OEHS Academy: New and Aspiring Principals Responsibilities
بسم الله الرحمن
الرحيم
صدق الله العلي العظيم
Professionally applied
fluoride
Dr. Rihab Abdul Hussein Ali
B.D.S , M.Sc. , PhD.
•
Studies
of the use of professional topical
fluoride applications (by
dental personnel
) for
the control of dental caries began in the early
1940
s. Since that time, it has been generally
accepted that the fluoride content of
enamel
is
inversely
related to the prevalence of
dental
caries
.
•
Materials used available in form of
solutions
,
gel
,
foam
,
varnishes
,
pumices
,
fluoride
release
devices
and fluoridated
restorative
materials. It
was assumed that it was necessary to administer
a thorough
dental prophylaxis
prior to the
topical application of fluoride.
Indications of use in:
•
Patients at
high risk
of caries on
smooth
surfaces and
root
surfaces.
•
Patients with
rampant
caries.
•
Sensitive
teeth.
•
Non-fluoridated
area.
•
Special
groups like patients with
reduced
salivary flow
rate, patients undergoing
head
and neck irradiation
as well as patients with
orthodontic
treatment.
Professional fluoride-delivery methods
The two most common methods are:
1- Paint-on technique:
The patient instructed to
rinse
the mouth. Teeth are
isolated
using cotton roll
and saliva ejector, the patient position in
upright
and the head
tilted forward
, fluoride material
applied to teeth by
cotton or brush
. The fluoridated
agent applied following dryness of teeth for
1-4
minutes following the manufacturer’s instructions.
The amount of agent used must
not exceed 4ml
to
prevent
acute
toxicity. Used
un waxed
dental floss
to push the material between teeth.
•
After the treatment, the patient should be
asked to
expectorate
several times and
instructed
not eat or drink
for at least
30
minutes. It was found that significantly
greater
fluoride deposition occurred when
the patients were
not
permitted to
rinse, eat,
or drink
following the fluoride treatment.
•
This method is
better
to be used for patient
suffers of
gaging reflex
. It is the
appropriate
method for
gels and solutions
.
2- Tray technique
•
A small amount of fluoride is adding to a
tray
without overloading
, this allow the
flow
of gels
or
foams
to cover the teeth surfaces. The patient
should be seated in
upright
position. The
materials should be
left in place
following the
manufacture instructions. Trays come in different
shapes and types
as custom vinyl.
•
Reports have shown that
10 to 30
mg of fluoride
may be inadvertently
swallowed
during the
application procedure, and the
ingestion
of these
quantities of fluoride by
young children
may
contribute to the development of
dental fluorosis
in
those teeth that are
unerupted
and in the
developmental stage. The
precautions
to reduce the
amount of inadvertently swallowed fluoride to
less
than 2
mg, which may be expected to be of little
consequence.
Application Frequency
•
The frequency of topical applications should be
dictated by the
conditions
and
needs
presented
by each patient. Thus, it is recommended that
new patients, regardless of age, with
active
caries
be given an
initial
series of
four
topical
fluoride applications within a period of
2 to 4
weeks
. If desired, the
initial
application may be
preceded by a
thorough prophylaxis
, the
remaining
three
applications constituting the
initial treatment series should be
preceded
by
tooth
brushing
to remove plaque and oral debris.
•
This series of treatments may be
combined
with the
plaque control
,
dietary counseling
,
and initial
restorative
programs. Then patient
should be given
single
, topical applications at
intervals of
3, 6, or 12
months, depending on
his or her
caries
status. Patients with
little
evidence of
existing
or
anticipated
caries
should be given
single
applications every
12
months as a preventive measure.
•
Three different fluoride systems
have been
adequately evaluated and approved for use
professionally
by dentist. These three systems
are:
•
2%
sodium fluoride system.
•
8%
stannous fluoride system.
•
Acidulated phosphate fluoride system containing
1.23%
fluoride.
