Lecture 4: Fluoride and dental caries Flashcards
what is the ideal concentration of fluoride to minimize fluorosis?
1 ppm
T/F there is no benefit from fluoridated water before tooth eruption
true
what type of cells create/lay down enamel?
ameloblasts
during the _____ stage, ameloblasts lay down protein matrix
secretory
during the _____ stage, ameloblasts fill crystal structure with minerals
maturation
high levels of F during the secretory stage causes
- pitting
- disturbances in form
moderately high levels of F in the maturation phase causes
- disruptions crystal formation
- chalky whiteness
- weakness of enamel
- enamel may fracture or stain
T/F little fluoride is incorporated into enamel during the pre-eruptive maturation process
true
what is the enamel composition
- 87% mineral (hydroxyapetite)
- 11% water
- 2% organic matrix
formula for hydroxyapetite
Ca-10, PO4-6, OH-2
what are some impurities in young tooth
- carbonate
- sodium
- other ions
what are some of the replacements caused by post-eruptive enamel matruation
- phosphate replaces carbonate
- calcium replaces sodium
- fluoride replaces hydroxyl
Hydroxyapatite dissolves if pH drops below _____
5.5
T/F acid continues to dissolve because H+ combines with PO4 and OH ions, le chatlier
true
if the pH remains above _____, flurohydroxyapatite forms on the surface when hydroxyapatite dissolves in the subsurface
4.5
T/F when pH raises above 5, F ions enhance remineralization of enamel and dentin
false, 5.5
T/F presence fo F at low levels in solution is more beneficial than high concentrations incorporated into enamel
true
T/F surface has more fluroride and less carbonate
true
T/F outer enamel is more soluble than interior
false
Areas covered by _____ have higher F levels
plaque
when topical fluoride concentrations are ____, fluorhydroxyapatite is formed on the outermost layer of enamel
50 ppm
when topical fluoride concentrations are _____, calcium fluoride precipitates
100 ppm
T/F calcium fluoride provides temporary storage of F that is gradually dissolved
true
CaF2 deposition is increased by
- increasing concentration of F
- increasing exposure time
- lowering pH
- protecting with limited rinsing or cover
crystals do not grow due to _____ that coat the enamel surface
- salivary pellicle proteins
- tyrosine rich peptides, statherin, proline-rich proteins
T/F fluorosis can only occur when teeth are developing
true
T/F exposure to F during development is a major determinant of F levels in enamel
false
fluorosis severity and incidence correlated with _____
amount of exposure
what teeth are at greatest risk for fluorosis?
central incisors
F- binds to sites that would normally bind ____ and inhibits enzymes and regulatory proteins
OH
T/F bacteria can develop resistance to F
false
what enzyme does F inhibit to stop the production of lactase?
enolase
T/F fluoride reduces that enrichment of acid-tolerant species
true
Optimum benefit of fluoride presence during _____ challenge
acid
concentration of toothpaste in US
1000 ppm F
3 types of fluoridated toothpaste available
- NaF2
- monofluorophosphate (MPF)
- SnF2 (stannous fluoride)
what concentration of toothpaste is available for Rx?
5000 ppm
T/F there is a direct relationship between the amount of toothpaste and caries
false
concentration of fluoride rinses
200 ppm, 25% reduction in caries
composition of professional fluoridation
1.23% acidulated phosphate fluoride
most effective professional product
- fluoride varnish
- 2.2% F as NaF
- 40% reduction in caries
T/F water fluoridation deposits CaF2 on the surface of the tooth
false
T/F ingestion of fluoride carries risk of fluorosis
true
