FLUORIDES
Fluoride is the ionic form of the element fluorine, the 13
thmost abundant element in the earth's
crust.
Fluoride is most electronegative, higly reactive anion with atomic weight 19 and atomic number of 9.
Its selective effect on hard tissues of the body
attributes significantly to prevention and control
of dental caries.
OCCURENCE IN NATURE
The major fluoride containing mineral is Fluorite or Flourspar (CaF
2), which contains 48.8% of
Fluoride.
Cryolite (Na
3AlF
6)is a relatively rare mineral.
Fluorapatite (Ca
10[PO
4]
6F
2has 3.8% of Fluoride.
Main component of rocks.
Because of universal presence of fluoride in the earth’s crust, all waters contains varying
concentrations of fluoride.
FLUORIDE IN THE ENVIRONMENT
IN LITHOSPHERE
ROCK MINERALS (>50)
EARTH CRUST (300ppm)
SOIL
(500ppm)
VOLCANO
IN BIOSPHERE
PLANTS (2-20mg/g)
LEAFY VEGETABLES (11-26 mg)
ANIMAL FEED
IN HYDROSPHERE
GROUND WATER
LAKE WATER (150mg/kg)
SEA WATER (15-18mg) RAIN WATER
IN ATMOSPHERE
AMBIENT AIR (0.16mg/m2
THROUGH TECHNOLOGY (0.05- 1.8micrograms/m2
GROUND LOFTY MOUNTAINS
SOURCES OF FLUORIDE
Principal source is water
Derived from plants, marine animals and dust particles.
Fluoride content in fishes mainly dried salmon and dried mackerel 84.5ppm
Potatoes give 6.4ppm
Tea contains 97ppm.
Metabolism and site of absorption
Fluoride is passive in nature, and no active transport is involved in the process.
The maximum plasma fluoride concentration reached within 60 minutes.
Absorption occurs mainly in the stomach.
The absorption can also occurs from the lungs by inhalation of fluoride dust and gases.
A third and very rare route of absorption is through skin. It occurs when hydrogen fluoride is applied in the skin, which is readily and completely absorbed.
EXCRETION OF FLUORIDE
Excretion via kidneys – most important route for the removal of fluoride from the body.
- Urinary fluoride is 30% of fluoride in renal patient and 50-60% in normal persons.
- 40-60% of the single fluoride dose is excreted in the urine during 24 hours.
Excretion via the gut
Under normal circumstances, about 10% of the total fluoride intake is excreted in faeces.
The faecal fluoride is low.
The antacid aluminum hydroxide is commonly
used to decrease the serum phosphorus level
and inhibits the internal absorption of fluoride.
Mechanism of action
A number of mechanism have been identified which are assumed to work simultaneously & can be grouped as follows -
1. Increase enamel resistance or reduction in enamel solubility
2. Increased rate of posteruptive maturation
3. Remineralization of incipient lesion
4. Interference with plaque microorganism
5. Modification in tooth morphology
• Increase enamel resistance or reduction in enamel
solubility - When enamel is exposed to a pH of about 5.5 or lower , it will dissolve.
This occurs beneath a bacterial plaque. The
con. of calcium , phosphate & other ions in the solution will increase.
Carious dissolution of enamel is a cyclic phenomenon
consisting of phases of demineralization & reprecipitation.
The presence of F reduces the solubility of enamel by
promoting the precipitation of hydroxyapetite & phosphate mineral .
Fluoride continues to enter the enamel surface, casting crystals to change from predominantly apatite and
hydroxyapatite to fluorapatite (FAP) and fluohydroxyapatite (FHAP) crystals.These fluoride rich crystals are less acid soluble than the original enamel apatite.
Increased rate of posteruptive maturation : fluoride increases the rate of mineralization or post eruptive maturation.
Organic material is also deposited into the enamel surface to further increase its resistance to dental caries. Both mineral ions & organic material are deposited from the saliva. A less soluble tooth that is more resistant to acid attack & less prone to caries is formed .
Remineralization of incipient lesions : remineralization is a dynamic process that results in reduced enamel solubility.
Fluoride plays a critical role in reducing dental caries by enhancing remineralization.
This increase in enamel resistance is achieved through the growth of crystals which became larger than those in either demineralized or sound enamel. These larger crystals are more resistant to acid attack.