Sodium Fluoride (NaF)
•
This material is available in
powder
,
gel
, and
liquid
form. The compound is recommended for
use in a
2%
concentration (=
9200
ppm), which
may be prepared by dissolving
0.2
g of powder in
10
mL of distilled water. The prepared solution
or gel has a
basic pH
and is stable if stored in
plastic
containers. It should
not be store
in a
glass
container, it will react with the
silica
of the
glass forming
silicon dioxide
fluoride
reducing
fluoride anticaries effect.
•
Ready-to-use
2%
solutions and gels of NaF are
commercially
available
; because of the relative
absence of taste
considerations with this
compound, these solutions generally contain
little
flavoring
or
sweetening
agents. This material is
not irritant
to the gingiva, and does
not
cause
discoloration
of teeth. The only
disadvantage
is
requiring
four visits weekly
(
Knutson’s
technique). It is recommended to be applied at ages
3, 7, 11 and 13
years. Coinciding the
eruption
time
of
permanent and primary
teeth.
Mechanism of action:
•
NaF reacts with
hydroxyl apatite
crystals in
enamel
forming
calcium fluoride
. A
thick
layer
formed and interfered with the
further
dissolution
of fluoride from the topical agent. The
CaF
2
formed
reacts
with the hydroxyl apatite
crystals to form
fluoridated hydroxyl
apatite
which in turn makes the tooth surface
resistant
against caries attack.
Ca
10
(PO
4
)
6
(OH)
2
+20F
-
→10CaF
2
+ 6PO
43-
+ 2OH
-
CaF
2
+ 2Ca
5
(PO
4
)
3
OH →2Ca
5
(PO
4
)
3
F+ Ca(OH)
2
Stannous Fluoride (SnF2)
•
This compound is available in
powder
form either
in
bulk
containers or
pre-weighed
capsules. The
recommended and approved concentration is
8%
,
(
19,500
ppm) which is obtained by dissolving
0.8
g
of the powder in
10
mL of distilled water. Stannous
fluoride solutions are quite
acidic
, with a
pH
of
about
2.4 to 2.8
. Aqueous solutions of SnF2 are
not
stable
because of the formation of
stannous
hydroxide
and, subsequently,
stannic oxide
, which
is visible as a
white
precipitate. As a result,
solutions of this compound must be prepared
immediately
prior to use (
Muhlar
technique).
•
SnF2 solutions have a
bitter, metallic
taste. To
eliminate the
need to prepare
this solution from
the
powder
and to
improve
patient
acceptance
,
a
stable, flavored
solution can be prepared with
glycerine and sorbitol
to retard
hydrolysis
of
the SnF2 and with any of a variety of
compatible
flavoring
agents. SnF2 may cause
irritation
to
gingiva
,
pigmentation
around the
margins of
restoration
and
discoloration
of
hypocalcified
regions of the teeth. SnF2 used for
sensitive
teeth
and
effective
in prevention and reduction of
caries
greater
than
sodium fluoride
.
Mechanism of action:
•
SnF2 reacts with
hydroxyl apatite
crystals in
enamel
, the tin of
stannous fluoride
also reacts
with enamel and new crystalline gets formed called
stannous-tri-fluorophosphate
is more
resistant
to
caries.
Tin hydroxyphosphate
(gets
dissolved
in
oral fluids and is responsible for the
metallic
taste)
is formed when SnF2 is applied in
low
concentration. While at
high
concentration of SnF2,
calcium tri-fluoro stannate
gets formed along with
tin-tri-fluorophosphate
which is render the tooth
structure
more stable
and
less susceptible
to caries.
CaF2 is the
end product
in
low
and
high
concentration.
