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The fluoride decision

April 1, 2001
Age and the patient's choice influence fluoride selection, but what's your choice?

It's true. Our children have been blessed with the benefits of fluoride since birth. They have fewer cavities than any American generation in recorded history. They can start on fluoride drops as infants, vitamin/fluoride tablets as toddlers, and graduate to gels, foams, pastes, and lozenges as they get older. With all the new fluoride products and delivery systems depicted in our dental catalogs, how are we supposed to choose the right ones for our patients?

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The best way to be sure about your product choice is to check out the research. Many products make claims that set them apart from others ... more effective, less expensive, stronger, faster, tastier, etc. Our job as clinicians is to see through the hype and ask, "Where's the proof?"

Proof comes from clinical studies that are controlled, randomized, and double-blind. The results of these tests help us make informed decisions about the product's efficacy. The more long-term the test, the more credible the results. If we check the research in our journals, study clubs, and elsewhere, we can determine which fluoride and method of application is best for our patients.

The three leading fluorides used semiannually in dental offices are:

  • 1.23 percent acidulated phosphate (APF)
  • 2 percent sodium phosphate
  • 8 percent stannous fluoride

The American Dental Association (ADA) and Food and Drug Administration (FDA) recognizes these fluorides for their effectiveness when used in a tray application. But is being effective against dental caries enough? Eight percent stannous fluoride is effective against caries. It also has side effects such as staining of the teeth, sloughing of the gingiva, and a bitter taste to the tongue. Its chemical instability, along with these other drawbacks, keeps it from being more popular.

The most widely used fluoride in dental practices today is APF. Evidence-based research shows that the low 4.0 pH enhances fluoride absorption and is very effective against caries. But hygienists can't just be satisfied with any APF. If the pH level exceeds 4.0, the amount of fluoride uptake is decreased; pH testing has shown that, at 4.5, the enamel-fluoride uptake of APF is only 2,302 ppm compared to 10,000 ppm at pH 3.1. Check the pH level on all APF products to determine their uptake levels. If no pH level is listed on the packaging, find a different APF product that lists the level. As you can see, a pH rise of just .5 over the max of 4.0 makes a big difference!

Because of the concern about etching of composite and porcelain restorations with the constant use of APF (pH 3.0) and stannous fluoride (pH 2.1 to 2.3), these are usually replaced with neutral pH sodium fluoride. In 1981, researchers proved that APF caused pitting in composite resin restorations. Then in 1994, a study showed that APF also pitted resin-veneering material. The same study proved pitting occurred with a 0.4 percent stannous fluoride gel. Neutral sodium fluoride is recommended for patients who present with these restorative materials. But to report on the comparative effectiveness of sodium fluoride against caries, further research is necessary.

In 1993, 1.23 percent APF and 2 percent sodium fluoride foam hit the market. The new application system offered some distinct advantages. The concentration of the foam is the same as the gel, but 75 percent less fluoride is needed because of the consistency. This lessens the risk of a toxic amount being accidentally swallowed. And yet research shows that with the foam, the same amount of fluoride is delivered as with the APF gel.

'Off-label' varnishes

Another form of topical fluoride application is fluoride varnish. In 1964, a varnish containing fluoride was introduced in Germany under the trade name Duraphat. Although the varnish has been tested - providing evidence-based proof of efficacy as an anticaries agent in Europe for more than three decades - it has not yet been approved for use in the United States in this capacity.

However, in 1991, the ADA approved Duraflor for use as a desensitizing agent. In 1997, the FDA approved Duraphat, a 5 percent sodium fluoride varnish, for alleviating hypersensitivity. The FDA approved FluoroProtector, another fluoride varnish, for desensitizing only. The FDA considers fluoride varnishes to fall into the category of devices that "present minimal risk and is/are subject to the lowest level of regulation."

Still, because European researchers compared the varnish to no treatment instead of a placebo, the FDA will not accept the comprehensive European findings as adequate for approval of labeling varnishes as caries preventive agents. The FDA ruled that if the varnish is used for caries prevention, it is a drug. Unfortunately, to support the studies needed for approval of varnishes as therapeutic agents, an interested company would have to spend approximately half a million dollars. This is why many dental offices are using varnishes "off-label" in their practices. As an American Academy of Pediatric Dentistry committee asserted in a 1996 recommendation, "Unapproved does not imply an illegal use. The word unapproved is used merely to indicate lack of approval, not to imply disapproval or contraindication based on positive evidence of a lack of safety or efficacy."

