fluoride mechanism and type of application

1. Systemic Fluoride
In prevention of dental caries
Systemic fluoride was used to prevent dental caries back to
as early as 1874. Fluoride ions convert to [hydrofluoric acid]
(HF) at pH 1.0-2.0 in the gut and are rapidly absorbed. Nearly
all (99%) of retained Fluoride is incorporated into developing
bones and teeth in the mineral, making the enamel crystals
larger and more stable&affecting the crown morphology
making the pits and fissures shallower and hence less likely
to create stagnation areas
BY
Dr.Marwa Laith Faris
2/20/2011

2. Systemic Fluorides
I ntroduction
The use of fluorides date back to as early as 1874 when the German
Erharde suggested the use of potassium fluoridetablets for expectant
mothers and children in order to strengthen teeth. This recommendation
was without any scientific evidence. What we now know to be dental
fluorosis (mottling) was noted by dentists long ago, who reported on
„Colorado Stain‟ without the etiology of the tooth defect being
established.
M etabolism and absorption
Fluoride ions convert to [hydrofluoric acid] (HF) at pH 1.0-2.0 in the
gut and are rapidly absorbed. Approximately 50% of ingested Fluoride
is excreted in the urine. A small amount is excreted in the feces, saliva
and sweat. Serum Fluoride levels peak within 1 hour of ingestion and
return to normal after approximately 3 to 5 hours. Fluoride accumulates
in patients with impaired kidney function and its retention is affected by
the acid-base balance: a diet rich in meat protein will producean acidic
renal filtrate and cause more Fluoride to be retained. Nearly all (99%)
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3. of retained Fluoride is incorporated into developing bones and teeth in
the mineral.
Fluoride exchanges with the hydroxyl groups of existing hydroxyapatite
crystals in bone to form fluorapatite (FA), which is less soluble in acid.
Tooth enamel with more FA is more resistant to acid erosion from
dietary acids and the weak acids produced by oral bacteria that cause
dental decay. Similarly, FA in bone makes it more resistant to
osteoclasts, which use protons to dissolve the mineral.
M echanisms of Action of Fluoride
The action of fluoride can give the following results:
*It has an effect during tooth formation making the enamel crystals
larger and more stable;
*It inhibits plaque bacteria by blocking the enzyme enolase during
glycolysis;
*It inhibits demineralization when in solution;
*It enhances remineralization by forming fluorapatite when in solution;
*It affects the crown morphology making the pits and fissures shallower
and hence less likely to create stagnation areas.
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4. The most important of these mechanisms is that, when fluoride is
present in the oral environment at the time of the acid attack, it inhibits
demineralization and promotes remineralization.The critical pH for
apatite is 5.5 and below this the calcium and phosphate ions pass out of
the enamel (demineralization). At pH = 7.0, apatite remineralizes and if
fluoride is present at this time fluorapatite forms (remineralization).
Fluorapatite is resistant to acid attack until the pH drops to 3.5.
Therefore, it is most important to have an intra-oral source of fluoride
when remineralization is taking place.In the past it was thought that the
systemic action of fluoride was important for caries prevention. This
view has completelychanged and it is now known that it is the topical
action of fluoride that is essential for caries prevention.
It is the presence of fluoridein the liquid phase at the plaque-
enamelinterface that is of most importance.Studieshave shown that even
lowlevels of fluoride (0.01 ppm) wereeffective in preventing the
dissolutionof enamel. It has been stated that it isthe activity of the
fluoride ion in the oralfluid that is important in reducing thesolubility of
the enamel rather than ahigh content of fluoride in the enamel.
Saliva, the fluid that bathes the teeth,has been extensively studied. The
levelof fluoride in saliva is thought to beimportant for caries prevention
and ithas been shown that subjectssusceptible to caries had salivary fluoride
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5. levels of <0.02 ppm, whereascaries resistant subjects had levels of>0.04
ppm.
There are a vast number of fluorideproducts that are available for
systemicand topical use. Systemic fluoride can be described as follows:
A -Water Fluoridation
This is a systemic method of providingfluoride on a community basis. Over
300million people worldwide receivenaturally or artificially
fluoridatedwater. In 1942, Dean et al.showed 1.0ppm fluoride to be the
optimum level.This was in a pre-fluoride era andperhaps the optimum level
needs to bereviewed. There have been 113 studies in 23 countries over the
last 50 years13showing that dental caries is reduced by50%. It is cheap and
cost-effective but there are opponents to its use. In some countries school
water has been fluoridated, but a concentration of 5ppm is required to offset
the less frequent intake.
B - Fluoride Supplements
These are in the form of:
I-Tablets anddrops.Caries reductions vary from 20 - 80%.There is
usually very poor patientcompliance, especially for high caries-risk
groups. A „Catch 22‟ situation is thecase in which those patients that
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6. arecompliant do not need supplements,whereas those that will benefit
will nottake them.
The doses vary worldwide and are being increasingly heldresponsible
for the rise in fluorosis. Thefluoride supplement doses depend on the
age of the patient and the level offluoride in the drinking water.
Nosupplements should be prescribed if the water fluoride level is
greater than 0.7 ppm.
The tablets should be allowed todissolve slowly in the mouth,
thusproviding a topical application offluoride to the teeth. There are of
course other systemic methods for providingfluoride to the community.
These are:
II-Salt;50% reductions in Switzerland and Hungary;
III-Milk;15–65% reductions;
IV-Mineral Water;46% reductions in Bulgaria.The fluoride levels of
bottled waters vary considerably, from 0.0-2.0 ppm mainly, but can be
as high as 10.0-13.0 ppm in some countries.