Interference with plaque microorganism
Studies done on S. mutans indicate that the following are inhibited by fluoride –
1. Enolase & therefore the PEP phospo transferase system.
2. Bacterial phosphatase which are involved in degradation of sugar phosphatase.
3. Cation (potassium) transport which is closely associated with carbohydrate metabolism.
In high con. F is bactericidal , in lower con. it helps control the growth of bacteria without destroying them (bacteriostatic)
Modification in tooth morphology: the size & morphology of teeth in human & experimental animal can be influenced by ingestion of fluoride.
Most reports indicate that diameter & cusp depth of teeth are smaller if fluoride is present during tooth development . Such changes in morphology would tend to decrease the caries
susceptibility of teeth by making them more self cleansing.
Mode of fluoride administration
Systemic Topical
Dietary fluoride Salt fluoride
Fluoride in sugar
Dietary fluoride supplement Fluoride drops
Fluoride drops with vitamins Fluoride tablets
Fluoride tablets with vitamin Fluoride sustained release Fluoride device
Fluoride rinse solution
Water fluoridation
School water fluoridation Milk fluoridation
Professional application Fluoride solution
Varnish Foam Gel
Self
application
Process of adjusting the amount of fluoride in a community water supply to an optimum level for the prevention of dental caries and a clinically
insignificant level of fluorosis.
The adjustment of fluoride concentration in drinking water to an optimal level of 1ppm is associated with marked decrease in dental caries.
Water Fluoridation
The recommended daily dosage of fluoride for children above 3 years of age is 1mg.
This can be obtained by drinking 1 lt of water with a concentration of 1ppm
fluoride ion.
Fluoride compounds in community
water: NaF was the first compound used
in controlled fluoridation program.
Recommended level of fluoride in water (WHO)
Concentration 0.7-1.2ppm
Depending upon community mean maximum daily temperature:
Cold climate – 1.2ppm
Summer season - 0.7ppm.
Calculation of optimum level of fluoride
ppm fluoride = 0.34/E
E = -0.38+0.0062 x temp in
0F
(E is estimated water intake)
Benefits of water fluoridation
Some tooth surfaces receive greater protection, i.e. smooth surfaces of teeth, especially proximal surfaces.
Have both pre-eruptive and post eruptive effect.
Act systemically during tooth formation to make enamel more resistant and also have topical
effect through release in saliva after ingestion.
Change morphology of occlusal surface by
making pits and fissures more shallow and self
cleansible.
Community water fluoridation is least expensive and most effective method.
Accurate information regarding fluoride
concentration can be achieved from the
sample of water.
Alternatives to water fluoridation
School water fluoridation:
- It is the adjustment of the fluoride concentration of a school’s water supply for caries prevention.
- It provides maximum cariostatic effect in developing teeth.
- Since children spend 6-8 hrs in the school,
concentration of fluoride must be 4-6 times higher than that for community water fluoridation.
The school water is fluoridated at a concentration
of 4.5 to 6.3ppm.
Advantages & disadvantages
It is effective public health measure to reduce dental caries in community where fluoridation of water supply is not possible.
Disadvantage: child usually start going to school at the age of 5-6 years, so there is no pre-
eruptive contact to primary teeth.
There is intermittent exposure as the children
are in school for 6-8 hrs and less than 180 days
per year.
Defluoridation
Defluoridation means to improve the quality of water
with high fluoride concentration by adjusting the optimal level in drinking water .
In india , the first work on defluoridation was done by National Environmental
Engineering Research Institute(NEERI) at Nagpur in 1961
Achieved by two methods
1) Ion exchange process or adsorption
2) Addition of chemicals to water
Adsorption and ion exchange method
Some substances adsorb F ion by the surface, & it can exchange its negative ion e.g OH group for fluoride ion. Thus conc. of fluoride in water decreases.
This depends on suitable conditions like pH, temperature, flow rate, grain size of the material.
Material used
Activated alumina
Activated bauxite
Tricalcium phosphate
Hydroxy apatite
Cation exchange resins
De
fluoron 1 : a sulphonated saw dust impregnated with 2% alum solution . Carbion : it is a cation exchange resin of good durability
& can be used on sodium & hydrogen cycles .
Magnesia : it removed the excess fluoride but pH of treated water was beyond 10 & its correction by
acidification or recarbonation was necessary .
Defluoron – 2 : developed in 1968. It is a sulphonated coal & works on the aluminum cycles .
Precipitation method
In a high pH condition , co-precipitation of several elements in water with fluoride ion forms fluoride salts.
Thus the fluoride conc. in water decreases .