Fluoride varnish is easily applied to exposed root surfaces, and it prolongs contact time between fluoride and teeth, thereby achieving deeper fluoride uptake. The benefits of fluoride varnishes also include long-term fluoride release and a higher delivery of fluoride into cementum.

Dr. Timothy Wright, professor of pediatric dentistry at the University of North Carolina, said that at least four fluoride varnishes are available in the United States. He said, "None of them have ADA or FDA approval as a topical fluoride treatment; however, they are gaining popularity for this application. They have been used in Europe for decades, and there are many studies showing they are clinically as effective, if not more so, than APF treatments, depending on the varnish and study."

Dr. Wright said age and the child's choice influence decisions on whether to use varnish or APF treatments. "We only use varnish for children under five or six years of age, because it produces a much lower serum uptake from the topical treatment and thus is considered safer. It is inappropriate to use APF gel/tray treatments with very young children because they will consume too much fluoride. The varnish sets as a film on contact with moisture and is not washed off the teeth if placed properly. Therefore, a waiting period for eating or drinking is not necessary. We recommend no crunchy foods or brushing for 24 hours after placement. The cost to treat a child with a full primary dentition using a varnish such as Duraphat would be about 50 to 75 cents."

Not everyone jumps on the varnish bandwagon. Lynn Tolle-Watts, BSDH, MS, professor and clinical director of the School of Dental Hygiene at Old Dominion University in Norfolk, Va., said, "I support the use of Duraphat as a desensitizing agent. I do not feel comfortable using any product off-label. Here at ODU we still use the tried-and-true fluoride methods."

In April 2000, a University of Florida study showed that sodium fluoride varnish - with a higher concentration of fluoride than gels, foams and pastes - is at the same time less toxic to children since less of the product is swallowed. Dr. Jaana Autio, an assistant professor of pediatric dentistry at the university, is said to be the first to conduct a study on the effects of fluoride varnish on primary teeth. She divided 222 Alachua County Head Start children into two groups. One group received an application of fluoride varnish at the beginning and again four months later. The control group was given a gel commonly used in dental offices at the same intervals.

"We found that at the end of the study, the progression of dental caries had reversed (remineralized) in more than 80 percent of the test group and 37 percent in the control group," Dr. Autio reported. She routinely had used fluoride varnish as an anticaries agent in Finland before relocating to Florida in 1997.

Duraphat cannot be sold over-the-counter because of the very high fluoride concentration (22,600 ppm as compared to 1,000 to 1,400 ppm in toothpastes.) In the office, it takes less than two minutes to apply as the patient's saliva aids in the quick adherence of the varnish to the teeth. This form of application is excellent for patients with special needs or those who live in high-risk areas for dental decay.

Other studies are now being done to determine the effectiveness of fluoride varnishes to fight decay. Dr. Autio plans to conduct another study on Head Start children to determine varnish effectiveness over a two-year period.

The lozenge approach

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A new method of home application is the fluoride lozenge. Shirley Gutkowski, RDH, represents a company that makes sodium fluoride lozenges called Lozi-Flur. "Lozi-Flur lozenges have been FDA approved. The ADA approved Lozi-Flur as an anticaries agent in children," Gutkowski said. "Because of the low dose, 1 mg of fluoride ion from 2.21 mg neutral sodium fluoride, they are safe for children age six and over. (The FDA has established that 264 mg of sodium fluoride is safe for home storage, which is 64 mg more than a full bottle of the lozenges.) The lozenges bathe the teeth for eight to 12 minutes, with fluoride remaining in the saliva for 30 minutes after ingestion. The fluoride that is swallowed provides a systemic effect for children whose teeth are still forming."

Dreir Pharmaceuticals manufactures Lozi-Flur, and its president, Dr. Robert Reed, explained that the FDA did not require specific testing of the product because of the pre-existence of the 1 mg fluoride tablet from years ago. Still, it took 10 years of research to satisfy the FDA. Finally, in April 1998, Lozi-Flur became available.

