Fluoride therapy is the delivery of fluoride to the teeth topically or systemically in order to prevent tooth decay (dental caries) which results in cavities. Most commonly, fluoride is applied topically to the teeth using gels, varnishes, toothpaste/dentifrices or mouth rinse. Systemic delivery involves fluoride supplementation using water, salt, tablets or drops which are swallowed. Tablets or drops are rarely used where public water supplies are fluoridated.
Benefits
Fluoride therapy is commonly practiced and generally agreed upon as being useful by dentists. Fluoride combats the formation of tooth decay primarily in three ways:
- Fluoride promotes the remineralization of teeth, by enhancing the tooth remineralization process. Fluoride found in saliva will absorb into the surface of a tooth where demineralization has occurred. The presence of this fluoride in turn attracts other minerals (such as calcium), thus resulting in the formation of new tooth mineral.
- Fluoride can make a tooth more resistant to the formation of tooth decay. The new tooth mineral that is created by the remineralization process in the presence of fluoride is actually a "harder" mineral compound than existed when the tooth initially formed. Teeth are generally composed of hydroxyapatite and carbonated hydroxyapatite. Fluorapatite is created during the remineralization process when fluoride is present and is more resistant to dissolution by acids (demineralization).
- Fluoride can inhibit oral bacteria's ability to create acids. Fluoride decreases the rate at which the bacteria that live in dental plaque can produce acid by disrupting the bacteria and its ability to metabolize sugars. The less sugar the bacteria can consume, the less acidic waste which will be produced and participate in the demineralization process.
There are many different types of fluoride therapies, which include at-home therapies and professionally applied topical fluorides (PATF). At-home therapies can be further divided into over-the-counter (OTC) and prescription strengths. The fluoride therapies, whether OTC or PATF, are categorized by application – dentifrices, mouthrinses, gels/ foams, varnishes, dietary fluoride supplements, and water fluoridation.
Mechanism
All fluoridation methods create low levels of fluoride ions in saliva and plaque fluid, thus exerting a topical effect. The fluoride ions reduce the rate of tooth enamel demineralization, and increase the rate of remineralization of the early stages of cavities. Fluoride exerts its major effect by this demineralization and remineralization cycle. Fluoride also affects the physiology of dental bacteria, although its effect on bacterial growth does not seem to be relevant to cavity prevention. Fluoride has minimal effect on cavities after it is swallowed. Technically, fluoride does not prevent cavities but rather controls the rate at which they develop. Although fluoride is the only well-documented agent with this property, it has been suggested that also adding some calcium to the water would reduce cavities further.
Delivery
Water fluoridation
Water fluoridation is the controlled addition of fluoride to a public water supply in order to reduce tooth decay. Its use in the U.S. began in the 1940s, following studies of children in a region where water is naturally fluoridated. It is now used for about two-thirds of the U.S. population on public water systems and for about 5.7% of people worldwide. Although the best available evidence shows no association with adverse effects other than fluorosis, most of which is mild, water fluoridation has been contentious for ethical, safety, and efficacy reasons, and opposition to water fluoridation exists despite its support by public health organizations.
Toothpaste
Most toothpaste today contains 0.1% (1000 ppm) fluoride, usually in the form of sodium fluoride or sodium monofluorophosphate (MFP); 100 g of toothpaste containing 0.76 g MFP equates to 0.1 g fluoride. Toothpaste may cause or exacerbate perioral dermatitis most likely caused by sodium lauryl sulfate, an ingredient in toothpaste. It is suspected that SLS is linked to a number of skin issues such as dermatitis and it is commonly used in research laboratories as the standard skin irritant with which other substances are compared.
Prescription strength fluoride toothpaste generally contains 1.1% (4,950 ppm) sodium fluoride toothpaste. This type of toothpaste is used in the same manner as regular toothpaste. It is well established that 1.1% sodium fluoride is safe and effective as a caries preventive. This prescription dental cream is used once daily in place of regular toothpaste.
