Introduction:

Occurrence in nature: Widely distributed in the earth’s crust, 17th most

abundant(0.06 to 0.09%)

Reactivity: It is the most electronegative of all the elements, which makes it

extremely reactive. It combines with almost every element and also reacts

with organic radicals. It is rarely found in the free state in nature.

Form of occurrence: Fluorine occurs as minerals as fluorspar(CaF2),

cryolite(Na3AlF6) or fluorosilicates(Na2SiF6).

In biological mineralized tissue, such as bones and teeth, it occurs as

fluoridated hydroxyapatite(Ca10(PO4)(OH)2-X FX), where X is much smaller

than 2.

So, only some of the hydroxyls of the apatite lattice are replaced by fluoride

ions, yet this change profoundly alters the resistance of enamel to

demineralization.

Sources of fluoride: Water, Drinks(carbonated beverages, fruit juices), Tea

leaves, Cereals, Meat, Fish, Infant formula

Infant formula:

o Variable amounts of fluoride, the amount depending primarily on

fluoride content of water used as diluent.

o It has been shown that fluoride intake during infancy may be an over-

riding factor in the development of enamel fluorosis of the permanent

teeth.

Fluoride metabolism:

F- in diet/supplements F- from inhalation F- from metabolism

of GA agents

Absorption in GIT

Fluoride in plasma

Mineralized tissues Soft tissues Excretion in

urine(50% of ingested dose)

Fluoride source may be inorganic or organic. Depending upon the physical and

chemical properties of compound and its solubility, varying amounts of ingested

fluoride dose will be absorbed and enter the systemic circulation.

NaF is rapidly and almost completely absorbed. There is detectable rise in the

plasma F- conc. only a few minutes after the dose is swallowed.

CaF2, MgF2 and AlF3 are less completely absorbed.

The plasma peak usually occurs within 30 min(independent of amount of F-

ingested) , if dentifrice is ingested on a fasting stomach. But when the dentifrice is

swallowed 15mins after a meal, the peak does not occur until after 1 hour.

The height of plasma peak is proportional to –

-Fluoride ingested (directly proportional )

-Rate of absorption (directly proportional )

-Body weight of the subject (indirectly proportional )

Ingestion of fluoride with food retards its absorption. On a fasting stomach, degree

of absorption of NaF is almost 100%. If taken with milk, it decreases to 70%.

Absorption is only 60%, when F- is taken with calcium rich breakfast.(Reason---F-

binds with Ca++ and other food constituents and so fecal excretion of F-

increases).

Clinical significance: If toothbrushing occurs soon after a meal, F- absorption will

be inhibited to some extent, and high plasma F- peaks will not occur. This might be

important for small children, who tend to retain and ingest more of toothpaste

applied to the brush.

(a thorough rinsing after toothbrushing will minimize the ingestion of F- following

toothbrushing with fluoridated toothpaste.)

Absorption of fluoride

By passive diffusion

From both stomach and intestine

Rate of absorption is related to gastric acidity.

F- in diet

HF is formed in stomach

Readily passes through biologic membranes

Fluoride in plasma

2 forms:

o Ionic/free/inorganic

o Non-ionic/bound

Fluoride levels in plasma are not homeostatically regulated but instead they

rise and fall according to the pattern of fluoride intake. So, there is no

‘normal’ physiologic concentration.

The plasma fluoride level in a healthy, fasting, long term resident of a

community with water fluoridation(1ppm) is approx 1µM(0.019ppm)

Diurnal changes in levels in subjects living in an area with a high fluoride

conc. in drinking water particularly in adults.

Pharmacokinetics of fluoride

After single fluoride dose, the pharmacokinetic analysis shows 3 phases

i. Initial increase(represents mainly absorption): upto 1 hr

ii. Rapid fall/ α phase(represents mainly distribution to soft tissues and bone

initially and then followed by resting skeletal muscle and adipose tissue): for

about 1 hr

iii. Slower decline/ β phase(represents elimination)

The plasma half-life for fluoride in human adults typically ranges from 4 to10 hrs.