•
The reaction at low concentration is:
Ca5 (PO4)3OH + 2SnF2 → 2CaF2 + Sn2(OH)
PO4
+
Ca3(PO4)2
•
The reaction at high concentration is:
Ca5 (PO4)3OH + 16SnF2 → CaF2 +
2SnF3F3PO4 (
Tin-tri-fluorophosphate
)+
Sn2(OH)PO4 (Tin hydroxyphosphate)+
4CaF2(SnF3)2 (
Calcium tri-fluoro stannate
)
2Ca5 (PO4)3OH + CaF2 → 2 Ca5(PO4)3F + Ca(OH)2
•
There are two ways of speeding the reactions
and lead to formation of fluoroapetite.
1.
Increase
the
concentration
of fluoride ions in the
agents.
2.
Lowering
the
pH
that is making the solution more
acidic
.
•
The success of any topical fluoridated agent
depend on it is capability of depositing fluoride
ions in the enamel as
fluoroapetite
and
not on
only calcium fluoride
.
Acidulated Phosphate Fluoride (APF)
•
This treatment system is available as either a
solution or gel
, both of which are
stable
and
ready to use
. Both forms contain
1.23
% fluoride
(
12,300
ppm), generally obtained by the use of
2.0
% sodium fluoride and
0.34
%
hydrofluoric
acid
. Phosphate is usually provided as
orthophosphoric
acid in a concentration of
0.98
%.
The pH of true APF systems should be
about
3.5
.
•
Gel preparations feature a
greater variation
in
composition
, particularly with regard to the
source
and
concentration
of phosphate. In
addition, the gel preparations generally contain
thickening
(binders),
flavoring
, and
coloring
agents. The
gelling
agent is in form of
methylcellulose
or
hydroxyethyl cellulose
is
added to solution and the pH is
4-5
. The
Brudevold’s
solution prepared by dissolving
20
gm of
sodium fluoride
in
1
liter of
0.1
M
phosphoric acid
.
•
Another
form of acidulated phosphate fluoride
for topical applications called
thixotropic gels
.
The term thixotropic denotes a
solution
that sets
in a
gel-like
state but is
not
a
true gel
. On the
application of
pressure
, thixotropic gels behave
like solutions
; it has been suggested that these
preparations are
more easily
forced into the
interproximal spaces
than conventional gels.
The
active
fluoride system in thixotropic gels is
identical
to conventional APF solutions. To help
prevent ingestion
it is recommended that the
patient sits
upright
and does
not swallow
.
•
No more
than
2.5
ml of gel per tray should be
applied, and
custom
or properly
fitted stock trays
with absorptive liners should be used.
Suction
devices should be used during and after treatment
and
excess gel
removed with
gauze
. Patients
should
spit out
thoroughly after treatment.
•
The
gels
are usually recommended to be used
twice
yearly, but when
more severe
caries is
present they may be used
more frequently
. A
significant reductions in caries incidence have been
achieved using these products.
•
Within the past few years, a
foam
form of APF has
become
available
. The primary
advantage
of
foam preparations is that appreciably
less material
is used for a treatment and therefore
lesser
amounts
are likely to be inadvertently
swallowed
by young children during the professional
application.
•
AFP is
stable in plastic
container and
not
staining
the teeth.
Repeated
exposure of
porcelain or composite
restoration to AFP can
lead to
loss of material
and
roughening
because
of its
high acidity
.
Mechanism of action:
•
AFP applied on teeth leads to
dehydration
and
shrinkage
in the
volume
of hydroxyapatite
crystals which forms
dicalcium phosphate
dihydrate
(
DCPD
)(Ca HPO
4
2H
2
O). Fluoride
penetrates
deeply
and leads to formation of
fluorapatite (
FA
)( Ca
5
(PO
4
)
3
F). When
acidic
fluoride at
high
concentrations is applied to the
tooth surface
calcium
is ‘
etched
’ from the
surface of the tooth. The
free calcium
that is
released
, and calcium that is present in
saliva
,
react with the
fluoride ions
present in the topical
fluoride to form
calcium fluoride
.