Mouth rinses
The most common fluoride compound used in mouth rinse is sodium fluoride. Over-the-counter solutions of 0.05% sodium fluoride (225 ppm fluoride) for daily rinsing are available for use. Fluoride at this concentration is not strong enough for people at high risk for caries.
Prescription mouth rinses are more effective for those at high risk for caries, but are usually counterindicated for children, especially in areas with fluoridated drinking water. However, in areas without fluoridated drinking water, these rinses are sometimes prescribed for children.
Gels/foams
Gels and foams are used for individuals who are at high risk for caries, orthodontic patients, patients undergoing head and neck radiation, patients with decreased salivary flow, and children whose permanent molars should, but cannot, be sealed.
The gel or foam is applied through the use of a mouth tray, which contains the product. The tray is held in the mouth by biting. Application generally takes about four minutes, and patients should not rinse, eat, smoke, or drink for at least 30 minutes after application.
Some gels are made for home application, and are used in a manner similar to toothpaste. The concentration of fluoride in these gels is much lower than professional products.
Varnish
Fluoride varnish has practical advantages over gels in ease of application, a non-offensive taste, and use of smaller amounts of fluoride than required for gel applications. Varnish is intended for the same group of patients as the gels and foams. There is also no published evidence as of yet that indicates that professionally applied fluoride varnish is a risk factor for enamel fluorosis. The varnish is applied with a brush and sets within seconds.
Slow-release devices
Devices that slowly release fluoride can be implanted on the surface of a tooth, typically on the side of a molar where it is not visible and does not interfere with eating. The two main types are copolymer membrane and glass bead. These devices are effective in raising fluoride concentrations and in preventing cavities, but they have problems with retention rates, that is, the devices fall off too often.
Dietary supplements
Dietary fluoride supplements in the form of tablets, lozenges, or liquids (including fluoride-vitamin preparations) are used primarily for children in areas without fluoridated drinking water. The evidence supporting the effectiveness of this treatment for primary teeth is weak. The supplements prevent cavities in permanent teeth. A significant side effect is mild to moderate dental fluorosis.
Indications for fluoride therapy
Depending on the individual's risk factors and the reason for treatment will determine which method of fluoride delivery is used. Consult with a dentist before starting any treatment.
- white spots
- Moderate to high risk patients for developing decay
- Active decay
- Orthodontic treatment
- Additional protection if necessary for children in areas without fluoridated drinking water
- To reduce tooth sensitivity
- Protect root surface
- Decreased salivary flow
- Institutionalized patients
Health risks
There are several risks involved if unusually high amounts of fluoride are consumed. Acute overdose can cause fluoride poisoning and death. Chronic intake and topical exposure may cause dental fluorosis, and excess systematic exposure can lead to systemic effects such as skeletal fluorosis. Young children are at risk for receiving excess fluoride, and the ADA has recently issued an interim guidance on their fluoride consumption.
Overdose
In 1974 a 3-year old child swallowed 45 milliliters of 2% fluoride solution, estimated to be triple the fatal amount, and then died. The fluoride was administered during his first visit to the dentist, and the dental office was later found liable for the death.
Fluorosis
Most fluorosis is mild and cosmetic, but the chance of more severe fluorosis increases with exposure. A recent report by National Research Council (NRC) states that severe dental fluorosis can be considered a "toxic effect" which increases the prevalence of caries (106), but fluorosis this severe is not expected with the normal use of fluoride therapy.
Fluoride conversion chart
| APF (10)(%)(1000) | ppm |
|---|---|
| 1.1% | 10,000 |
| 1.23% | 12,300 |
| NaF (4.5)(%)(1000) | ppm |
| 0.05% | 225 |
| 0.20% | 900 |
| 0.44% | 1,980 |
| 1.0 % | 4,500 |
| 1.1% | 4,950 |
| 2.0% | 9,000 |
| 5.0% | 22,500 |
| SnF2 (2.4)(%)(1000) | ppm |
| 0.40% | 960 |
| 0.63% | 1,512 |
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