Higher the plasma concentration of fluoride, faster the elimination.

Distribution:

Distribution in soft tissues:

More rapid in highly perfused tissues such as heart,lungs liver than for less

perfused tissues as resting skeletal muscle, skin and adipose tissues

Kidney tubules have higher conc of F- than that of plasma.

Blood brain barrier is effective in restricting passage of F- into CNS(which

has only 20% that of plasma).

Distribution in mineralized tissues:

Approx. 99% of all fluoride in human body is found in mineralized tissues.

The apatite has capacity to bind and integrate fluoride ion into its crystal

lattice

The selective affinity of fluoride for mineralized tissues is, in short term, due

to uptake on the surface of bone crystallites by the processes of isoionic and

heteroionic exchange. In the long term, it is actually incorporated into the

crystal lattice structure in the form of fluorapatite or fluorhydroxyapatite.

During the growth phase of skeleton, a relatively high portion of an ingested

fluoride dose will be deposited in skeleton( more as compared to an adult).

Fluoride is not irreversibly bound to bone. So, the fluoride is mobilized from

bone to plasma when person moves from highly fluoridated area to low

water fluoride level area.

Distribution to the fetus:

The placenta is not a barrier to pssage of fluoride to fetus.

There is direct relationship between the serum fluoride concentrations of

mother and fetus.

From the fetal blood, fluoride is readily taken by mineralizing fetal bones

and teeth.

Excretion

Major route- via Kidneys. Renal clearance of fluoride dependent on GFR

rate(more GFR, more fluoride excretion), urinary pH(As the tubular fluid

becomes more acidic, more of ionic fluoride is converted into HF which gets

diffused out of tubules ).

Other routes- breast milk(limited transfer), feces(10% of ingested

dose),sweat.

Fluoride in teeth and bone

Approx. 99% of all fluoride in human body is found in mineralized tissues.

The apatite has capacity to bind and integrate fluoride ion into its crystal

lattice

The selective affinity of fluoride for mineralized tissues is, in short term, due

to uptake on the surface of bone crystallites by the processes of isoionic and

heteroionic exchange. In the long term, it is actually incorporated into the

crystal lattice structure in the form of fluorapatite or fluorhydroxyapatite.

During the growth phase of skeleton, a relatively high portion of an ingested

fluoride dose will be deposited in skeleton( more as compared to an adult).

Fluoride is not irreversibly bound to bone. So, the fluoride is mobilized from

bone to plasma when person moves from highly fluoridated area to low

water fluoride level area.

Concentrations in mineralized tissues are variable due to

o Level of fluoride intake

o Duration of exposure

o Factors as stage of tissue development, its rate of growth, vascularity,

surface area and reactivity of mineral crystallites, porosity and degree

of mineralization.

In all mineralized tissues, fluoride levels tend to be greatest at surface since

this region is the closest to tissue fluid supplying fluoride.

The distribution and concentration in surfaces changes differentially with

age.

Mechanism of fluoride uptake

o Body fluoride mainly as inorganic fluoride, although F- binding to

organic components is possible.

o As pKa of HF is 3.4, fluoride in blood,saliva and tissue fluid will be

present in fully ionized form as F-. However, fluoride at low pH eg. In

the stomach(pH of approx.2) will exist almost totally in undissociated

form ie. HF.

o Fluoride

Superficially adsorbed on crystal surfaces or loosely entrapped

in hydration shells of mineral crystallites

Incorporated into interior of mineral crystallites

o When fluoride is applied to a tooth surface in a highly concentrated

form(often at low pH), dissolution of apatite mineral.