•
When the
saliva
returns the plaque
pH
to
neutral
, the calcium fluoride precipitates
and deposits as
tiny granules
of
insoluble
fluoride that occupy the
etched areas
. Later,
when a
cariogenic
food is consumed and
lactic acid
is produced by plaque, the
pH
drops
and the calcium fluoride ‘spheres’
dissolve
,
releasing
fluoride ions
locally
.
Varnishes
•
Fluoride varnishes have been used in
dental office
and community
programs
since
1960
s. They are
generally used to provide fluoride at
risk sites or
surfaces
within the mouth and are usually applied
at intervals of
3 or 6
months. They contain
high
levels of fluoride and are designed to
harden
on
the tooth to
aid retention
. Varnishes have been
shown to
work as well as gels
, and the varnishes
are
preferred
because
less
fluoride is
ingested
.
•
Teeth should be relatively
dry
before applying
fluoride varnish. The
paint brush
that comes with
the product is used to paint the varnish on
all
selected
tooth surfaces. Patients should be
instructed that some varnishes leave a
temporary,
yellow stain
that can last for
24
hours. Varnishes
are highly indicated for
sensitive
teeth and for
children
under 6
years old that can be applied on
the
affected surface only
. While it is
contraindicated
in patients with
gingivitis
.
•
The most widely used is
Duraphat
varnish, containing
5
% sodium fluoride (
22,600
ppm F) that
sets on contact
with saliva
. Patients are instructed
not to eat
within
two
hours. Duraphat usually remains on the tooth surfaces for
about
24
hours. It is believed that delivery of
high doses
of fluoride of this type results in the
local formation
of
calcium fluoride, which can act as a
reservoir
for the
slow
release
of fluoride.
•
Fluor protector
varnish is
polyurethane-based
varnish
0.9
wt %
silane fluoride
. The varnish is
acidic
and
hardened in air
into
colorless
within
2-3
minutes. It is
retained on the teeth for
1-2
weeks.
•
Another type is
Bifluoride 12
varnish
contains
6% NaF
and
6% CaF
. It is retained on the tooth surfaces
for days
and it used also for treatment of
hypersensitive exposed
root dentin
.
Slow-release fluoride devices
•
An
optimum
fluoride-delivery system would be
one that supplies
small amounts
of fluoride
throughout the
day
so that
consistent, elevated
plaque fluoride
levels are maintained with
little
or no
individual effort required. To be effective
the fluoride
release has to be
constant
and
sustained
and the ‘device’ must be
retained
in
the mouth
without
causing
damage
to soft
tissues or becoming loose.
•
Materials used are (
plastic or glass beads
containing fluoride
), the
copolymer
membrane
type and recently used a
mixture
of
NaF
and
hydroxyapatite
.
Slow-release glass materials retained on
the
buccal
surface of
molar
teeth have
shown
effectiveness
, and
bioadhesive
tablets
and other systems have also been
evaluated.
Fluoridated prophylactic paste
•
Before application of fluoride agents, it is recommended to
clean
teeth and
polishing
with
rubber cup using pumice
.
•
Different types of Fluoridated prophylactic paste are
available as:
1.
Zirconium silicate
contadins
stannous fluoride
.
2.
Silicon dioxide
contains
acidulated phosphate fluoride
.
•
These pastes are
not
a substitute for the
topical agents
,
they are used in order to
increase
the accessibility of
fluoride ions in tooth surface.
Polishing
will remove a
thin
layer
of enamel (
1-4μm
), thus it is always recommended
using
F pumice
to
replenish
the minerals that
abraded
during polishing.
Restorative materials containing fluoride
•
An alternative approach is to use
dental materials
to provide fluoride delivery. It is important that
addition
of fluoride does
not compromise
the
required properties
of the restorative material.
•
Materials such as the old
silicate restorative
materials and
glass-ionomer cements
contain
between
15 and 20
% fluoride, and
resin modified
glass ionomers
,
polyacid-modified composite
resin
(
compomers
),
fissure sealants,
fluoride has
also been added to
other
dental materials such as
composite and amalgam
.
