Mechanisms of Caries
Reduction by Fluoride
lecture -4-

Studies revealed that fluoride taken
systemically (before tooth eruption) and
topically (following eruption of teeth)
greatly reduces dental caries.
The precise and complete mechanisms of
actions F in relation to dental caries are not
fully understood.
There are three theories present explaining
this role:

1st theory (Pre eruptive theory):
This is a widely accepted theory claims that when
F is taken during the period of tooth formation
may cause changes in composition and
morphology of teeth.
Fluoride ions taken from surrounding tissue fluid
may replace the hydroxyl group of the
hydroxyapatite crystal forming a new crystal
known as fluoroapatite crystal.
Ca10(PO4)6(OH)2 + 2 F- Ca10(PO4)6 F2
+ 2 OH-

•2nd theory (post eruptive theory):
•F ions present in saliva and dental plaque
(from dental products; topical) will react
with the outer enamel surface to enhance
re-mineralization. Two types of reactions
may develop:
• The main reaction is formation of calcium
fluoride, while the 2nd type of reaction is
the formation of Fluoroapatite crystal.

•Calcium fluoride is not permanent
as it dissociated to calcium and F
ions.
•There for fluoridated products
need to be applied continually and
at a high concentration,
•These types of reactions can be
initiated at any time of subject life.

•The presence of F in high concentration (more
than 40 ppm) in dental plaque may affect the
growth and fermentation of bacteria.
•These by:
Interference with bacterial adherence by
retardation of extra cellular poly saccharide.
Inhibition of intercellular enzymes as enolase
and phosphatase. Thus inhibit the bacterial
glycolysis and metabolism.
In a high concentration, F is toxic to bacteria.

The general mechanisms where
by fluoride reduces dental caries
involve the followings:
•Increase enamel resistance or reduction in
enamel solubility (Inhibition of de-
mineralization)
•Re mineralization of incipient lesion.
•Interference with plaque microorganism.
•Improved tooth morphology.

Artificial water fluoridation
Controlled adjustment of a fluoride
compound to a public water supply in
order to bring the fluoride concentration
up to a level which effectively prevents
caries.

History of fluoride in
dentistry
• Dr. F. McKay begun extensive
(1901,1908) studies……Brown
stain……mottled enamel……now is
called Dental fluorosis.
•G.V. Black, USA in 1916
……histological studies on teeth
with brown teeth
…..hypocalcification with no dental
caries.
•H.V. Churchill …..analyses the
water ….high percentage of
fluoride in water (13.7 ppm).

History of fluoride in dentistry
Dr. H.T. Dean …dentist carry
out a series of
epidemiological studies…..
1 ppm…..
Inverse relationship
between dental fluorosis
and dental caries.

•Dental fluorosis:
•It is a developmental hypoplastic defect (;
hypoplasia) caused by excessive fluoridation
during the period of tooth formation. It is the
1st sign of chronic toxicity appears clinically as
a white spots or lines involving incisal edge or
cusps of posterior teeth or as a white opaque
or brown area, in sever cases a corroded
appearance will occur.

•Using light and electron microscopy, in
principle increased exposure to F during period
of tooth formation
•increased enamel porosity.
•porous enamel because of increase of inter
crystalline spaces;
•these spaces are occupied by water and
protein more than enamel.
•In more sever condition changes involve
enamel as well as dentin.
•break down of the outer enamel surfaces.

10
9
8
7
6
5
4
3
2
FLUOROSIS
0.0 0.5 1.0 2.0 3.0 4.0
DMFT
PPM F IN DRINKING WATER
slight
severe
moderate
mild
F in excess of 0.1mg/ kg body
weight = fluorosis

The optimal level
•The optimal level is (the level of F in drinking water
causing maximum reduction of dental caries but with no
clinical signs of dental fluorosis).
• Epidemiological and observational studies however
showed that a more sever dental fluorosis do develop
some times in certain area of hot climate at one part per
million, thus the optimal level of fluoride was changed
to 0.6 – 1.2 ppm according to the temperature. In
winter is 1.2 ppm and in summer is 0.6 ppm.