Phosphate(PO43-) and hydroxyl (OH-) from tooth mineral will enter solution

F- replaces OH- ion F- replaces CO32- ion F- together with CO3

2- may replace PO43-

Most of fluoride within mineral crystallites is acquired during the period of crystal

growth, a process known as ‘ accretion’. But even during periods of active crystal

growth, acquisition of fluoride by exchange or absorption will also be important.

Fluoride loss from bones and teeth:

Loosely and even some of firmly bound fluoride may be lost as crystals are

destroyed.

Action of fluoride

Action of fluoride depends on the conditions of its use. Professional fluoride ie

high fluoride conc. affects (at least temporarily)bacterial metabolism,inhibiting

glycolysis and suppressing Streptococcus mutans. At low conc. eg systemic

fluoride provided by water fluoridation or supplements or topical fluoride from

dentifrices and mouthrinses, there is an uptake of fluoride by hydroxyapatite,

rendering it less soluble and improving its crystallinity. Fluoride also promotes and

accelerates remineralization of calcium-depleted tooth structure.

Hypotheses regarding fluoride’s anticaries mechanism of action

1. Action on the hydroxyapatite of enamel

a) Decresing its solubility

b) Improving its crystallinity

c) Remineralizing calcium-depleted mineral

2. Action on bacteria of dental plaque

a) Inhibiting enzymes

b) Suppressing cariogenic flora

3. Action on the enamel surface

a) Desorbing proteins and/or bacteria

b) Lowering the free surface energy

4. Alteration of tooth morphology

Alteration of tooth morphology:

Researcher Finding

Forrest (1956) and

Ockere(1949)

Commented on ‘well rounded cusps and shallow fissures’of

teeth from fluoridated areas in Great Britain and South

Africa, but presented no statistical data.

Wallenius(1959) Reported that children on water containing 0.5-1.0ppm F

were 1.7% wider than those receiving <0.5ppm F, using

plaster casts of teeth from 419 children. The difference was

more significant in mandibular teeth in boys.

Simpson and

Castaldi(1969)

Reported that teeth in fluoride area were larger than in low-

fluoride control area and had shallower fissures(more

significant difference in mandibular molars) and obtuse

inter-cuspal angels.

The results on tooth size are contradictory. There is a consensus that occlusal

surfaces are more rounded under the influence of fluoride, but the effect is

generally considered to be too small to be of much practical importance.

Possible mechanism of morphological effects of fluoride:

Depending upon the experiments by Kruger(1968), it is suggested that fluoride

changes the ultrastructure of ameloblats. Large vacuoles appear in RER (organelle

associated with protein synthesis). This change is suggested to affect the synthesis

of protein and this reduction in amount of matrix protein further reduces the

thickness of enamel and thus change in shape of fissure. In 1970, Kruger showed

the reduced uptake of proline by ameloblasts.

Effect of fluoride on crystallinity and reactivity of mineral:

Fluoride in interior of crystal lattice:

The incorporation of fluoride can significantly alter the properties of mineralized

tissues since the inclusion of any extraneous element in a crystalline lattice will

alters its reactivity. When F- replaces OH- ion in lattice, it can greatly increase

lattice stability, presumably by attracting the protons of adjacent apatite hydroxyl

ions thereby increasing degree of hydrogen bonding in so called ‘ hydroxyl

column’.

In addition, compared with hydroxyl , fluoride ion is better aligned within the

plane formed by calcium ions and there is more electrostatic attraction between

calcium ions and F- ions as compared to Ca2+ with OH-. So, the fluoridated apatite

lattices are more crystalline, more stable and therefore less soluble in acid.

Superficially located fluoride:

Superficially located may have relatively little effect on behavior of crystallite

lattice. It can affect fluid- crystal equilibria which involves interaction between the

ions at crystal surfaces and those in solutions.

Studies on solubility hypothesis:

Volker, 1939 Rate of dissolution of powdered enamel decreases if

it was exposed to fluoride solution prior to action of

acidic buffers on powdered enamel.