•
While Fluoride releasing materials include the
addition
of
ytterbium fluoride
(YbF3) to
commercial glass-ionomer
cement,
organic
fluorides in the form of
amine fluorides
(AmF).
•
These materials could potentially provide a
fluoride reservoir
to help prevent
secondary
caries
and to prevent or help
remineralize
caries
in
adjacent teeth
or
surfaces
. These materials
may feature greater
longevity
, a
reduced
incidence of
marginal failure
, an
elevated
concentration
of fluoride in
plaque
, together
with an
antibacterial
action when compared with
non-fluoride releasing materials.
•
In addition, fluoride-releasing materials may
perform
better
in caries
inhibition
in
artificial
caries model
studies than non-fluoridated materials.
•
Initially, fluoride release from most methods tends
to be
high
, but it
reduces
as the available
reservoir
depletes
. Nevertheless, even
1
year after application
of a
glass-ionomer cement
fluoride levels were
six
times higher
than normal in
unstimulated
saliva. It
is believed that glass ionomer cements may act as a
reservoir
by
absorbing fluoride
from other
sources such as
toothpaste
and
slowly releasing
this as fluoride levels
diminish
in the oral cavity.
Recommendations for fluoride-delivery methods
1- Fluoride is
topically available
in the oral cavity
at
concentrations
that can significantly affect the
ongoing
de- mineralization
and
remineralization
process
2-
Ingestion
of fluoride is
minimized
.
3- The
method
of delivery is
cost-effective
.
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Presentation Transcript
Professionally applied fluoride Dr. Rihab Abdul Hussein Ali B.D.S , M.Sc. , PhD.
Studies of the use of professional topical fluoride applications (by dental personnel) for the control of dental caries began in the early 1940s. Since that time, it has been generally accepted that the fluoride content of enamel is inversely related to the prevalence of dental caries. Materials used available in form of solutions, gel, foam, varnishes, pumices, fluoride release devices and fluoridated restorative materials. It was assumed that it was necessary to administer a thorough dental prophylaxis prior to the topical application of fluoride.
Indications of use in: Patients at high risk of caries on smooth surfaces and root surfaces. Patients with rampant caries. Sensitive teeth. Non-fluoridated area. Special groups like patients with reduced salivary flow rate, patients undergoing head and neck irradiation as well as patients with orthodontic treatment.
Professional fluoride-delivery methods The two most common methods are: 1- Paint-on technique: The patient instructed to rinse the mouth. Teeth are isolated using cotton roll and saliva ejector, the patient position in upright and the head tilted forward, fluoride material applied to teeth by cotton or brush. The fluoridated agent applied following dryness of teeth for 1-4 minutes following the manufacturer s instructions. The amount of agent used must not exceed 4ml to prevent acute toxicity. Used un waxed dental floss to push the material between teeth.
After the treatment, the patient should be asked to expectorate several times and instructed not eat or drink for at least 30 minutes. It was found that significantly greater fluoride deposition occurred when the patients were not permitted to rinse, eat, or drink following the fluoride treatment. This method is better to be used for patient suffers of gaging reflex. It is the appropriate method for gels and solutions.
2- Tray technique A small amount of fluoride is adding to a tray without overloading, this allow the flow of gels or foams to cover the teeth surfaces. The patient should be seated in upright position. The materials should be left in place following the manufacture instructions. Trays come in different shapes and types as custom vinyl.
Reports have shown that 10 to 30 mg of fluoride may be inadvertently swallowed during the application procedure, and the ingestion of these quantities of fluoride by young children may contribute to the development of dental fluorosis in those teeth that are unerupted and in the developmental stage. The precautions to reduce the amount of inadvertently swallowed fluoride to less than 2 mg, which may be expected to be of little consequence.
