amelogenesis

Question 1

describe enamel

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

describe enamel spindle formation

Answer 2

nucleus of ameloblast polarises, goes to one size odontoblast process may enter enamel epithelium

Question 3

describe enamel prisms

Answer 3

enamel prism shape governed:
- by the tomes process
- direction of migration of the ameloblast
regions formed without a tomes process are aprismatic:
- 1st formed (i.e. innermost) 5micrometres
- last formed (i.e. outmost) 30micrometres

Question 4

what is the final cue for onset for amelogenesis?

Answer 4

• dentine formation
• breakdown of basal lamina

Question 5

Ameloblast

Answer 5

• secretes organic matrix
• immediate partial mineralisation

Question 6

amelogenesis maturation by?

Answer 6

• influx of mineral ions
• breakdown and removal of most of the organic matrix

Question 7

describe enamel matrix (an epithelial product)

Answer 7

organic matrix: amorphous gel
enamel proteins:
- amelogenins (90%)
- enamelins - (~2%) strongly binds to mineral
- tuftelin - confined to ADJ
- enzymes

Question 8

describe amelogenins

Answer 8

• Rich in proline and glutamine
• similar in different species - clinically useful
• hydrophobic - aggregate
• spread throughout the developing enamel thickness
• thixotropic

Question 9

what is the role of enamel proteins?

Answer 9

• aid nucleation of hydroxyapatite
  epitactic matrix
• orientate + stabilise crystal growth
• broken down and lost during maturation

Question 10

what is enamelins?

Answer 10

• the matrix that flows out - amelogenins
• the matrix that remains - enamelin

Question 11

describe enamel cuticle

Answer 11

• formed when maturation is complete
• final ameloblast secretion - the enamel cuticle

Question 12

describe reduced enamel epithelium

Answer 12

• forms when enamel formation is complete
  derived from:
• reduced ameloblasts
• other remmants of the enamel organ OEE etc
• attached to the cuticle

Question 13

what is the function of the reduced enamel epithelium ?

Answer 13

1) protection of enamel surface from:
- resorption
- prevention of cementum formation
2) provide an epithelial lined pathway for eruption
3) forms initial junction epithelium

Question 14

Answer 14

Question 15

Answer 15