It was suggested that fluoride is producing crystal

with apatite which is less soluble

Issac et al,1958 Reported that 2 enamel layers with fluoride

containing 460 ppm and 1080 ppm differed in

solubility by only 1.9%

Mechanism of topical fluorides by action on demineralization/remineralization:

Enhancement of remineralization

Inhibition of demineralization

The plaque fluid containing plaque bacteria is in contact with enamel surface and

saliva/GCF. Plaque fluid transports organic acids as well as fluoride, calcium,

phosphate and other ions to enamel surface. The balance between these

factors(fluoride and pH being most important) determines demineralization or

remineralization of the tooth.

Dental plaque is normally richer in fluoride than the fluids to which it is exposed.

Plaque appears to be able to retain and concentrate fluoride.

Fluoride in saliva:

The conc of salivary fluoride from major salivary glands is about 2/3 of the

plasma fluoride concentration and seems to be independent of flow rate

The conc of fluoride in whole saliva is related to

o Dietary fluid intake

o Dental fluoride preparations

The salivary fluoride levels depend upon the fluoride levels in water levels.

Acc to a study by Oliveby A(1990), the children living in high fluoride

areas(1.2ppm )had higher F levels in saliva(0.9µM/L) as compared to low

fluoride areas(0.1ppm fluoride in water and 0.3 µM/L ). A diurnal variation

in salivary fluoride conc was also seen in high fluoridated area.

The ductal saliva is normally not an important source of fluoride in plaque or

plaque fluid. Following topical application of fluoride in the form of

mouthrinses, toothpaste or any other fluoride vehicles, there is 100- or even

1000- fold increase in salivary fluoride concentration of fluoride agent. This

high conc of F in saliva falls rapidly. Depending on the conc and type of

fluoride agent, the saliva F conc is reduced to a few ppm within an hour, and

within the next 3-6 hrs, returns to the baseline level.

Clearance of salivary fluoride varies considerably because of large variations

in

o Salivary flow rates

o Volume of fluoride distribution in oral cavity

o Individual variation in anatomy and the number of teeth

Fluoride from saliva to plaque:

Transfer of F from saliva to plaque may occur during or immediately after

mouthrinsing(0r similar procedures): a 10 mL volume of rinsing solution is

diluted in only 1-2 mL of saliva, giving a high salivary fluoride

concentration. When the mouthrinse is spat out, both the volume of fluid in

the mouth and conc of fluoride decrease, and salva becomes less important

as a source of plaque fluoride.

Fluoride in plaque:

o Exists in ionic and bound forms

o Sources of plaque fluoride: diet, saliva and crevicular fluid.

o 5-10ppm F wet weight in dental plaque

o Due to slower elimination of ion from the plaque and also due to

release of F from CaF2 present in plaque, the plaque F levels are

much higher than salivary F conc.

o Fluoride in plaque has a large variation at various sites in the mouth

eg maxillary incisor site has a much higher conc of fluoride than the

other sites.

o pH of plaque appears to be an important factor, low pH being

associated with low fluoride concentrations.

o Free form fluoride in plaque

Using mouthrinses/ dentifrices containing fluoride

Fluoride

Calcium in plaque becomes supersaturated

CaF2 formed

Ca+ + F-

Bacterial surfaces have a net negative charge due to abundant

phosphate and carboxyl groups. The acidic groups on the

surface of bacteria will acquire counterions, mainly

calcium(oral environment is rich in calcium). Fluoride can be

associated with calcium counterions. When pH approaches pK

of acidic groups, Ca+ and F- are released.

Fluoride in crevicular fluid:

o Low in fluoride

o F conc is closely related to plasma fluoride concentration

o Not an important source of fluoride for plaque

Fluoride and dental enamel

Large amounts of fluoride may be acquired by enamel as calcium fluoride

when exposed to fluoride toothpaste during tooth brushing, which is

subsequently covered by plaque. The pH changes in plaque covering this

fluoride rich enamel contributes to its rapid mobilization and transfer of

fluoride to plaque fluid. So, the CaF2 in outer enamel acts as reservoir and

releases Ca and F during caries challenges.

