fluoride Flashcards
why is fluorapaetite better than hydroxyapatite
chemically + thermodynamically more stable
more resistant to acid attack
less likely demineralise
what is apatite also called
calcium phosphate
what can replace the calcium and phosphate in apatite
strontium replace Ca – more resistant to acid
Mg + manganese for calcium
carbonate for phosphate
draw the diagram of apatite crystal structure
in book
hexagon with star in middle
describe positions of 2 calcium in apatite structure
calcium II closer to fluoride
calcium I further away
how does size of OH disrupt apatite structure
OH too big for ideal hexagons lattice
it displaces above Ca triangle
destabilises crystal structure
distorted hexagon/monoclinic structure
why does Fl and strontium fit better into site
slightly smaller
why is it good Fl + strontium fit better into site
Fl- ions easily exchanged for OH- in enamel surface
crystal is hexagonal
Fluoroapatite chemically + thermodynamical more stable than hydroxyapatite so more resistant to dissolution in acid
how are ions held together in apatite
h bonding
what is formula of hydroxyapatite
Ca10(PO4)6(OH)2
what are characteristics of enamel apatite
contains more fluoride –> more ordered crystal structure
gives sharp diffraction lines
what is the apatite equilibrium
look at written
how is tooth decay formed
bacteria in plaque + caries lesions
bacteria ferment starch + make acid -> demineralisation
produces enzymes - hydrolyse teeth proteins
is enamel or dentine more resistant to acid attack
enamel
how does acid erosion occur
acids from fruit juices + carbonated drinks
demineralisation
