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
how much fluoride does normal toothpaste have
1350-1550ppm
how much fluoride does kids toothpaste have
at least 1000ppm
how much fluoride in drinking water
1ppm
how does glass ionomer cement act on fluoride
fluoride battery
takes up fluoride + release it again
can relate other ions like strontium
what can fluoride toxicity cause
fluorosis
complex formation