Enamel and dentin not covered by plaque may also take up fluoride, which

is slowly released.this source is probably less important than fluoride

deposited beneath plaque. Example is when paste is applied directly to tooth

enamel. This fluoride is replenished regularly and this reservoir is scarcely

depleted. This probably makes tooth-paste a particularly appropriate fluoride

vehicle.

Fluoride reservoirs in or on the oral soft tissue: F- is acquired during topical

application(although soft tissue fluoride is not a major source)

o This uptake is pH dependent, because fluoride penetrates more easily

as HF. HF is dissociated after the absorption and may not necessarily

be easily released.

o Some of fluoride in soft tissues is associated with calcium; pre-

treatment with calcium ions increases fluoride retention(calcium

attracted to acidic groups on the surfaces of the tissues, and retention

of fluoride is based on interaction with calcium counterions.

Connective tissue has sulfate- and carboxyl groups, whereas the

cellmembranes contain phosphate groups).

Professionally applied fluorides:

Accoring to AAPD, Professional topical fluoride treatments should be based on

caries-risk assessment. Children at moderate caries risk should receive a

professional fluoride treatment at least every 6 months; those with high caries

risk should receive greater frequency of professional fluoride applications (ie,

every 3-6 months). A pumice prophylaxis is not an essential prerequisite to this

treatment. Appropriate precautionary measures should be taken to prevent

swallowing of any professionally-applied topical fluoride.

Indications:

1) Caries-active individuals defined as those with past caries experience or

those who develop new carious lesions on smooth tooth surfaces

2) Children shortly after periods of tooth eruption, especially those who are

not caries-free.

3) Individuals who are on salivary flow-reducting medications, have

diseases that decrease salivary flow or have received radiation to head

and neck.

4) Patients after periodontal surgery, especially when the roots of teeth have

been exposed.

5) Patients with fixed or removable prostheses and after placement or

replacement of restorations.

6) Individuals with an eating disorder or who are undergoing a change in

lifestyle which may affect eating and oral hygiene habits conducive to

good oral health.

7) Mentally and physically challenged individuals.

Precautions:

Topical fluoride agents contain relatively higher concentrations of

fluoride, certain precautions need to be taken to prevent the patient from

inadvertently ingesting these agents.

If solutions are used, the teeth should be carefully isolated with cotton

rolls or gauze swabs and only enough solution applied to wet the surfaces

of the teeth and keep them wet.

If gels are to be used,

o Place patient in upright position

o Use minimal amount of gel(no more than 2.5ml per tray), sufficient to

cover the teeth but not to exude from the tray.

o Use custom-fitted or stock trays with absorptive liners

o Warn patient not to swallow gel

o Use suction, maintained during 4 minute application of agent.

o Remove excessive gel from teeth and gingival with gauze on removal

of the tray

o Instruct patient to expectorate thoroughly after treatment

Fluoride solutions

General features-

Characteristic NaF SnF2 APF

Fluoride(%age) 2% 8% 1.23%

Fluoride(ppm) 9,200 19,500 12,300

Frequency of

application

4 at weekly

intervals at ages

1 or 2/year 1 or 2/year

3,7,11 and 13

Stability Stable Unstable Stable in plastic

container

Taste Bland Disagreeable Acidic

Tooth pigmentation No Yes No

Gingival pigmentation No Occasional,

Transient

No

Effectiveness(average) 29% 32% 28%

Neutral sodium fluoride solution

In 1941, the first clinical study to use fluoride solution was done by Bibby

using 0.1% aqueous NaF solution.

After prophylaxis and drying of teeth, applications for 7-8 min were made 3

times a year at 3-4 monthly intervals. One year later, the caries increment in

experimental quadrant was 45% lower than that found in the opposing

control quadrant(Bibby 1943).