Communal water fluoridation:
•It is the controlled or artificial adjustment of the
level of F in a communal water supply to achieve
maximum reduction of dental caries and clinically
no significant level of fluorosis.
• Fluoride was 1st added to water supply in 1945 in
Grand Rapids (Michigan) while Muskegon was the
control.
•Caries reduction was reported to be 55%. In USA,
now more than 126000,000 people are receiving
systemic fluoridation. It is also applied in Europe
and other countries.

Artificial water fluoridation
Controlled adjustment of a fluoride
compound to a public water supply in
order to bring the fluoride concentration
up to a level which effectively prevents
caries.

GENERAL SYSTEMS FOR FLUORIDE
APPLILCATION (Lec.5)

Alternative to water fluoridation:

School Water fluoridation

##Supplements should be given daily, not
with milk
In prescription of F tablets several important
factors should be taken in consideration.
• - F content of the water supply,
(communal or bottled water). Applied only
in non F. area or those with low F. level.
• - Age of the child.
• - Co - operation of parents.
Fluoridated tablets (drops ).
NaF, 2.2mg (1 mg F).
1.1mg (0.5 mg)

•
•

Drops: 10 drops = 1 mg F/ L = 1ppm (also available in
0.125 mg, 0.25 mg and 0.5 mg/ L).
Another Program:
- Started at 3 years of age give 0.5 mg/day till 13 – 15
years.
- In presence of dental caries (0.25 mg/day till 3 years)
then 0.5 mg/ day till 13-15 years.
Instructions:
1- Given daily.
2- Tablets crushed between teeth.
3- Each bottle contains not more
than 264 tablets, to avoid acute toxicity after the accidental
ingestion of fluoride tablets.
4- Dentifrices used should be with out F, or with a low
concentration.

•Studies showed that tablet taken in the first 7
years of life provide reduction of 39% - 80%.
•Caries reduction in children was found to be
more in primary teeth when pregnant mother
taken fluoride,
•other studies showed no differences as placenta
regulates amount of fluoride reaching fetus.

Fluoridated Salt:
•It is controlled addition of F to domestic salt for
purpose of caries prevention.
• It was introduced first in Switzerland, 1955.
•It is considered next to water fluoridation
regarding caries reduction.
• F is added to salt inform of, KF or NaF in
different doses, 250 mg KF/ kg (or 225 mg NaF/
Kg) salt,
•based on adult salt consumption estimates of
daily salt, about one mg is ingested daily.

Advantages of salt fluoridation are;
•low cost
•ease of implementation
•no personal efforts is needed.
•Effective in caries reduction for permanent as well
deciduous teeth.
•Safe as there is minimum possibilities of dental
fluorosis.
Disadvantage:
• children would start to use salt too late in life, or
they used to take small amount of salt.
•Salt fluoridation need community education and
promotion,
•in addition there is international efforts to reduce
sodium intake for controlling hypertension.
•

Fluoridated milk:
•Human and bovine milk contain a low level of F
about, 0.03 ppm.
• Milk is a good food for infant and children, it is a
suitable vehicle for supplementary F to children, it
is an excellent source for calcium and
phosphorous in addition to vitamin D.
•Milk is essential for development of bones and
teeth.
• The concentration of F in milk is 2.5 ppm to 6
ppm, as calcium in milk may react with F reducing
the amount of free ionic fluoride actually
absorbed.

The bioavailability of F from milk is in similarity
to water, other studies showed that milk may
retard the absorption of F from GIT, but does not
prevent F absorption.
Fluoridated milk can be used in home and school
programs, with caries reduction of 70%.
•The disadvantages of milk fluoridation are the
high cost, thus the consumption of milk vary
between different socioeconomic level.
•Another disadvantage of milk, is that producing f
milk need a high level of expertise, explaining its
high cost.
• Some children dislike milk, for them a
fluoridated juice can be used.

Topical fluoride therapy:
• This term refers to the use of systems
containing relatively large concentration of
fluoride applied locally or topically to erupted
tooth surfaces in order to prevent or arrest
dental caries. The primary reactions product
involved the transformation of surfaces
hydroxyapatite to calcium fluoride.