Application Frequency The frequency of topical applications should be dictated by the conditions and needs presented by each patient. Thus, it is recommended that new patients, regardless of age, with active caries be given an initial series of four topical fluoride applications within a period of 2 to 4 weeks. If desired, the initial application may be preceded by a thorough prophylaxis, the remaining three applications constituting the initial treatment series should be preceded by tooth brushing to remove plaque and oral debris.
This series of treatments may be combined with the plaque control, dietary counseling, and initial restorative programs. Then patient should be given single, topical applications at intervals of 3, 6, or 12 months, depending on his or her caries status. Patients with little evidence of existing or anticipated caries should be given single applications every 12 months as a preventive measure.
Three different fluoride systems have been adequately evaluated and approved for use professionally by dentist. These three systems are: 2% sodium fluoride system. 8% stannous fluoride system. Acidulated phosphate fluoride system containing 1.23% fluoride.
Sodium Fluoride (NaF) This material is available in powder, gel, and liquid form. The compound is recommended for use in a 2% concentration (= 9200 ppm), which may be prepared by dissolving 0.2 g of powder in 10 mL of distilled water. The prepared solution or gel has a basic pH and is stable if stored in plastic containers. It should not be store in a glass container, it will react with the silica of the glass forming silicon dioxide fluoride reducing fluoride anticaries effect.
Ready-to-use 2% solutions and gels of NaF are commercially available; because of the relative absence of taste considerations with this compound, these solutions generally contain little flavoring or sweetening agents. This material is not irritant to the gingiva, and does not cause discoloration of teeth. The only disadvantage is requiring four visits weekly (Knutson s technique). It is recommended to be applied at ages 3, 7, 11 and 13 years. Coinciding the eruption time of permanent and primary teeth.
Mechanism of action: NaF reacts with hydroxyl apatite crystals in enamel forming calcium fluoride. A thick layer formed and interfered with the further dissolution of fluoride from the topical agent. The CaF2 formed reacts with the hydroxyl apatite crystals to form fluoridated hydroxyl apatite which in turn makes the tooth surface resistant against caries attack. Ca10 (PO4)6(OH)2 +20F- 10CaF2+ 6PO43-+ 2OH- CaF2+ 2Ca5 (PO4)3OH 2Ca5 (PO4)3 F+ Ca(OH)2
Stannous Fluoride (SnF2) This compound is available in powder form either in bulk containers or pre-weighed capsules. The recommended and approved concentration is 8%, (19,500 ppm) which is obtained by dissolving 0.8 g of the powder in 10 mL of distilled water. Stannous fluoride solutions are quite acidic, with a pH of about 2.4 to 2.8. Aqueous solutions of SnF2 are not stable because of the formation of stannous hydroxide and, subsequently, stannic oxide, which is visible as a white precipitate. As a result, solutions of this compound must be prepared immediately prior to use (Muhlar technique).
SnF2 solutions have a bitter, metallic taste. To eliminate the need to prepare this solution from the powder and to improve patient acceptance, a stable, flavored solution can be prepared with glycerine and sorbitol to retard hydrolysis of the SnF2 and with any of a variety of compatible flavoring agents. SnF2 may cause irritation to gingiva, pigmentation around the margins of restoration and discoloration of hypocalcified regions of the teeth. SnF2 used for sensitive teeth and effective in prevention and reduction of caries greater than sodium fluoride.
Mechanism of action: SnF2 reacts with hydroxyl apatite crystals in enamel, the tin of stannous fluoride also reacts with enamel and new crystalline gets formed called stannous-tri-fluorophosphate is more resistant to caries. Tin hydroxyphosphate (gets dissolved in oral fluids and is responsible for the metallic taste) is formed when SnF2 is applied in low concentration. While at high concentration of SnF2, calcium tri-fluoro stannate gets formed along with tin-tri-fluorophosphate which is render the tooth structure more stable and less susceptible to caries. CaF2 is the end product in low and high concentration.
