amelogenesis Flashcards
describe enamel
- mineralised epithelial product
- 96% mineral - hydroxyapatite
- 1-2% organic matrix
- enamel proteins
- NOT collagen etc
- 2% water
- starts to form after dentine mineralises
describe enamel spindle formation
nucleus of ameloblast polarises, goes to one size odontoblast process may enter enamel epithelium
describe enamel prisms
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
what is the final cue for onset for amelogenesis?
- dentine formation
- breakdown of basal lamina
Ameloblast
- secretes organic matrix
- immediate partial mineralisation
amelogenesis maturation by?
- influx of mineral ions
- breakdown and removal of most of the organic matrix
describe enamel matrix (an epithelial product)
organic matrix: amorphous gel
enamel proteins:
- amelogenins (90%)
- enamelins - (~2%) strongly binds to mineral
- tuftelin - confined to ADJ
- enzymes
describe amelogenins
- Rich in proline and glutamine
- similar in different species - clinically useful
- hydrophobic - aggregate
- spread throughout the developing enamel thickness
- thixotropic
what is the role of enamel proteins?
- aid nucleation of hydroxyapatite
epitactic matrix - orientate + stabilise crystal growth
- broken down and lost during maturation
what is enamelins?
- the matrix that flows out - amelogenins
- the matrix that remains - enamelin
describe enamel cuticle
- formed when maturation is complete
- final ameloblast secretion - the enamel cuticle
describe reduced enamel epithelium
- forms when enamel formation is complete
derived from: - reduced ameloblasts
- other remmants of the enamel organ OEE etc
- attached to the cuticle
what is the function of the reduced enamel epithelium ?
1) protection of enamel surface from:
- resorption
- prevention of cementum formation
2) provide an epithelial lined pathway for eruption
3) forms initial junction epithelium