 12

Where is Pitx2 expressed?

Answer 12

Dental oral epithelium

Question 13

Where is Barx1 expressed?

Answer 13

Dental mesenchyme

Question 14

Where is Pax9 expressed?

Answer 14

Dental mesenchyme

Question 15

Where is Lhx5/6 expressed?

Answer 15

Dental mesenchyme

Question 16

What do Pitx2, Barx1, Pax9 and Lhx5/6 code for?

Answer 16

Transcription factors

Question 17

What are the two tissues involved in tooth development?

Answer 17

Oral ectoderm/epithelium

Ectomesenchyme/dental mesenchyme

Question 18

What is initiation?

Answer 18

Establishment of the sites of the future teeth

Question 19

When does the primary epithelial band form?

Answer 19

6th week

Question 20

What is the primary epithelial band?

Answer 20

Continuous band of thickened epithelium along oral side of maxilla and mandible

Question 21

How does the primary epithelial band form?

Answer 21

Change in orientation of cleavage plane of dividing cells

Question 22

When does the dental lamina form?

Answer 22

6th-7th week

Question 23

What does the primary epithelial band give rise to?

Answer 23

Vestibular lamina

Dental lamina

Question 24

Is the dental lamina more buccal or lingual than the vestibular lamina?

Answer 24

Lingual

Question 25

What happens to the vestibular lamina?

Answer 25

Cells die to form empty space/vestibule

Question 26

What happens to the dental lamina?

Answer 26

Forms teeth

Question 27

When does tooth formation actually start?

Answer 27

8th week

Question 28

What happens at the very start of tooth formation?

Answer 28

Series of swellings develop on the deep surface of the dental lamina (10 on each arch) - dental placodes

Question 29

What are dental placodes?

Answer 29

Swellings that develop on the deep surface of the dental lamina at the start of tooth formation

Question 30

Why do 10 dental placodes develop on each arch?

Answer 30

10 deciduous teeth on each arch

Question 31

Which gene is expressed in the mesenchyme associated with dental placodes?

Answer 31

Pax9

Question 32

What happens to the dental placodes?

Answer 32

Expand into buds due to increased proliferation

Question 33

When is the bud stage?

Answer 33

8th-10th week

Question 34

What is the tooth germ comprised of?

Answer 34

Enamel organ and dental mesenchyme

Question 35

What can occur in patients with a Pax9 or MSX1 mutation?

Answer 35

Tooth development arrested at bud stage

Question 36

What determines the crown shape?

Answer 36

Folding of inner enamel epithelium

Question 37

When is the cap stage?

Answer 37

11th-12th week

Question 38

What can the condensed mesenchyme be divided into?

Answer 38

Dental follicle Dental papilla

Question 39

What is derived from the dental follicle?

Answer 39

Cementum PDL Alveolar bone socket

Question 40

What is derived from the dental papilla?

Answer 40

Dentin Dental pulp

Question 41

What are the four tissues which make up the enamel organ?

Answer 41

Outer enamel epithelium Stellate reticulum Stratum intermedium Inner enamel epithelium

Question 42

Describe the cells of the outer enamel epithelium.

Answer 42

Cuboidal

Question 43

Describe the cells of the inner enamel epithelium.

Answer 43

Columnar

Question 44

Describe the stellate reticulum.

Answer 44

Star-shaped cells Lots extracellular matrix = loose tissue

Question 45

What is the stratum intermedium?

Answer 45

Flat cells lining the inner enamel epithelium