Alum is the well known substance of this group. It is used in water supply system & water treatment.
Methods based on membrane separation
Reverse osmosis
All elements in water get diminished after filtration
Best purification method
30% of raw water is lost , hence seems to be expensive for developing countries.
Nalgonda technique of defluoridation
It involves addition of 2 readily available chemicals . The process comprises addition in sequence of lime , bleaching powder & filter alum to the fluoride water followed by flocculation , sedimentation & filtration.
The technique is extremely useful both for domestic as well as for community water supplies .
Mechanism of defluoridation :
Rapid mix – it is an operation by which the coagulant is rapidly & uniformly dispersed through out single or multiple phase system. This helps in the formation of microflocs & results in proper utilization of chemical coagulant, preventing localization of concentration &
premature formation of hydroxides.
Flocculation : it is the 2nd stage of the formation of settlable particles (flocs) from destabilized colloidal sized particles & is achieved by gentle & prolonged mixing.
Sedimentation : it is the separation from the water by gravitational setting of suspended particles that are heavier than water .
Factors that influence sedimentation are :-
i. Size, shape, density & nature of the particles.
ii. Viscosity , density & temperature of water.
iii. Surface overflow rate.
iv. Velocity of flow.
v. Effective depth of settling zone.
Filtration : it is a process for separating suspended &
colloidal impurities from water by passage through porous media.
Procedure:
Raw water is mixed with adequate lime & alum. Amount of lime depends on the alkalinity of raw water. If raw water has adequate alkalinity, the lime addition is not required.
Alum solution, is added after the addition of lime, stirred gently for 10 min & the flocs formed are allowed to settle.
Advantages :
1) Can be used both domestic & community levels.
2) Cost effective
3) Chemicals are same as those used in a municipal water supply
4) Designs are flexible to use at different location
5) Operations are possible manually
FLUORIDE
SUPPLEMENTS
F
FLUORIDE THERAPY THE REFERENCE MANUAL OF PEDIATRIC DENTISTRY AAPD 2018
Fluoridated milk
Fluoridated milk may be produced in a no. of different forms ; liquid (pasteurized & sterilized) & powder.
Compounds which have been used to fluoridate milk include sodium fluoride, calcium fluoride, disodium monofluorophosphate, & disodium silicofluoride.
The conc. of fluoride required in the product is dictated by the fluoride dose to be delivered to the recipient child.
NaF is added to milk in the form of a concentrated solution using a fixed volume ratio to obtain the required product. Disodium monofluorophosphate too is added to pasteurized milk in the form of a concentrated solution .
Monofluorophosphate reacts with calcium to form a complex calcium monofluorophosphate, but this is more soluble than calcium fluoride.
Milk fluoridation has the advantage of being selective because children under the age of 14 yrs need to drink milk.
Disadvantages:
1.
Fluoride is incompletely ionized in milk.
2.
Absorption is lower than that with water.
3.
Wide variation in intake of milk.
4.
Require parental or school effects, technical
difficulties, problems of distribution, and high
cost.
Dietary fluoride
Fluoridated salt:
Feasible way to deliver fluoride.
Wespi (1961) first promoted use of table salt for fluoride supply.
Initially supplement was 90mgF/kg of salt.
Recently, it is recommended in the range of 200- 250mgF/kg salt.
Commonly used salt are potassium fluoride (250mg/kg) and sodium fluoride (225mg/kg).
6 countries have specific policies for use of salt
fluoridation: Belgium, France, Germany, Spain,
Switzerland and Hungary.
Advantage and disadvantage
Advantage: Extremely low cost, negligible waste of Fluorine, ease of implementation, and free choice for individual’s household.
Disadvantage: Fluoride supply is usually
ingested with meals hence resorption is
relatively slow.
Topical fluoride
Topical Fluorides” is used to describe those delivery systems which provide fluoride for a local chemical reaction to exposed surfaces of the erupted dentition: the delivery systems include measures designed for professional application in the dental office, as well as systems designed for supervised home use.
Topical fluoride products – 1. Professionally applied
2. Self applied
SODIUM FLUORIDE
Knutson and Feldman (1948) recommended a technique of 4 applications of 2 percent NaF at weekly intervals in a year at 3, 7, 10 and 13 years.
Sodium fluoride has neutral pH, 9200 ppm
of F–
Method of Preparation- Two percent NaF solution can be prepared by dissolving 20 g of NaF powder in 1 liter of distilled water in a plastic bottle.