In 1942, Knutson used a different technique which required four visits

within a month.

After prophylaxis and drying, 2% aqueous NaF solution was applied for 3

min. Knutson concluded that maximum reduction in caries was achieved

from 4 treatments at weekly intervals and suggested that the series of

applications should be carried out at the ages of 3,7,10 and 13 years to

coincide the eruption of teeth(Knutson, 1948).this would minimize the

amount of time that teeth were at risk to caries attack before preventive

treatments were given.

This technique was recommended by USA Public Health Service(USPHS)

in public health programs

Although this regimen is not convenient for private practitioners who tend to

recall their patients for check-ups at 6-12 month intervals.

In 1948, Gagalan and Knutson showed that 1% NaF solution was equally

effective.

A number of studies using NaF solution reported reduction in caries.

In 1942,Knutson and Armstrong began a study involving children aged 7-15 years. The results

after 3 years are as follows:

quadrant No. of

caries-free

teeth(1942

)

New DF

teeth(1945

)

DF

surface

s in

new

DF

teeth

DF

surface

s in

previou

s DF

teeth

Total

new

DF

surface

s

Difference

in DF

surfaces(%

)

Treated 1870 214 287 216 503 32.8

Untreate

d

1888 338 464 284 748

Stannous fluoride solution:

General features:

o Both 8% and 10% sol of SnF2 have been tested, with little difference

observed in effectiveness.

o In 1962, Dudding and Muhler described a method for applying SnF2

solution to teeth.

Thorough prophylaxis

Teeth are kept wet for 4 mins, making the saliva ejector

essential

Treatments recommended at 6- month intervals

In vitro Studies:

Studied in/by Conclusion

Muhler and van

Huysen ,1947

Tin fluoride was the most effective fluoride salt in reducing

enamel solubility.

Muhler and

Day,1950

10ppm stannous fluoride in drinking water given to rats fed on

cariogenic diet was superior to 10ppm of sodium fluoride in

reducing caries

Muhler, Boyd and

van Huysen,1950

Stannous fluoride was 3 times more effective than sodium

fluoride in preventing dissolution of calcium and phosphorus

from enamel by dilute acids.

Scott, 1960 Stannous ions form a coating on enamel surface

Brudevold, 1967 Coating by stannous ions has no protective action against the

carious process and may actually reduce fluoride uptake

Clinical studies:

Muhler, Gish and Howell,1962 conducted a 5 year study(1957-62) to compare

8%Sn F2(single annual application) and 2%NaF(4 annual applications) and

every 3 years. After 5 years, caries increment in SnF2 group was approx. 35%

less than increment in NaF group.

Author Study period Reduction in DMF

surfaces(%)

Compton et al.(1959) 1 28

Jordan et al.(1959) 2 38

Law et al.(1961) 1 24

Mercer and muhler

(1961)

1 51

Burgess et al.(1962) 2 29

Harris(1963) 1 23

Torell(1965) 1 none

Wellock et al.(1965) 1 none

Horowitz and lucye

(1966)

2 none

Houwink et al.(1974) 9 37

General features:

Undergo rapid hydrolysis and oxidation, thus must be prepared freshly

for each treatment.

Causes brown discoloration of teeth particularly in hypocalcified areas

and round margins of restorations. The problem seems to be worse in

patients with poor oral hygiene

Can cause reversible gingival irritation in patients with poor gingival

health

As it is unstable in aqueous solution, it has to be freshly prepared for

each treatment.

Disagreeable taste. As SnF2 is very reactive, so flavoring to mask the

taste is contraindicated.

Acidulated phosphate fluoride:

Introduced in 1963, by Forsyth Dental Center as acidified sodium

fluoride solution, based on premise that greater fluoride is taken by

enamel under acidic conditions.