•Calcium fluoride is a loosely bound fluoride,
dissolved rapidly and therefor to increase fixation
of fluoride it needs to be applied frequently and
continuously.
•The use of topical fluoridation started in 1940, to
control dental caries.
• The best time of application of topical agents is in
the post eruptive maturation period that is the
two years after eruption.
•Ionic exchanges continue between the oral
environment and outer enamel surface.

•1- Self – applied fluoride; a relatively low
concentration of fluoride applied by individuals
themselves. The concentration of fluoride is about
1000 ppm. This system includes:
•- Dentifrices
•- Mouth rinses
•- Fluoridated gel
•Agents can be used once or twice a day used once
or twice a day, and a combination of two types can
be applied.

Professionally applied fluoride
It is the periodic application of a high concentration of
fluoride to the erupted teeth by dentists or dental hygienist
The concentrations of fluoride are 9000 – 19000 ppm, it
may reach for some agents to 23000 ppm or more. This
system involves:
•Solutions
•Gel
•Varnishes
•Prophylactic paste(pumice)
•Others (; foam, slow- release device)
Agents can be applied periodically according to the need of
the patient (every three or six months) or once a year.

Efficacy of topical fluoride:
The concentration of fluoride used.
With increase of fluoride ions concentration in the topical
agents give more chance for reaction of ions with outer
enamel surface to enhance re-mineralization.
The frequency and duration of application.
Application of fluoride agent more than once daily (for self
- applied fluoride) or every three or six months (for
professionally applied fluoride), will increase the efficacy
and benefits of agents.
The specific fluoride agent or compounds.
The solubility of fluoride compounds differs thus affecting
the concentration of ionic fluoride release, thus the
benefits of the agent. Further, presence of other metal ions
as tin as for (SnF2) may enhance re mineralization
compared to other type of agents.

Self-applied topical fluoride
A-Fluoridated dentifrices
The first clinical trail of fluoridated dentifrices
initiated by Bibby 1942, the active agent was sodium
fluoride, and the abrasive was dicalcium phosphate
(DCP).
The general functions of these dentifrices are:
Physico – mechanical function; that is by the
action of the abrasive materials and the toothbrush.
Chemical function; that is by the reaction of
fluoride with the outer enamel surface and the
antimicrobial effect.

Types of fluoridated agents in
dentifrices include;
•Sodium fluoride (NaF).
•Stannous fluoride (SnF2)
• Sodium
monofluorophosphate (MPF)
•Amine fluoride
•Combination of NaF and MPF

•The range of fluoride concentrations in these agents is
500 – 1500 ppm.
•The content of fluoride in dentifrices will decrease with
the increase in the time of storage i.e six months or more.
• The type of fluoride agent used must be compatible with
the constituents of the tooth paste especially the abrasive
systems.
Types of abrasive;
•Ca- pyrophosphate
•Na- metaphosphate
•Silica
•Others

•Following brushing there will be retention
of fluoride in the oral fluid and dental
plaque. Fluoride ions released gradually in
the saliva and there by maintains a degree
of protections against caries.
•The increase in the frequency of brushing
will increase the benefits of fluoride.
Studies recorded caries reduction by using
fluoridated dentifrices about 25 – 30%.

•A brush full of 1000-ppm paste may
contain (1 mg F ions).
• Child may swallow pastes accidentally, at
this age the child cannot control muscles
of swallowing.
•Thus brushing twice a day with 1000 ppm
fluoridated paste the child may swallow
0.5 mg F/day.
•The child may be at risk to be affected by
dental fluorosis, especially in fluoridated
area or taking fluoride supplements.
•

Clinical recommendations for using fluoride
toothpaste in childern

•Twice daily use of fluoride toothpaste, in
combination with oral hygiene instructions, is the
cornerstone of any preventive programme for
children, irrespective of caries risk.
•Although the caries-preventive effect is recorded
only for concentrations of 1000 ppm and above,
toothpastes with lower concentrations (500-550
mg/g) may have some beneficial effects and could
be considered for children at low caries risk where
the risk of fluorosis is of concern.
•Brushing under supervision is essential.
•Note: mg/ g is equal to ppm.