Ready-to-use 2% solutions and gels of
NaF are commercially available.
Stannous fluoride (SnF2)
Dudding and Muhler in 1957 tried single annual application of 8 percent SnF2 and reported 32 percent caries reduction.
which is obtained by dissolving 0.8 g of
powder in 10 mL of distilled water.
Stannous fluoride solution has to be
freshly prepared before use each time
(stannous form of Tin gets oxidized to
stannic form, thus making the SnF2
inactive for anticaries action), as it has no
shelf life.
Limitations-
Solutions have a bitter, metallic taste.
contraindicated for esthetic reasons.
Temporary brownish pigmentation of carious tooth structure.
Ready-to-use solutions or gels with the
proper SnF2 concentration, however, are
not commercially available.
Acidulated phosphate fluoride (APF)
Finn Brudevold and his coworkers
concluded that semiannual application of
1.23 percent APF for 4 minutes is helpful
in reducing caries by 28 percent.
Dissolve 20 gms of NaF in 1 liter of 0.1 M phosphoric acid, to this add 50% hydro fluoride acid to adjust the pH at 3.0 and F concentration at 1.23%.
Methylcellulose or Hydroxyethyl cellulose is
to be added to the solution and the pH is to be
adjusted between 4 to 5.
Application of Topical fluorides
Application of Solution-
a. Sodium fluoride is applied once and allowed to dry for 4 min. The fluorides absorption from the enamel is cut off after initial absorption and it is termed “choking- off” reaction.
b. Stannous fluoride and APF solution is continuously painted onto the tooth surfaces.
Fluoride gels applied with a disposable tray.
Dental prophylaxis prior to the topical
application of fluoride must be considered
optional; it should be performed if there is
a general need for a prophylaxis, but it
need not be performed as a prerequisite
for topical fluoride applications.
Armamentarium-
Cut cotton rolls
Suitable cotton-roll holders
Cotton applicators
Treatment solution
Procedure
A 4-min treatment time has been typically recommended for professionally applied topical fluoride solutions, gels, or foams.
They are less effective than fluoride
varnish.
If gel or foam is applied with a tray technique, the trays should be about one-third full for gel and one-half full for foam.
Both upper and lower trays are inserted at
once to complete the topical fluoride
treatment in one 4-min application.
The patient sits in an upright position with his/her head tipped slightly forward to allow excess saliva and fluoride to flow toward the lips.
With a saliva ejector inside the patient’s
mouth, the tip is moved to help control
drooling and the swallowing of fluoride.
The dentist or appropriate office staff should supervise the treatment and provide assistance as needed.
The patient should be encouraged not to
eat, drink, or rinse for 30 min after the
treatment to maximize fluoride uptake in
enamel.
Application frequency-
Objective - Provide protective benefits to
“the permanent teeth during the period of changing dentition.”
Knutson technique- topical application of sodium fluoride consisted of a series of four applications provided at
approximately 1-week intervals.
The series of applications be administered
at ages 3, 7, 10, and 13 years.
When stannous fluoride and APF were subsequently developed, it was administered as single applications provided at 6- or 12-month intervals.
Patients with little evidence of existing or
anticipated caries should be given single
applications every 12 months as a
preventive measure.
Fluoride varnishes
Fluoride-containing varnishes contain
5.0% sodium fluoride (2.26% fluoride),
and a typical application requires only
0.3–0.5 mL of the varnish, which contains
3–6 mg of fluoride.
The first fluoride varnish was introduced in Europe in 1964 and contained 5.0%
sodium fluoride (or 2.26% fluoride, equivalent to 22,600 ppm).
The application procedure involves
cleaning the tooth surfaces by
toothbrushing, painting the varnish on the
teeth, and drying.
The varnish is retained for 24–48 h during which time fluoride is released for reaction with the underlying enamel.
The varnish is applied with a soft brush,
with reapplications recommended at 3–6-
month intervals depending on caries-risk
assessment.
Fluoride rinses
Fluoride mouth rinses is a simple and quite popular way to exposed enamel surface to fluoride.
Amount of fluoride:
Non prescribed ones contain 0.05%NaF( about 222 ppm) – they should be swished once a day vigorously for 1 minute and expectorated.
Prescribed ones generally contains 0.2%
NaF (about 900ppm) – they are used
under supervision, once a week for one
minute.