APF has pH of 3.0,buffered with 0.1M phosphoric acid and contains a

fluoride concentration of 1.23%

Acidic taste due to acidic pH. But flavoring can be done.

Stored and is stable in plastic container because it may etch the glass if

stored in glass container.

Repeated or prolonged exposures of porcelain or composite restorations

to APF can result in surface roughening and possible cosmetic changes.

In 1947 Bibby reported that as ph of the solution was lowered fluoride

was absorbed into enamel more effectively.

Brudevold et al 1963 studied the effect of prolonged exposure of enamel

to sodium fluoride in acid sodium fast solutions.

They concluded that the fluoride concentration in enamel increased with

decrease in ph of solution.

Mellberg(1966) reported that after a 10 min exposure of a cut tooth

section to APF sol, there was a high fluoride conc. In the inner layers of

enamel.

Clinical studies

o APF sol, containing 1.23% available fluoride in 0.1M phosphoric

acid at pH 2.8 are applied in a similar manner to SnF2 sol. The first

clinical trial was started in 1961 by Wellock and Brudevild(1963).

After 2 years, children in the study group had approx. 66% fewer

carious surfaces than children in control group.

o Parmeijer, Brudevold and Hunt(1963),in a study of 77 children

aged 4-10 years, compared the effectiveness of neutral NaF

solution with an APF solution, used on opposite sides of the

mouth. on the right side(APF), 45 new DMF surfaces were

recorded whereas on the left side(NaF),92 new surfaces were

found. In this study, it was concluded that APF was 50% more

effective than neutral NaF as a caries preventive agent.

o Further studies have reported reductions of 44-49% in new DMF

teeth in children given annual or bi-annual applications of APF

solution compared with control groups receiving treatment with tap

water only(Wellock,Maitland and Brudevold,1965;Cartwright,

Lindahl and Bawden,1968).

o Szwejda, Tossy and Below(1967) carried out the clinical trial of

APF gels on seven years old children. They observed no reduction

in caries increment after 1 year.

APF gels:

Available as thixotropic gels ie. they convert to a solution and flow more

easily under pressure

Gentle pressure should be maintained on the tray to force gel

approximally.

Gelling agent used is usually methylcellulose or hydroxyethyl cellulose.

Szwejda, Tossy and Below(1967)- first published trial of APF gels on 7-

year old children.

Fluoride varnishes: Duraphat was the first fluoride varnish introduced in

1960s. The varnishes were originally developed to prolong the contact time

between fluoride and enamel3. The varnishes adhere to the tooth surface for

longer

periods and prevent the immediate loss of fluoride after application, thus acting as

slow-releasing reservoirs of fluoride. Caries reductions by fluoride varnishes have

been similar to those reported for fluoride solutions and gels (DeBruyn and

Arends, 1987; Seppa, 1989; Ripa, 1990).3

Advantages:

Safe to use: Because the amount of varnish usually used is 0.3-0.5mL,

which delivers only 3-6mg fluoride.

Application:

Usually biannual applications of varnish are the most widely recommended.

Instructions to patients:

Not to eat or brush for at least 4 hrs after varnish application.

The comparison between Duraphat and Fluorprotector is as under:

Properties Duraphat Fluorprotector

Introduced in 1960s 1970s

General consistency Viscous resinous lacquer Polyurethane-based

lacquer

Fluoride content 5%wt sodium fluoride

(2.26% fluoride)

5 wt% difluorosilane

(0.7% fluoride)

pH Neutral Acidic

Application Applied to dry,clean teeth.

Hardens into a yellowish

brown coating in presence of

saliva

Leaves a clear

transparent film on the

teeth

Efficacy 30-40%(Permanent teeth)

7-44%(Primary teeth)

1-17%

Other varnishes:

DuraFlor: Another name for Duraphat

Carex:

1.8% fluoride

Efficacy similar to Duraphat

Self applied fluorides

o Self applied topical fluoride gels:

0.05% gel(5,000ppm F) daily self application for 5 min is effective means of

caries reduction

Custom fitted maxillary and mandibular trays (Toplicators) are fashioned by

vacuum drawing heat-treated sheets of polyvinyl over plaster models of the

teeth. Intermittent biting pressure on plastic trays tends to pump the gel into

pits, fissures and interproximal spaces.

