Formation of the Dental Hard Tissues Part 2: Amelogenesis

Question 1

What is the enamel components?

Answer 1

Mineralised Epithelial product

96% mineral – Hydroxyapatite

1-2% organic matrix – Enamel proteins – NOT collagen etc.

2% water

Starts to form after dentine mineralises

Question 2

What is labelled?

Answer 2

Question 3

What is the orange area?

Answer 3

Predentine

Question 4

What is labelled?

Answer 4

Question 5

Answer 5

Question 6

Answer 6

Question 7

Answer 7

Question 8

What is the final trigger for Amelogenesis?

Answer 8

• Dentine formation
• Breakdown of basal lamina

Question 9

What are the enamel proteins in the organic matrix?

Answer 9

• amelogenins (90%)
• enamelins - (~2%) strongly binds to mineral
• tuftelin - confined to ADJ

Question 10

What are Amelogenins?

Answer 10

• Rich in proline and glutamine
• Similar in different species – clinically useful
• Hydrophobic – aggregate
• Spread throughout the developing enamel thickness
• Thixotropic

Question 11

What is the Role of enamel proteins?

Answer 11

• Aid nucleation of hydroxyapatite – epitactic matrix
• Orientate + stabilise crystal growth
• Broken down and lost during maturation

Question 12

Maturation is when Thin crystals grow in thickness during further Enamel mineralisation. What does maturation require?

Answer 12

Requires:

– Mineral ions IN

– enamel matrix OUT

Question 13

What is the The matrix that flows out and the matrix that remains?

Answer 13

The matrix that flows out - amelogenins

The matrix that remains- enamelin

Question 14

What is the enamel cuticle?

Answer 14

formed when maturation is ~complete

Final ameloblast secretion - the enamel cuticle

Question 15

Reduced enamel epithelium forms when enamel formation is complete, What is its function?

Answer 15

1. protection of enamel surface from: • resorption • prevention of cementum formation
2. provide an epithelial lined pathway for eruption
3. Forms initial junctional epithelium…