FLUORIDE TOOTH PASTES
Fluoride compounds commonly used are – Monofluorophosphate
Sodium fluoride Stannous fluoride Amine fluoride
Optimum fluoride concentration
For child up to 6 years of age : 500 ppm
Above 6 years of age : 1100 to 1500 ppm
UP TO 2 YEARS OF AGE
- No fluoridated tooth paste
UP TO 3 YEARS OF AGE
- Tooth paste of size less than of smear layer or rice grain
3 TO 6 YEARS OF AGE
- Pea size
FLUORIDE TOXICITY
Dental fluorosis occurs in human being
consuming drinking water containing up to 8 ppm fluoride, about 8 times the
recommended amount.
Or by consuming water containing
2.0mg/lt or more fluoride particularly during first eight year of life. Skeletal
fluorosis can occur if water contains more than 4ppm of fluoride and is consumed
daily.
Acute toxicity
The amount of 35-70mgF/kg body weight of soluble fluoride is to be lethal.
This is equivalent to 5 -10gms of NaF for an adult weighing 70mg or about 1.0 to 2.0 gm NaF for a child of 15 kg.
Signs and symptoms:
nausea, vomiting, diffuse abdominal pain,
diarrhoea, excess salivation, thirst, muscle
tremors
Treatment
Vomiting should be induced
Fluoride binding liquids like warm water, Calcium hydroxide liquid, antacid containing aluminum or magnesium hydroxide or milk( to decrease
absorption).
Hospitalization with thorough stomach wash with additional lime water.
If muscle tremor, Calcium gluconate should be
administered intravenously, along with saline to
prevent shock.
Chronic toxicity
It is due to long term ingestion of smaller amount of fluoride which usually effect the hard tissue and kidney.
Effect Dosage Duration
Dental fluorosis 2 time optimal Until 5 years ( excluding third molars)
Skeletal fluorosis 10-25mg/day 10-20 years
Kidney damage 5-10mg/day 6-12 months
Lethal and safe dosage of fluoride
Certainly Lethal Dose (CLD) 5-10gm NaF or 32-64 mgF/kg
Safely Tolerated Dose (STD) ¼ CLD or
1.25-2.5 gm NaF or 8-16 mgF/kg
Fine white striae
Snow – cap phenomenon
Lines – broader and more pronounced Merging of lines;
-Small irregular, cloudy paper-white areas Entire tooth surface exhibits:
-distinct, irregular, opaque or cloudy white areas Brown stains – post eruptive staining
Entire tooth surface appears chalky Focal areas of enamel loss – pits Pits merge to form horizontal bands Total loss of tooth structure
fluorosis
Deans fluorosis index
score criteria
0 Normal enamel
0.5 Questionable mottling –few white flecks & spots
1.0 Very mild mottling-small opaque paper white areas,<25%
2.0 Mild mottling-extensive white opaque areas,<50%
3.0 Moderate mottling –all enamel surfaces affected, Attrition and marked wear. Brown stain
4.0 Severe mottling – all enamel surfaces affected, hypoplasia , discrete or confluent pitting, brown Stains, corroded appearance.
F level duration Effects
0.7-1.2ppm Depends on temp Prevent dental caries
1.5-3.0ppm 5 to 10 years or more Mild dental fluorosis
3.0-8.0ppm 15 to 20 years Severe form of dental fluorosis Milder skeletal fluorosis
8.0ppm 5-10 years Severe dental and skeletal
fluorosis
Skeletal fluorosis
Common in workers of aluminum factory
Endemic fluorosis :India, China, South Africa
Fluoride dosage: 10 to 25 mg/day for a period of 10 to 20 years
– First stage: asymptomatic (radio graphically – increase density of vertebrae pelvis)
– Advanced cases: bone density increased
bone contours and trabeculae uneven and blurred
extremities show thickening of compact bone irregular periosteal growth ( exostoses and
osteophytes)
increase in calcification in ligaments,
At this stage complaints: vague pain in small joints , knee joints and joints of spine
Increased severity “crippling fluorosis”:
stiffness of spine
limitation of movements
severe pain
References
1. TEXTBOOK OF PEDIATRIC DENTISTRY- NIKHIL MARWAH.
2. MCDONALD AND AVERY’S DENTISTRY FOR THE CHILD AND ADOLESCENT. JAFFREY A. DEAN, SECOND SOUTH ASIA EDITION.
3. ESSENTIALS OF PUBLIC HEALTH DENTISTRY-SOBEN PETER.
4. FLUORIDE THERAPY. THE REFERENCE MANUAL OF PEDIATRIC DENTISTRY AAPD 2018 .