Good practice points on brushing behaviour:
•Tooth brushing should be conducted so
each tooth surface is reached and
brushing should exceed 1 min, also in
preschool children.
•• Children should avoid rinsing with a lot
of water afterwards.
•• Children’s teeth should be brushed
using either a soft manual or power
toothbrush.

B-Fluoridated mouth rinses
It was started in the early 60,s of the last century.
Used for individuals, and in school programs.
It is indicated in following conditions:
Primary preventive programs for children and adults
In subjects with high risk to dental caries.
Patients with rampant caries.
Patients with hypo-salivations or xerostomia.
Patients with sensitive teeth due to tooth wear as
(abrasion, attrition, erosion) or because of exposed
root.
Patients with periodontitis and root caries.
Patients with orthodontic appliance.

Types of agents used:
Sodium fluoride, it is the main type used in
health programs, it is of two types neutral or
acidified (APF) forms in a water vehicle.
Concentrations 0.2% (900 ppm F) applied once a
week. 0.05% (225 ppm) applied daily.
 Stannous fluoride, Concentration 100, 200, 300
ppm.
Others, Amine fluoride or ammonium fluoride.
A 10 ml of rinse used by forcefully swishing of liquid
around the mouth for one minute then
expectorate.

Fluoridated mouth rinse should not be given:
•To children under six years of age, as they
cannot control muscles of swallowing.
•Children living in fluoridated area or receiving
fluoride supplements.
Studies reported a caries reduction about 30% by
the use of F rinse.
Note: Fluoridated mouth rinses should not
substitute fluoridated dentifrices, rinses is
usually supplement toothpaste.

C-Fluoridated Gel
•It is used in home programs.
Types of agents:
•Sodium fluoride or acidulated phosphate
fluoride (concentration 5000 ppm).
•Stannous fluoride (0.4%).
These can be applied using special tray or applied
directly to teeth by toothbrush.
Applied for 1- 5 minutes, then expectorate.
Patients advised not to rinse by water or eat or
drink for at least 30 minutes.

C-Fluoridated Gel
Indications for use:
Patients with rampant caries.
Patients with xerostomia.
Patients with sensitive teeth due to tooth wear
as (abrasion, attrition, erosion) or because of
exposed root.
Root caries.

C-Fluoridated Gel
•It can be used for four weeks course, when the
onset of the disease is stopped the patient can
switch back to mouth rinse.
•Fluoridated gel is not recommended for children
under 6-years of age.
• It is used in combination with dentifrice, and not
preferable to be used with mouth rinse.
•

Professionally applied fluoride:
#Medicaments typically dispensed by dental
professional in the dental office to prevent or
arrest dental caries.
#Materials applied are in forms of solutions, gel,
foam, varnishes, pumices, others (fluoridated
restorative materials, fluoride release devices).
•

Professionally applied fluoride:
Different agents are available as:
- Sodium fluoride
- Stannous fluoride
- Potassium fluoride
- Zirconium fluoride
- Titanium fluoride
- Others.
The concentration range of fluoride in these
agents is 9000 – 22000 ppm.
•

Professionally applied fluoride:
General method of application:
Techniques followed for application of fluoride in
the dental office are:
- Tray technique: a small amount of fluoride is
added to a tray then inserted in the patient mouth.
Trays come in different shapes and types as foam
lined or paper, custom vinyl etc.
- Paint on technique, by which fluoride material
applied to teeth by cotton applicator of brush.

For both techniques:
- Teeth are cleaned first (scaling and polishing) to remove dental
plaque, calculus, stain and debris. These may interfere with the
uptake of fluoride ions and reduce its effectiveness.
- Teeth are isolated using cotton roll and saliva ejector. The
patient seated in upright position with the head tilted downward
to avoid accidental swallowing of the materials .
- The fluoridated agent applied following dryness of teeth for 4
minutes (or according to manufacturer’s instruction). The amount
of agent used must not exceed 4 ml to prevent acute toxicity.
- Use un waxed dental floss to push the material between teeth.
- Following treatment ask the patient to expectorate several
times in disposable cup .
- Instruct the patient not eat or drink for at least 30 minutes.

