Enamel Morphology Flashcards
Describe enamel (8)
Hardest tissue in the body Resists abrasion Brittle Supported by dentine Covers tooth crown Varies in thickness Translucent Transparency increases with mineralisation
Describe the regional variants of enamel
Surface enamel is more mineralised and harder than deeper enamel
Hardness decreases from cusp tip/incisal edge to cervical region
Describe an enamel rod (prism)
5um x 2.5mm
Run from ADJ to surface
Rods contain >10^6 crystallites
What gives enamel rods their structure
The orientation of crystallites
What is the enamel content
Hydroxyapatite - 95% weight, 90% volume
Water - 4% weight, 5-10% volume
Organic matrix - 1% weight, 1-2% volume - made of proteins: amelogenins, enamelins, peptides and amino acids
Describe HA crystallites
Hexagonal crystals
70nm x 25nm x 1um
Which ions commonly substitute HA crystals
Mg2+
(CO3)2-
F-
Describe the histological features of enamel
Ground sections - mineral present, no soft tissue
Decalcified sections - no mineral, only soft tissue
Describe the directions of enamel rods
Run in a sinusoidal course
Adjacent rods have different orientations
This causes bonding patterns (Hunter-Schreger bonds)
What are common optical features of enamel
Hunter-Schreger bonds
Gnarled enamel
Incremental lines
Give examples of incremental lines found in enamel
Brown striae of Retzius
Perikymata
Neonatal line
What are enamel tufts
Hypomineralised regions due to residual matrix protein at prism boundaries
What are enamel lamella
Incomplete maturation of groups of prisms extending through enamel thickness
What are enamel spindles
Odontoblast processes extending into dentine
