1. Fluorides and their role in clinical dentistry

2. Clinical context
The parent of your 9 year old patient has been reading in the paper about the benefits of fluoride and is curious to find out from you, what fluoride is and how does it work to protect teeth against decay ?

3. Objectives Understand the place of fluorides in the
prevention & treatment of dental caries.
Mechanism of Absorption & Metabolism .
Occurrence of Fluoride.
Fluoride Intake.
Mechanism of Action.
Sources of Fluoride used in Dentistry
   Systemic Fluorides
Topical Fluorides.
Dental Fluorosis and how to minimise fluorosis .
Recommendations regarding prescription.

4. Prevention of Dental caries
Factors which tip the balance towards
Remineralisation
1. Fluoride
2. Control of cariogenic foods & increase in caries
protective foods
3. Plaque control
4. Saliva stimulation – increasing salivary flow
(cleansing, flushing), increasing the pH (buffering).
Presence of high levels of calcium and phosphate ions.
5. Fissure sealants

5. F is normal constituent of the human body regardless of daily intake
The major amount of fluoride absorbed each day is derived from drinking water
97% of soluble fluorides in drinking water is absorbed regardless of level present
F is normal constituent of the human body regardless of daily intake
blood plasma, saliva, soft tissues maintain a constant resting level 0.14ppm- 0.19ppm

6. Sources of fluoride 1. SYSTEMIC FLUORIDE SOURCES –SWALLOW/DRINK/EAT
Drinking water.
Food - fish, chicken bones, processed foods using fluoridated water, infant formulas.
Beverages eg: tea, soft drinks (using fluoridated water), bottled water.
Dietary supplements eg. fluoride tablets, fluoride drops.

7. Sources of fluoride
2. TOPICAL FLUORIDE SOURCES – APPLIED DIRECTLY/LOCALLY TO SURFACE OF TOOTH
Fluoridated Toothpaste
Fluoride self applied or professionally applied
gels, mouth rinses, varnishes, foams.
Pre 1960s – sources of F from drinking water and food containing natural amounts of F
After 1960s – adjusted F levels in public water supply to a level required for optimal
prevention of dental caries
Use of F tthpastes and supplemental F eg.tablets
1980’s - intro of F sources such as self applied or professionally applied gels,
mouthrinses, varnishes
Distinction between systemic and topical sources of F not that clear cut.

8. Mechanisms of action of fluorides – General principles
There are 2 Anti-caries mechanisms of
fluoride:
PRE-ERUPTIVE
POST-ERUPTIVE

9. Pre-eruptive mechanism
F is ingested (drinking F water, F tablets, F drops, and accidentally swallowing F toothpaste )
& incorporated into the enamel during its formation (unerupted teeth).
Results in the formation of Fluorapatite (FA)
FA critical pH for dissolution = 4.5 compared with 5.5 for HA.
2F- + Ca 10 (PO4)6 OH 2 = Ca 10 (PO4)6 F OH –
Research ---- Approx 10% of apatite in enamel and dentine = FA therefore offering 60% of protection against demineralisation in children

10. Pre-eruptive mechanism
As fluoride is incorporated in the developing enamel to form Fluorapatite – it increases resistance to demineralisation and thus prevent caries.
Benefits children.
(approx 10% of apatite in enamel or dentine = FA) – this offers 60% protection against demineralisation in children

11. Post-eruptive mechanism
Fluoride from topical sources (F toothpastes /gels/mouthrinses) or from drinking water which after ingestion remains in saliva/plaque or recirculates in saliva)
Fluoride acts directly on the surface of the tooth (plaque/tooth surface interface)
after the tooth has erupted - during maturation phase
&
during demineralisation.

12. Post-eruptive mechanism
Results in 4 main effects:
Enhancement of remineralisation
Lowering of critical pH for demineralisation of enamel
Inhibition of bacterial growth and metabolism
Inhibition of acid formation

13. REVIEW:
Fluoride has a role in the prevention of caries and treatment of caries.
2. Systemic & topical fluoride sources
can iinhibit caries & enhance remineralisation
Via both pre and post –eruptive mechanisms
Eg:
Water – drink it – systemic source of F but acts both via pre and post eruptive mechanisms.
– stays in saliva/plaque adj to tooth and acts on erupted tooth surface
- when swallowed, can be incorporated into developing enamel in a child. –pre-eruptive mechanism
- when swallowed the fluoride also gets into the body fluids eg: saliva and then can have a post - eruptive effect on surface of tooth.
Toothpaste – topical F source apply it to teeth direct but acts both via pre and post eruptive mechanisms
– stays in saliva/plaque adj to tooth and acts on erupted tooth surface – post eruptive effect.
- when swallowed the fluoride can get incorporated into developing enamel in child – pre-eruptive effect
- when swallowed the fluoride also gets into the body fluids eg: saliva and then can have a post - eruptive effect on surface of tooth

14. Fluorides in oral fluids
Saliva
v low levels 0.019ppm
But play important role in remineralisation.
Plaque
level of F in plaque is x saliva.
F in plaque is held in compounds which are in dynamic equilibrium with plaque fluids. It is released under mild acidic conditions ie: pH drops after bacterial acid formation.
Fluoride in saliva
- v low levels 0.019ppm.
- has been shown that F is present in saliva and that elevated levels of salivary F are important in the prevention of caries – especially by assisting in remineralisation of lesions.
- Amount of F from topical agents eg: toothpaste that remains in the saliva depends on how fast it is cleared from oral fluids. – If some is swallowed it will reappear in the saliva.
Fluorides in dental plaque
- Dental plaque accumulates F by taking it up from saliva and gingival crevicular fluid. Mechanism of accumulation is not clear. It is believed that microcrystals of CaF2 or FA may be present in the plaque.
- the level of F in plaque is times greater in saliva ie. 5-10ppm
- F agents have minimal influence on the concentration of F delivered to the plaque fluid and the availability of saliva to remove it.
- Within plaque F is found in 3 different forms
Free fluoride (ionic fluoride) – in plasma water
Loosely bound –Is present as insoluble calcium salts. These F salts can be released by acidification to pH 4-5.
Tightly bound – taken up by plaque bacteria
In plaque not much of the F is in the free ionic level but bound (thus not available to the cariogenic bacteria).
- F levels found in plaque can affect the cariogenic bacteria
if high can kill sensitive bacteria and may reduce the tolerance of S mutans to acidic conditions
if low can alter bacterial CHO metabolism IPS and EPS and thus acid production and slow the pH drop after person consumes dietary simple CHO’s.
Hence – implications for prophylaxis prior to a topical F
Ie: don’t need to remove plaque before doing a topical F treatment.

15. In Summary
Fluoride works to control early dental caries in several ways. Fluoride concentrated in plaque and saliva inhibits the demineralization of sound enamel and enhances the remineralization (i.e., recovery) of demineralized enamel (As cariogenic bacteria metabolize carbohydrates and produce acid, fluoride is released from dental plaque in response to lowered pH at the tooth-plaque interface.

16. Summary
The released fluoride and the fluoride present in saliva are then taken up, along with calcium and phosphate, by de-mineralized enamel to establish an improved enamel crystal structure. This improved structure is more acid resistant and contains more fluoride and less carbonate Fluoride is more readily taken up by demineralized enamel than by sound enamel. Cycles of demineralization and remineralization continue throughout the lifetime of the tooth.