Apply no more than 2-2.5 grams of gel
per tray (40% of the tray’s volume) no
more than 1/3 of the tray height

Indications of use:
In general materials indicated to be
used at any age in:
• -Prevention of dental caries
• -control of rampant caries.
•- Sensitive teeth and root caries.

These materials are available in form of
powder, solution or gel.
The concentration of fluoride is 2 %.
When powder is used 0.2 gram dissolved in
10 ml distilled water. When the agent is
added to outer enamel surface calcium
fluoride is formed. The following reaction
take place involves;
Sodium fluoride (NaF):

The CaF2 reacts with hydroxyapatite to
form fluoridated hydroxyapatites thus
increase the stability of crystals and
resistance to acid attack, furthermore it
will enhance the re-mineralization of initial
caries.

•These agents have a basic pH, chemically stable
when stored in plastic or polythene containers.
•It should not be stored in a glass bottle as a
fluoride ions will react the silica of the glass
forming silicon di oxide reducing the free ionic
fluoride necessary for caries reduction.
• A flavoring and sweetening agents however can
be added.
•These materials are not irritant to the gingival,
and do not cause discoloration to teeth.

Method of application:
•According to (Knutson,s technique),
NaF fluoride agents are added in a
series of 4 – weeks at ages of 3, 7, 11
and 13 years. Coinciding the eruption
time of permanent teeth and also for
protection of primary teeth.
•The one disadvantage of this agent is
that the patient need to visit dentist
four times to accomplish this
technique.

•The success of any topical fluoridated
agent depends on its capability of
depositing fluoride ions in the enamel as
fluoroapatite and not only calcium
fluoride.
• Fluoroapatite crystals are stable not like
calcium fluoride.
Acidulated phosphate fluoride (APF):

•There are two ways of speeding to the reactions that lead
to formation of fluoroapatite.
•1- Increase concentration of fluoride ions in the agent.
•2- Lowering the pH, that is making the solution more
acidic.
•Increase the concentration of fluoride ions lead to
formation of calcium fluoride and phosphate,
•while the presence of acid leads to break down of the
outer enamel surfaces (hydrolysis of hydroxyapatite and
release of calcium and phosphate) thus formation of
DCPD (dicalcium phosphate dehydrate)
Acidulated phosphate fluoride (APF):

Acidulated phosphate fluoride (APF):

•In both reactions phosphate formed. The
increase in phosphate concentration causes the
shift in the equilibrium of the reaction to right
side that is in the direction of formation of
fluoroapatite as well as hydroxyapatite crystals.
•In another word, the increase in the
concentration of fluoride ions and lowering the
pH in presence of phosphate lead to increase
deposition of ions in form of fluoroapatite
crystals (ie increase fixation of fluoride ions in
the enamel surface).

•Acidulated phosphate (APF) is
composed of NaF to which acid is
added. The concentration of fluoride
is 1.23%, the acid is in form of
orthophosphoric acid the pH is 3.0.
•(Note: APF solution can be prepared
by dissolving 20 gm of NaF in one
liter of 0.1 M phosphoric acid this
known as Brudevold,s solution ).

•APF comes in form of solution, gel and foam, to these
coloring and flavoring agents added.
• It is chemically stable when stored in plastic containers,
and does not cause discoloration to teeth.
•However it can - not be stored in glass containers as
reducing the free F ions.
•Other dis advantage of APF, that the repeated exposure
of teeth with porcelain and composite restoration to it
may cause loss of material and surface roughening with
cosmetic change because of its high acidity.
•The gel is more preferable than solutions as it increase
the time of retention of the materials on the tooth
surface.

•The gelling material is in the form of
carboxy methyl cellulose or
hydroxyethylcellulose.
•Another type of gelling material added
known as thixotropic gel, it is a gel like
material (not a true gel) as under
pressure it behaves like solution and flow
between teeth, at the same time it
became viscous by low pressure thus will
not flow behind the tray to enter the
patient throat.

Stannous fluoride (SnF2)
•It contains cation (stannous) and anion
(fluoride), both react with enamel surface
forming calcium fluoride, stannous
fluoroapatite and hydrated tin oxide.

•These complex agents increase resistance of
enamel to acid dissolutions.
•Caries reduction by SnF2 was reported to be
greater than NaF.
•Stannous fluoride used in form of solutions. It
is available in powder that is prepared by
dissolving appropriate weight in distilled
water.

