Enamel Flashcards
What is enamels composition?
Almost entirely mineral by weight
95% is inorganic hydroxyapatite crystals
Remainder - enamel proteins, water and lipid material
Organic matrix (1-3%) of enamel may contribute to fracture toughness of enamel
What are the physical properties of enamel?
Can undergo neither repair nor replacement
High modulus of elasticity and with flexibility of underlying dentine minimises possibility of fracture
What origin does enamel have?
Ectodermal, and originates from the IEE of the tooth germ
Which proteins are selectively reabsorbed during enamel maturation?
Amelogenins
What four proteins comprise the organic matrix of enamel/
Amelogenin, ameloblastin, tuftelin and enamelin
What does amelogenin do?
Stabilises CA-P phase, controls crystal morphology and organisation
What does ameloblastin do?
Cell adhesion protein, controls cell differentiation and maintains enamel rod/prism integrity
What does enamelin do?
Controls mineral nucleation and elongated growth
What does tuftelin do?
Cell signalling
Which part of the Tomes process creates rods?
Distal
Which part of the Tomes process creates inter rods?
Proximal
What causes prism boundaries?
Seen due to sudden changes in crystallite orientation between the prism core (head) and tail of adjacent prisms
What are hunter-schreger bands?
Periodic changes in prism direction in alternating sheets of enamel (ones that do not follow the usual sinusoidal direction from the EDJ towards the surface.
Why do the arrangement of crystallites and prisms impart strength and resistance to fracture?
Prisms travelling in different directions in sheets, and prisms are in staggered rows such that there is interlocking and offsetting of prism heads and tails of adjacent rows
What are Striae of Retzius?
Prominent lines that run obliquely across enamel prisms to the surface, reach surface at perikymata
