(2) Anatomy and Histology of the Periodontium - Enamel (A) Flashcards
Where is enamel thick and thin on a tooth?
Thickness varies from up to 2.5mm (1.3mm in primary) over cusps to feather edge at cervical margins.
occlusal surfaces on cusp tips
What structures of a tooth can regrow?
dentin and cementum
What provides the support to enamel?
dentin - resilient
Does enamel have a high or low tensile strength?
low - brittle
Where is the hardest enamel found?
Surface enamel is harder, denser and less porous than subsurface enamel.
What layer of enamel is most mineralised?
the surface
What is the gradient of hardness and density in the
Hardness and density decrease from the cusp tips to the cervical margins.
What colour is young enamel vs old enamel?
Young enamel appears white turning to a more yellow appearance as translucency increases with age.
What is the percentage breakdown of enamel?
Enamel is composed of 96% inorganic components, 2% organic component and 2% water by weight.
What is the principal mineral component of enamel?
calcium hydroxypapatite
What are examples of organic substances in enamel?
50-90%
Free amino acids, small molecules, peptides and large protein complexes (amelogenins and non-amelogenins)
What shape do hydroxyapatite crystals form?
hexagonal
What do you call a crystal of hydroxyapatite?
crystallite
What are the dimensions of an enamel hydroxyapatite crystal?
Enamel hydroxyapatite crystals are about 70nm in width, 25nm thick and of great length (almost the full thickness of enamel).
What makes up each hydroxyapatite crystal unit?
One hydroxyl group surrounded by 3 calcium ions which are surrounded by 3 phosphate ions. Six calcium ions in a hexagon enclose the phosphate ions.