•For children the recommended
concentration of stannous
fluoride is 8% (dissolve 0.8 mg in
10 ml of distilled water) applied
once a year (Muhler’s technique).
• For adolescents and adults the
recommended concentration is
10 % (dissolve 1 mg of powder in
10 ml distilled water).

Advantages of SnF2
1- Effective in preventing caries, by rapid penetration of
fluoride in deeper layer of enamel thus increase of the
resistance of enamel against acid.
2- Highly insoluble tin- fluoro- phosphate complex act as
a protective layer against acid attack.
3- Re mineralization of initial carious lesion.
4- De sensitization of teeth.
5- Antibacterial, includes both specific antibacterial effect
against cariogenic bacteria, and non- specific effect
against other type of bacteria.
6- Has an additive effect by tin ions in addition to fluoride
ions.

•1- Not stable in aqueous solution, it under goes
rapid hydrolysis and oxidation to form stannous
hydroxide and stannic ions. These may reduce the
effectiveness of fluoride. Thus, stannous fluoride
solution need to be freshly prepared.
•2- Un pleasant taste with metallic astringent taste
and highly acidic (pH 2.1- 2.3).
•3- Reversible irritation to gingival, as gingival
bleaching may occur. It is not recommended to be
used in sever gingival inflammation.
•4- Discoloration of hypo calcified area and staining of
margin of restoration.
Disadvantage

Indication of use:
1- Primary preventive programs (once or twice a
year).
2- High risk group and rampant caries (every 3 or 6
months).
3- Initial caries (3 or 6 months)
4- Desensitizing agents (once a week then every 3
– 6 months)
5- Patients with xerostomia ( 3- 6 months).
6- Patients with hypoplasia or calcifications (as
amelogensis imperfecta or dentionogensis
imperfecta).
7- Root caries.

Fluoridated varnishes
•These are slow release or semi-slow release agents.
• Prolonged exposure time and high fluoride
concentrations result in the formation of a large
calcium fluoride reservoir.
•Fluoride release continues for a long time, as for at
least 8 hours or even for several weeks according
to the type used.
•Studies showed that the use of fluoridated
varnishes resulted in the most significant caries
reduction among topical fluoride agents (30-70%
caries reduction).

Types:
1- Duraphate:
• It contains 5% NaF (2.26% F). It is viscous, resinous varnish. In contact with
saliva, Duraphate hardens into a yellowish brown coating.
2- Fluor protector:
• It is a polyurthan-based varnish contains 0.9% silane fluoride (0.1% F). The
varnish is acidic and hardness in air in to a colorless, transparent film within
2-3 minutes. The silane fluoride, is insoluble in water but reacts on contact
with saliva, releasing small amounts of hydrogen fluoride that penetrates
enamel more rapidly than other types of fluoride.
3- Bifluoride 12:
• Is a clear varnish containing 6% NaF and 6% CaF2, The varnish base consists
of collodion and organic solvents.

Indication of use:
•- high risk group (to be applied 2-4 times /
year).
•- Initial caries even for children under 6 years
of age as can be applied on the affected
surface only.
•- Highly indicated for sensitive teeth.
•- Root caries.
•Varnishes should not be applied in presence of
sever gingival bleeding to prevent the
development contact energy with the
components of the varnishes.

Fluoride containing prophylactic paste
•Before applications of fluoride agents, it
recommends to clean teeth and restoration by
polishing with a rubber cup using pumice, in
order to remove all exogenous deposit.

Different types are available as:
__Zirconium silicate contains stannous fluoride;
__Silicon dioxide contains acidulated phosphate
fluoride.
__This paste is not a substitute for the topical
agents; they are used in order to increase the
accessibility for fluoride ions by tooth surface.
__Thorough prophylaxis will remove a thin layer
of enamel (1 – 4 µm), thus it is always
recommend using F pumice.