Disadvantage:

o Relatively high cost of fabricating individual trays for each patient

o Dependence on the patient’s cooperation.

This procedure, first tested in supervised school programs, reduced decay in

a nonfluoridated community by about 75% and in fluoridated community by

about 30% after 2 yrs.(Englander H.G. et al 1967,1971).

0.4% stannous fluoride gel(1,000 ppmF) has been used as an alternative.

Many of these stannous gels have been accepted by ADA Council on Dental

Therapeutics.

Fluoride mouthrinses:

20-50% effective in reducing caries

The rinse should be swished between the teeth for 1 min and then

expectorated.

Advantages:

o Safe

o Effective

o Relatively inexpensive

o Easy to learn

o Requires little time

o Can be supervised by non dental personnel in school settings.

0.2% sodium fluoride(900ppm F) for 1 min- biweekly use

0.05% sodium fluoride(230ppm F) for 1 min- daily:

o More effective

Available as over-the- counter product. The label states that use is restricted

to persons 6 yrs old and older.

Fluoride dentifrices:

Sodium monofluorophosphate (MFP) was first tested as a therapeutic agent

in dentifrices in early 1960s. Numerous clinical trials of dentrices containing

0.76% or 0.8% MFP have since been conducted by different groups in

various countries showing approx. 25% effectiveness in caries reduction.

Toothpastes containing 1000 ppm fluoride

Investigators Active

ingredient(%

conc.)

pH Duration(yr) Age(yr) Statistically significant

reductions in carious

surfaces

saved %

redn

P

Brudevold

and Chilton

0.22% NaF+ 4.8-

5.3

2 11-17 1-2 * 0.01

Peterson

and

Williamson

1.5% soluble 4.8-

5.3

2 9-15 1 * *

Slack et al. orthophosphate * 3 11-12 - - -

Zacherl 0.22% NaF 5.5 1.66 7-14 - - -

Investigators Duration

of Trial

No. of

carious

surfaces

saved per

year

Reduction in

carious

surface

increment(%)

Level of

statistical

significance

Muhler et al. 1 yr 1.48 49 0.0001

Muhler et al. 1 yr 0.87 36 0.013

Muhler and

Radike(Adults)

2 yr 0.84 34 0.005

Jordan and

Peterson

2 yr 0.28 13 NS

Muhler 2 yr 0.46 21 0.01

Kyes et al.

(Adults)

3 yr 0.6 63* 0.0001

Bixler and

Muhler

2 yr 0.18 8 NS

Muhler 8 mo 1.8 45 0.006

Muhler 3 yr 0.41 22 0.0062

Finn and

Jamison

2 yr 1.2 46 -

Slack and

Martin

2 yr No true

placebo

No true

placebo

-

CONTENTS

Introduction to fluorides

Sources of fluoride

Metabolism

Absorption

Distribution

Excretion

Mechanism of action

Professionally applied fluorides

o Solutions

Sodium fluoride

Stannous fluoride

APF

o Gels

o Foams

Self applied fluorides

o Gels

o Mouthrinses

o Dentifrices

References

Fluorides in caries prevention- Murray

Fluorides in dentistry- Fejerskov

Dental caries- the disease and its clinical management- By Fejerskov

B. Øgaard, L. Seppä and G. Rolla. Professional Topical Fluoride

Applications-- Clinical Efficacy and Mechanism of Action. ADR 1994 8:

190

JADA, Vol. 131, July 2000

JADA, Vol. 132, September 2001

Caries research 1998; 32:83-92

Journal Of Minimum Intervention In Dentistry, 2009; 2 (4) 225