Introduction to Fluoride Flashcards
What is dental caries caused by?
- interaction of carcinogenic bacteria with carbohydrates on the tooth surface
- carcinogenic bacteria metabolise carbohydrates for energy and produce organic acids
- the acids lower the pH of the plaque biofilm
What is the hydroxyapatite of tooth enamel composed by?
- phosphate ions
- calcium ions
What is the critical pH level in enamel and dentine?
enamel = 5.5
dentine = 6.5
What happens once the pH drops below the critical level?
- causes the dissolution of hydroxyapatite (tooth mineral)
- process is called demineralisation
When does remineralisation occur?
- when the buffer of saliva elevates pH
- minerals are reincorporated into the tooth
What is the primary mineral source of fluorine?
- fluroite
- fluropatite and cryolite also used
What foods are high in fluoride?
- fluoridated water
- tea
- grape juice
- chicken
- sardines
What did the original debate for how fluoride worked?
thought that fluoride had to be ingested and acts pre-eruptively
What has recent research concluded on fluoride?
- the caries-preventative effect of fluoride is almost exclusively post-eruptive
What supports the posteruptive fluoride effect theory?
- in vitro laboratory investigations
- demonstrating that the mode of action of fluoride can be attributed mainly to its influence of de and remineralisation kinetics of hard tissues
What is the primary mechanism of action of fluoride in preventing dental caries?
- Topical application
How does fluoride act to prevent dental caries?
- enhances remineralisation of the tooth enamel (most important effect)
- it inhibits demineralisation of the tooth enamel
- makes carcinogenic bacteria less able to produce acid from carbohydrates
What did early studies of water fluoridation show?
- the anterior teeth had a greater reduction in caries
- water being drunk came into contact with anterior teeth more often
- reducing caries in anterior teeth more then posterior teeth
What happens to the tooth in the presence of the fluoride ion?
- the OH- ion is replaced by the fluoride ion
- producing fluoropatite
How does producing fluorapatite help the tooth?
- it is more resistant to acid demineralisation than hydroxyapatite
- teeth developed in the presence of fluoride have more well coalesced grooves on the occlusal surfaces and fewer pits and fissures
When does the demineralisation of teeth occur?
- sugar enters the oral cavity
- bacteria on the surface of teeth form biofilm creating plaque
- bacteria covert sugar to acid
- causes pH in mouth to fall below 5.5
- hydroxyapatite begins to dissolve
What is fluorides critical pH?
4.5
How does fluoride work?
- F- binds to the remineralising surface of enamel
- induces the preferential formation of fluorapatite in place of hydroxyapatite
Fluoride working:
What do fluoride ions do in remineralisation?
- replaces the OH- groups in hydroxyapatite to make fluroapatite
- which rebuilds the surface of teeth
Remineralisation:
What happens when the tooth surface becomes acidic?
- phosphate in oral fluids combines with hydrogen H+ ions
- forming various hydrogen phosphate species
- causing phosphate to be pulled from tooth enamel
- restoring phosphate levels in the saliva and hydroxyapatite dissolves
- as pH returns to normal calcium and phosphate in saliva recrystallise
- into hydroxyapatite, remineralising the enamel
What is fluoride absorbed more readily by?
- Demineralised enamel than by sound enamel
What does dental plaque contain?
- 10 mg F/kg weight in low fluoride regions and approx
- 20 mg F/kg in fluoridated communities