Fluoride and restorative material:
•Different restorative material may contain fluoride
to be released slowly to prevent recurrent caries as
glass ionomer cement, resin modified glass
ionomer cement, resin composite, amalgam.
Fluoride may be added also to fissure sealants.
Fluoride release devices:
•Devices allow for a slow release of F ions, as glass
beads, copolymer membrane type and others.
Indicated for patients with high risk group and
those wearing orthodontic appliance.
• Not to be given for a child receiving fluoride
supplements.
•

Fluoride toxicity
•There are two types of toxicity related to
fluoride:
•1- Acute fluoride toxicity due to single
ingestion of a large dose of fluoride at one
time.
•2- Chronic fluoride toxicity due to long term
ingestion of small amount of fluoride for a
long time.

Acute fluoride toxicity:
•It is the rapid excessive ingestion of fluoride at one time,
the speed and severity of ingestion depend on amount of
fluoride ingested and the weight and age of the victim. The
certainly lethal dose (CLD) for adults,
70 Kg weight is 5 – 10 gm F/ Kg body weight.
•For children the CLD is not well known but the probable
toxic dose is
• 5 mg / kg body weight.
•It is always recommended not to dispense more than 264
mg of F at any time.
•Note: the PTD is the threshold dose that trigger immediate
emergency.

General factors affecting acute toxicity:
1- Form of administration:
Fluoride toxicity from solution agents is greater
than others form because of faster absorption of
fluoride ions.
2- Rate of absorption: acidity and empty stomach
in addition to highly soluble agents may increase
the rate of absorption of F ions thus toxicity.
3- Age: toxicity is more among younger children,
also the body weight is an affecting factor, as
increase body weight may have less toxicity.

Signs and symptoms of acute
toxicity:
•GIT; nausea, vomiting, diarrhea, abdominal
pain, and cramps.
•CNS, paresthesia, tetany, CNS depression
and coma.
•CVS; weak pulse, hypotension, pallor, shock,
cardiac irregularities and ultimately failure
•Blood chemistry; acidosis, hypocalcaemia,
hypomagnesaemia.

Emergency treatment depends on the dose ingested:
1- Less than 5 mg/kg body wt.,
- give calcium orally or milk to relive gastro intestinal
symptoms.
- Induce vomiting if necessary
- Keep child under observations.
2- More than 5 mg F/ kg body wt.;
- Empty stomach by induction of vomiting using emetic
materials.
- If vomiting is not possible as for infant or young child or
retarded patient then endotracheal intubation is performed
before gastric lavage.
- Give solution as milk or Ca- gluconate 5% or Ca – lactate
solution.
- Admit to hospital.

3- More than 15 mg / kg.
- Admit to hospital immediately.
- Cardiac monitoring
- IV administration of 10 ml of 10% Ca
gluconate solutions.
- Monitoring of electrolyte especially
Ca and K.
- Adequate urine out- put by diuretic.
- Supportive measures for shock.

Recommendations to avoid toxicity:
1-Use small amount of topical
fluoride agents in the clinic (not
more than 4 ml).
2- Self applied fluoride for children
need to be observed by parents.
3- Keep F supplements out of the
reach of children.

Chronic Fluoride toxicity:
It is long term ingestion of small amount of F for
years, in teeth is dental fluorosis and in bone is
skeletal fluorosis.
Chronic toxicity affecting teeth may lead to dental
fluorosis, while affecting bone may lead to skeletal
fluorosis.
Dental fluorosis:
Dental fluorosis, a hypoplasia tooth enamel or dentin,
ranges in intensity from barely noticeable whitish
striations to confluent pitting and staining.
Various indexes or classification systems have been
used in surveys to measure the presence and severity
of enamel fluorosis.

Dean's classification system has been used most frequently
over the years for assessing fluorosis.

Skeletal fluorosis:
A term used to describe any changes in bone
because of ingestion of at least 8 ppm of fluoride
for years.
Signs:
- More dense bone.
- Diffuse bone.
-Thickening of cortical bone.
-Numerous exostoses. Through- out the
skeleton.
-Calcification of ligaments and tendon
-Crippling fluorosis in severe cases.

The severity of these signs depends on:
1- The duration of fluoride intake.
2- Total amount of fluoride ingested.
3- Concentration of F ingested.
4- Age of the individual.
This condition is seen in polluted area
due to industrial factories or volcanic
actions.