"What we have done is to take that same 1 mg from the tablet and incorporate it into a lozenge, making it last over an extended period of time. We recommend fluoride lozenges for patients who don't have fluoride in their drinking water," Dr. Reed said. "Our prime patient target is adults, fluoride in the water notwithstanding. Four hundred commonly prescribed drugs treat illnesses such as cancer and heart disease while creating a dry mouth or xerostomia. Radiation treatments also can damage salivary glands, paving the way for rampant decay. Since saliva is our first line of defense against tooth decay, this is a big problem. Lozi-Flur inhibits the formation of new caries and remineralizes tooth enamel. It is designed to replace products such as gels, rinses, and high-concentration dentifrices. Some patients use this product simply to protect the investment they have made in their oral health."

Even though the FDA didn't require testing on Lozi-Flur, independent studies have been done on the product. Clinical Research Associates' (CRA) studies, for example, have rated Lozi-Flur very highly. Patients using Lozi-Flur and the doctors who prescribe it comment on reduction of decay and sensitivity, as well as an improvement of tissue health and compliance. More information about Lozi-Flur can be obtained at

Many factors have to be taken into account when choosing the right fluoride and delivery method for patients. They trust you to make the right decision for their oral health. As clinicians, we need to be skeptical and seek the evidence of independent studies to ensure we are doing our best for patients. If we can't find any convincing proof, we should rethink our rationale for using that product. After all, we are all somebody's dental patient. Wouldn't you expect your dental office to do the same for you?

Joanne Iannone Sheehan, RDH, is a frequent contributor to RDH. She is based in Huntsville, Ala.

In two parts

Another delivery system is the two-part fluoride rinse. In 1996, about 50 percent of dental offices were using the two-part rinse.

Two-part fluoride rinses - 0.31 percent APF and 1.64 percent stannous fluoride (SnF2) - are used one at a time or are mixed. It has been used as:

  • Two one-minute rinses of APF solution followed by two one-minute rinses of SnF2 solution.
  • A one-minute rinse of APF followed by a one-minute rinse of SnF2.
  • Two one-minute rinses with a combined solution of APF and SnF2.

Hygienists use this method when patients complain about the trays and swallowing fluoride. They may also think it's more convenient and less costly. But let's examine the validity of those complaints.

Patients typically complain about the heavier texture of fluorides and, because of poorly fitting trays, swallowing the excess. Foams can replace the gels and eliminate the oozing of excess gel, thus allowing little or no ingestion. Choosing the correct size tray is essential for a good fit and minimal leakage. The tray should be the right depth to make sure the fluoride reaches the cervical areas of the teeth where root caries or white-spot lesions are a problem. If the tray is a poor fit, the fluoride is not applied evenly and the procedure is not as effective as it could be.

There has been some concern about the potential of accidentally swallowing rinses. The level of fluoride in a rinse could cause acute fluoride toxicity in a child if swallowed. The age of the patient should be taken into account when choosing the method of application. When treating small children, a rinse may not be the answer.

Sometimes patients mistakenly believe that if they ask for the rinse instead of the trays, they won't have to wait for 30 minutes before eating or drinking. But Clinical Research Associates (CRA) cites studies indicating that "enamel treated with APF four minutes in vivo had about 50 percent lower fluoride retention if subjects rinsed after application."

Patients also may think of two-part rinses as being less expensive. They are ... for the doctor. Rinses cost less to purchase than foams or gels in many cases. Only the doctor can decide if the savings is passed along to the patient. But, because two-part rinses have not been sufficiently researched regarding anticaries effectiveness, the rinse may be highly costly to the patient during future restorative treatment. As a matter of fact, fluoride researchers warn clinicians that the chances are very unlikely that a rinse with 1,500-3,000 ppm could be as effective as topical fluoride with 9,000-12,300 ppm delivered in a tray.

So the question remains ... can a two-part fluoride rinse be used effectively in place of a conventional gel/tray treatment in the office? Again, CRA says the answer to that question is "uncertain."

The CRA Newsletter stated in 1990, "Although laboratory studies have been generally favorable, there have been no randomized double-blind clinical studies demonstrating efficacy of this concept for professional use. Efficacy with professional use is questioned for three reasons: fluoride is delivered in the presence of saliva; low fluoride concentrations are used; and contact times of less than four minutes are often used. Therefore, use should be limited to patients who refuse gel/tray fluoride application.

Lynn Tolle-Watts, RDH, a professor at Old Dominion University in Norfolk, Va., echoed these reservations about this product: "I am aware there is not research backing up the claims of the two-part fluoride rinses and do not advocate their use as a result. I believe their use in practice is related to their ease of use. I think many practitioners believe this makes up for the lack of science and or just depend on the claims of the sales rep."