Lecture 4 - Fluoride and dental caries Flashcards
(41 cards)
T/F there is a benefit from fluoridate water before tooth eruption. To continue benefits, fluoridation must continue throughout life/
F - no benefit before tooth eruption
T
T/F fluorosis risk is decreased by ingestion
F - increased
What is enamel laid down by?
ameloblasts
what happens during the secretory stage of enamel formation?
ameloblasts lay down protein matrix for rod crystal structure. rod formation begins
what happens during maturation stage of enamel formation?
ameloblasts fill in crystal structure with mineral
very high physiologic levels of fluoride during secretory stage can cause:
pitting and disturbances
high levels of fluoride during maturation stage cause disruptions in crystal formation appearing as:
chalky whiteness and weakness of enamel
T/F after eruption, weakened enamel may fracture and stain. A lot of fluoride is incorporated into enamel during pre-eruptive maturation process
T
F - little fluoride
What is the composition of enamel?
87% hydroxyapatite
11% water
2% organic matrix
impurities found in newly formed crystals in a young tooth are usually:
carbonate
sodium
other ions
process where phosphate replaces carbonate, calcium replaces sodium and fluoride replaces hydroxyl is known as:
post-eruptive enamel maturation
T/F
young teeth are less susceptible to caries
enamel maturation strengthens them over time
F - more susceptible
T
At what pH does hydroxyapatite dissolve?
if pH is below 5.5
fluorhydroxyapatite forms on surface when hydroxyapaite dissolves from subsurface at what pH when fluoride ions are available?
above 4.5
at what pH do fluoride ions enhance remineralization of enamel and dentin?
above 5.5
T/F presence of fluoride at low levels in solution is more beneficial than high concentrations incorporated into enamel
T
T/F
surface has more fluoride and less carbonate
outer enamel is more soluble than interior
T
F - less soluble
why do whitespot lesions have very high fluoride concentrations on their surface?
demin-remin cycles
T/F areas covered by plaque have lower fluoride levels
worn areas contain low levels of fluoride
F - higher
T
T/F when topical fluoride concentrations are low (50 ppm or less), fluorhydroxyapatite is formed on outermost layers of enamel
T
when topical fluoride concentrations are above 100 ppm what precipitates?
calcium fluoride
calcium fluoride is increased by: 1 2 3 4
1 increasing fluoride concentration (10000 ppm)
2 increasing exposure time (4 min)
3 lowering pH
4 protection - using rinsing or varnish
T/F teeth dissolve when saliva is supersaturated with calcium and phosphate
F - teeth don’t dissolve
T/F
plaque prevents access of saliva to enamel surface
in plaque biofilm, interbacterial fluid cannot have higher concentrations of calcium and phosphate leading to calculus formation
T
F - they can have higher concentrations
