Flashcards in Biomineralization Deck (94)
What percent of enamel is mineral?
What percent of dentine is enamel?
What is the purpose of organic components in mineralized tissues?
To provide scaffold and regulate process
What are the three organic components in mineralized tissues?
What is the mineral phase in mineralized tissues?
What is enamel lacking that most other mineralized tissues have?
In hydroxyapatite, apatite is based on what, rather than composition?
Structure, not composition
Is hydroxyapatite (HAP) a pure chemical compound?
What is a unit cell?
A conceptual entity representing the smallest section of a crystal
How many possible unit cells are there?
What is the lattice in crystals?
The pattern of repetition of the unit cells in a crystal
To which system of crystal structure do apatites belong?
What shape do naturally occurring hydroxyapaties form?
Hexagonal prisms and plate-like crystals
What is the shape of the hydroxyapatite lattice?
Triangular groups of 3 Ca located along c axis with each triangle rotated 60 degrees relative to the next layer
Where is the OH group found in a hydroxyapatite lattice?
In the center of the triangle, slightly above/below the plane
Why can't two OH groups be oriented toward each other in hydroxyapatite lattices?
What lies around each crystallite?
A hydration shell
What are the measurements of crystals in mesenchymal hard tissues?
150-400 angstroms long
50-100 angstroms wide
25-50 angstroms thick
What are the measurements of crystals in enamel?
1400 angstroms long
500-800 angstroms wide
250-300 angstroms thick
The small size of crystals in bond and dentin mean what?
They have enormous surface area
Biological apatites are ___ apatites.
In hydroxyapatite crystals, Ca can be substituted for what ions?
In hydroxyapatite crystals, PO4 can be substituted for what ions?
In hydroxyapatite crystals, OH can be substituted for what ions?
Apatites of normal bone, enamel and dentin are principally what type of apatites?
Type B carbonate apatites
Where do ions get absorbed or bound into the apatite crystal?
In the hydration layer
3-6% of phosphate groups in bones and teeth are replaced by what groups?
Substituting carbonate groups instead of phosphate groups in the hydroxyapatite crystals has what effects?
More susceptible to acid dissolution
What part of the teeth has the least amount of carbonate, Mg and Na