The reaction at low concentration is: Ca5 (PO4)3OH + 2SnF2 2CaF2 + Sn2(OH) PO4 + Ca3(PO4)2 The reaction at high concentration is: Ca5 (PO4)3OH + 16SnF2 CaF2 + 2SnF3F3PO4 (Tin-tri-fluorophosphate)+ Sn2(OH)PO4 (Tin hydroxyphosphate)+ 4CaF2(SnF3)2 (Calcium tri-fluoro stannate) 2Ca5 (PO4)3OH + CaF2 2 Ca5(PO4)3F + Ca(OH)2
There are two ways of speeding the reactions and lead to formation of fluoroapetite. 1. Increase the concentration of fluoride ions in the agents. 2. Lowering the pH that is making the solution more acidic. The success of any topical fluoridated agent depend on it is capability of depositing fluoride ions in the enamel as fluoroapetite and not on only calcium fluoride.
Acidulated Phosphate Fluoride (APF) This treatment system is available as either a solution or gel, both of which are stable and ready to use. Both forms contain 1.23% fluoride (12,300 ppm), generally obtained by the use of 2.0% sodium fluoride and 0.34% hydrofluoric acid. Phosphate is usually provided as orthophosphoric acid in a concentration of 0.98%. The pH of true APF systems should be about 3.5.
Gel preparations feature a greater variation in composition, particularly with regard to the source and concentration of phosphate. In addition, the gel preparations generally contain thickening (binders), flavoring, and coloring agents. The gelling agent is in form of methylcellulose or hydroxyethyl cellulose is added to solution and the pH is 4-5. The Brudevold s solution prepared by dissolving 20 gm of sodium fluoride in 1 liter of 0.1M phosphoric acid.
Another form of acidulated phosphate fluoride for topical applications called thixotropic gels. The term thixotropic denotes a solution that sets in a gel-like state but is not a true gel. On the application of pressure, thixotropic gels behave like solutions; it has been suggested that these preparations are more easily forced into the interproximal spaces than conventional gels. The active fluoride system in thixotropic gels is identical to conventional APF solutions. To help prevent ingestion it is recommended that the patient sits upright and does not swallow.
No more than 2.5 ml of gel per tray should be applied, and custom or properly fitted stock trays with absorptive liners should be used. Suction devices should be used during and after treatment and excess gel removed with gauze. Patients should spit out thoroughly after treatment. The gels are usually recommended to be used twice yearly, but when more severe caries is present they may be used more frequently. A significant reductions in caries incidence have been achieved using these products.
Within the past few years, a foam form of APF has become available. The primary advantage of foam preparations is that appreciably less material is used for a treatment and therefore lesser amounts are likely to be inadvertently swallowed by young children during the professional application. AFP is stable in plastic container and not staining the teeth. Repeated exposure of porcelain or composite restoration to AFP can lead to loss of material and roughening because of its high acidity.
Mechanism of action: AFP applied on teeth leads to dehydration and shrinkage in the volume of hydroxyapatite crystals which forms dicalcium phosphate dihydrate (DCPD)(Ca HPO4 2H2O). Fluoride penetrates deeply and leads to formation of fluorapatite (FA)( Ca5(PO4)3F). When acidic fluoride at high concentrations is applied to the tooth surface calcium is etched from the surface of the tooth. The free calcium that is released, and calcium that is present in saliva, react with the fluoride ions present in the topical fluoride to form calcium fluoride.
When the saliva returns the plaque pH to neutral, the calcium fluoride precipitates and deposits as tiny granules of insoluble fluoride that occupy the etched areas. Later, when a cariogenic food is consumed and lactic acid is produced by plaque, the pH drops and the calcium fluoride spheres dissolve, releasing fluoride ions locally.
Varnishes Fluoride varnishes have been used in dental office and community programs since 1960s. They are generally used to provide fluoride at risk sites or surfaces within the mouth and are usually applied at intervals of 3 or 6 months. They contain high levels of fluoride and are designed to harden on the tooth to aid retention. Varnishes have been shown to work as well as gels, and the varnishes are preferred because less fluoride is ingested.
