Transcript
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
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