Lec.

6 Prevention Fifth grade

Professionally applied fluoride
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

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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 counselling,
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, 8% stannous fluoride, and acidulated
phosphate fluoride systems 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

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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%, (19,500ppm) 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). As will
be noted later, 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. SnF 2 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 SnF 2, calcium
tri-fluoro stannate gets formed along with tin-tri-fluorophosphate which is render the tooth structure
more stable and less susceptible to caries. Calcium fluoride 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.

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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 (12,300ppm), 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 conventionnal 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. Although
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.

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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 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 contains stannous fluoride.
2. Silicon dioxide contains acidulated phosphate fluoride.

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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 (YbF 3) 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.