Tooth Development

Question 1

What is the structure of a tooth?

Answer 1

Enamel layer 
Amelodentinal junction
Dentine
Pulp
Cementum

Question 2

What is the make up of enamel?

Answer 2

96% mineral
1-2% matrix
2% water

Question 3

What is the make up of dentine?

Answer 3

70% mineral
20% matrix
10% water

Question 4

What is the make up of cementum?

Answer 4

65% mineral
23% matrix
12% water

Question 5

What is the make up of bone?

Answer 5

60% mineral
25% matrix
15% water

Question 6

Properties of enamel

Answer 6

Covers anatomical crown
Epithelial product
96% inorganic
2mm thick max
Translucent
Non-vital
Hard
Brittle

Question 7

Properties of dentine

Answer 7

Specialised connective tissue
Hard
Strong and resilient
70% mineral 20% organic
Collagen
Dentinal tubules

Question 8

Properties of cementum

Answer 8

Mineralised tissue
Mineralised connective tissue
Covers tooth roots
Tooth support
Resistant to resorption

Question 9

What do epithelial interactions give rise to?

Answer 9

Enamel

Hyaline layer of root

Question 10

What do mesenchyme interactions give rise to?

Answer 10

Dentine
Pulp
Cementum
Periodontium

Question 11

When is the first signs of tooth development?

Answer 11

6 weeks

Question 12

Stages of the tooth germ

Answer 12

Bud Stage
Cap Stage
Bell Stage
Crown Stage

Question 13

What happens at the bud stage?

Answer 13

Spherical/ovoid epithelial condensation
Cell proliferation
No histodifferentiation or morphogenesis

Question 14

What happens at the cap stage?

Answer 14

Cap shaped enamel organ
Poorly histodifferentiated
Little morphogenesis

Question 15

What happens late cap stage?

Answer 15

Some histodifferentiation (inner and outer enamel epithelia)
Some morphogenesis

Question 16

What happens at the early bell stage?

Answer 16

Enamel organ:
- Inner enamel epithelium forms amaloblasts
- stratum intermedium
- stellate reticulum
- outer enamel epithelium
Ectomesenchyme
- dental papilla forms odontoblasts and pulp
- dental follicle forms cementum, PDL and bone

Question 17

Dentinogenesis

Answer 17

Cytodifferentiation
- dental papilla cells form odontoblasts
Matrix formation
- odontoblasts produce collagen rich predentine
- odontoblasts retreat inwards
- odontoblasts have a long cell process forming dentinal tubule
Mineralisation
- predentine mineralises forming dentine

Question 18

Amelogenesis

Answer 18

Inner enamel epithelium form ameloblasts
Ameloblast secrete enamel protein matrix
Virtually immediate mineralisation
- 15% mineral, 65% water, 20% proteins
- rapid increase to 30% mineral = immature enamel
Gradual maturation 
- further mineralisation to 96%
- requires removal of most of the enamel proteins

Question 19

What happens at the crown stage?

Answer 19

Dentinogenesis and amelogenesis

Question 20

Root formation

Answer 20

Root = dentine and cementum

Dentine and cementum derived from ectomesenchyme so requires epithelial signal for initiation