V- Sugar;Luoma showed decreased caries levels in animals and
humans when fluoride was added to sugar.
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7. There are, therefore, a number of sources of fluoride that we and our
patients may be exposed to:
*Water1.0 mg/day
*Supplements1.0 mg/day
*Diet0.5 mg/day
*Toothpaste0.25 mg/day (in children)
A dverse effect and toxicity
C hronic Toxicity
Before prescribing fluoride supplements we must first determine the
fluoride level of the patient‟s drinking water, the infant may be at
increased risk of developing dental fluorosis. The maxillary permanent
central incisors are most susceptible to fluorosis at about 2 years of age.
Dental fluorosis is a health condition caused by a child receiving too
much fluoride during tooth development. The critical period of
exposure is between 1 and 4 years old; children over age 8 are not at
risk. In its mild form, which is the most common, fluorosis appears as
tiny white streaks or specks that are often unnoticeable. In its severest
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8. form, which is also called mottling of dental enamel; it is characterized
by black and brown stains, as well as cracking and pitting of the teeth.
Fig. 1; A mild case of dental fluorosis (the white streaks on the
subject's upper right central incisor) observed in dental practice
Fig 2; A severe case of dental fluorosis, or "mottled dental
enamel."
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9. The „Halo Effect‟ is the term used to describe the ingestion of fluoride
from hidden sources. For example, fizzy drinks like Pepsi or Coca- cola
may contain fluoride if the bottling plant is in a fluoridated area and
therefore uses fluoridated water.
Other than dental fluorosis there are no known adverse effects of
ingesting fluoride on chronic basis at levels that are associated with
drinking water of concentrations of 4 ppm or less. These levels of intake
include fluoride not only in water but also in diet and in fluoride-
containg dental products.
Studies have shown that fluoride causes various histologicalstructure
changes of the kidney, including extensive induction of cell apoptosis,
resulting in impairment of renal function and metabolism, Fluoride
interferes with the formation of normal collagen, the protein cement
which holds body structures together.
Total collagen is increased, as much as 50% in one study, but the
collagen is imperfect. Structures heavily dependent upon collagen
include tooth enamel and dentin, bone, cartilage, and muscle and skin.
Finally signs of skeletal fluorosis may appear with high levels with
fluoride intake (8-10 ppm or higher in drinking water) for
approximately 10 years or more.
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10. A cute Toxicity
The Probably Toxic Dose (PTD) was defined by Whitford as the
minimum amount of fluoride ingestion that requires action, and is
5mg/Kg body
PTD for 1-2 year old child, ~ 10 kg (22 lb) = 50 mg F
PTD for 5-6 year old child, ~ 20 kg (44 lb) = 100 mg F
PTD for adult, ~ 60 kg (130 lb) = 3000 mg F (3 g)
The most popular unit: ppm = part per million
(wt/wt ; vol/vol)
Water with 1 ppm F = 1 mg/L
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11. At higher concentration, usually use
%(F-containing products)
1 % = 10,000 ppm
0.1 % = 1,000 ppm
0.05 % = 500 ppm
A mounts of dental products required to constitute the
PTD for a 5-year-old child
100 ml of an adult toothpaste (1000 ppm F)
440 ml of a daily F rinse (225 ppm F)
110 ml of a weekly F rinse (900 ppm F)
8 ml APF gel (12,300 ppm F)
4.4 ml F varnish (22,600 ppm F)
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12. S igns and symptoms of acute fluoride toxicity
Nausea
Vomiting
Hypersalivation
Abdominal pain
Diarrhoea
Convulsions (due to fall in plasma calcium)
Respiratory failure
Cardiac failure
Death
T reatment of acute fluoride toxicity
*Induce vomiting (to remove F)
*Give milk or 1% calcium gluconate orally toslow F absorption
*Advise hospital of acute F poisoning
R EFERENCES
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13. 1. K. Jack Toumba, Jinous F. Tahmassebi, RichardBalmer. Paediatric Dentistry in the New Millennium:
5. Clinical Prevention: The Role of the General Dental Practitioner
2. Zhan X-A, Wang M, Xu Z-R, Li J-X. Toxic effects of F on kidney function and histology in young
pigs. Research report Fluoride 39(1)22–26 January-March 2006
3.Yiamouyiannis, John, “Water Fluoridation and Tooth Decay: Results from the 1986-1987 National
Survey of U.S. Schoolchildren,” Fluoride, Journal of the International Society for Fluoride Research,
vol. 23, No. 2; April 1990; p. 55, pp. 28 33.
4. Murray JJ. Efficacy of preventive agents for dental caries. Systemic fluorides: water fluoridation.
Caries Res 1993; 27(Suppl. 1): 2–8.
5. Leverett D, Adair S, Shields C. Relationship between salivary and plaque fluoride levels and dental
caries experience in fluoridated and non-fluoridated communities. Caries Res 1987; 21: 179 (abstr. 57).
6. Fejerskov O, Thylstrup A, Larsen MJ. Rational use of fluorides in caries
prevention.ActaOdontolScand1981; 39: 241–249.
7. Martin J. Wagner. Absorption of Fluoride by the Gastric Mucosa in the Rat. J DENT RES 1962 41:
667
8. Dean HT, Arnold FA, Elvove E. Domestic water and dental caries. Public Health Report (US) 1942;
57: 1155–1179.
9. Angus C Cameron, Richard P Widmer. Handbook Of Pediatric Dentistry, first edition, 1997, chapter
3; Fluoride modalities.
Thank You
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