Teeth should be relatively dry before applying fluoride varnish. The paint brush that comes with the product is used to paint the varnish on all selected tooth surfaces. Patients should be instructed that some varnishes leave a temporary, yellow stain that can last for 24 hours. Varnishes are highly indicated for sensitive teeth and for children under 6 years old that can be applied on the affected surface only. While it is contraindicated in patients with gingivitis.
The most widely used is Duraphat varnish, containing 5% sodium fluoride (22,600 ppm F) that sets on contact with saliva. Patients are instructed not to eat within two hours. Duraphat usually remains on the tooth surfaces for about 24 hours. It is believed that delivery of high doses of fluoride of this type results in the local formation of calcium fluoride, which can act as a reservoir for the slow release of fluoride. Fluor protector varnish is polyurethane-based varnish 0.9 wt % silane fluoride. The varnish is acidic and hardened in air into colorless within 2-3 minutes. It is retained on the teeth for 1-2 weeks. Another type is Bifluoride 12 varnishcontains 6% NaF and 6% CaF. It is retained on the tooth surfaces for days and it used also for treatment of hypersensitive exposed root dentin.
Slow-release fluoride devices An optimum fluoride-delivery system would be one that supplies small amounts of fluoride throughout the day so that consistent, elevated plaque fluoride levels are maintained with little or no individual effort required. To be effective the fluoride release has to be constant and sustainedand the device must be retained in the mouth without causing damage to soft tissues or becoming loose.
Materials used are (plastic or glass beads containing fluoride), the copolymer membrane type and recently used a mixture of NaF and hydroxyapatite. Slow-release glass materials retained on the buccal surface of molar teeth have shown effectiveness, and bioadhesive tablets and other systems have also been evaluated.
Fluoridated prophylactic paste Before application of fluoride agents, it is recommended to clean teeth and polishing with rubber cup using pumice. Different types of Fluoridated prophylactic paste are available as: 1. Zirconium silicate contadins stannous fluoride. 2. Silicon dioxide contains acidulated phosphate fluoride. These pastes are not a substitute for the topical agents, they are used in order to increase the accessibility of fluoride ions in tooth surface. Polishing will remove a thin layer of enamel (1-4 m), thus it is always recommended using F pumice to replenish the minerals that abraded during polishing.
Restorative materials containing fluoride An alternative approach is to use dental materials to provide fluoride delivery. It is important that addition of fluoride does not compromise the required properties of the restorative material. Materials such as the old silicate restorative materials and glass-ionomer cements contain between 15 and 20% fluoride, and resin modified glass ionomers, polyacid-modified composite resin (compomers), fissure sealants, fluoride has also been added to other dental materials such as composite and amalgam.
While Fluoride releasing materials include the addition of ytterbium fluoride (YbF3) to commercial glass-ionomer cement, organic fluorides in the form of amine fluorides (AmF). These materials could potentially provide a fluoride reservoir to help prevent secondary caries and to prevent or help remineralize caries in adjacent teeth or surfaces. These materials may feature greater longevity, a reduced incidence of marginal failure, an elevated concentration of fluoride in plaque, together with an antibacterial action when compared with non-fluoride releasing materials.
In addition, fluoride-releasing materials may perform better in caries inhibition in artificial caries model studies than non-fluoridated materials. Initially, fluoride release from most methods tends to be high, but it reduces as the available reservoir depletes. Nevertheless, even 1 year after application of a glass-ionomer cement fluoride levels were six times higher than normal in unstimulated saliva. It is believed that glass ionomer cements may act as a reservoir by absorbing fluoride from other sources such as toothpaste and slowly releasing this as fluoride levels diminish in the oral cavity.
Recommendations for fluoride-delivery methods 1- Fluoride is topically available in the oral cavity at concentrations that can significantly affect the ongoing de- mineralization and remineralization process 2- Ingestion of fluoride is minimized. 3- The method of delivery is cost-effective.
