In-office procedures administered to children may result in excessive fluoride ingestion and is an area of concern
Mary Danusis Cooper, RDH, MS and
Connie Myers Kracher, CDA, BSEd
Although dental professionals and consumers have always thought that more fluoride protection is best for reducing dental caries, some concerns have arisen in recent years. Evidence proves that there has been an increase in dental fluorosis as a result of the increased exposure to fluoride during tooth development. The rise in fluorosis is prevalent in both non-fluoridated and fluoridated communities.
The increase, fortunately, has been limited to milder exposures. The availability and use of fluoride-containing products for home use - such as toothpastes, rinses, and supplements - has contributed to this rise as well. In part, an increase in the daily intake of fluoride from the diet - largely from carbonated drinks - may be a likely cause of dental fluorosis.
An area of concern includes professional fluoride applications. Added care needs to be taken in monitoring fluoride treatments in the dental office. This monitoring would hopefully decrease the amount of fluoride applied, thus preventing accidental swallowing by the patient during application. Children younger than 6-years-old, in particular, need to be watched carefully, since this age group has the greatest incidence of accidental ingestion of fluoride.
No one questions the efficacy of fluoride in reducing tooth decay. Studies prove conclusively that the incorporation of fluoride in drinking water can reduce decay by as much as 40 percent in some areas of the United States. In addition, the role of fluoride in the decay process is two-fold. It can also arrest and reverse incipient lesions.
This delivery system benefits over 50 percent of the population. It is also inexpensive, costing each person approximately 50 cents annually.
Signs and symptoms of acute fluoride toxicity
Before discussing treatment measures, an understanding of the body`s dynamics of metabolizing fluoride is important, as well as possible risk factors involved with excess fluoride ingestion. Fluoride is absorbed into the blood from the gastrointestinal tract. Most fluoride is then deposited in the bone or excreted by the kidney.
When above normal amounts of fluoride are ingested, the fluoride combines with hydrochloric acid in the stomach and forms hydrofluoric acid. As a result, the hydrofluoric acid has a burning effect on the gastric lining causing gastrointestinal (GI) symptoms such as nausea, vomiting, abdominal cramping, and discomfort.
Even higher dosages of fluoride ingestion may result in hypercalcemia. Calcium is essential for the integrity of the nervous system. However, fluoride will bind to the calcium when excessive amounts of fluoride have been ingested, resulting in a drop of blood calcium. Therefore, symptoms such as muscle tetany and parasthesia will likely develop.
Acute fluoride toxicity has been associated with hyperkalemia as well, resulting with the onset of the "three C`s" - coma, convulsions, and cardiac arrhythmias. The 24 hours following ingestion are critical to the patient`s chance of survival, and proper emergency treatment is vital.
Treatment of fluoride toxicity should be administered immediately. Upon excess fluoride ingestion, milk should be given to the patient to help protect the lining of the stomach. The milk also provides the necessary calcium to which the fluoride can bind.
Many professionals question the practicality of having milk on hand in the office. Other products can be substituted to essentially provide the same results, such as lime water, Maalox, or a can of condensed milk. The alternative products, of course, can be kept indefinitely.
How much fluoride is too much? The exact toxic and lethal dose of fluoride are difficult to determine. Although both age and weight standards have been used, weight by kilogram is used most readily today. A child who has ingested up to 5 mg/kg (2.2 pounds equals one kilogram) of fluoride may only experience mild gastrointestinal discomfort. Induced vomiting is not necessary, but calcium (milk) should be taken orally to help relieve the GI symptoms. Following this, observation of the patient will be necessary for a few hours.
Fluoride ingestion of greater than 5 mg/kg but less than 15 mg/kg can produce much more serious symptoms. If the patient does not spontaneously vomit, digital stimulus - of the back of the throat - or syrup of ipecac can be used. Vomiting does help expel the majority of the fluoride which has been ingested. Again, the patient should be given calcium orally.
Additionally, however, the patient should be admitted to the hospital for proper monitoring of the heart as well as the monitoring of calcium, magnesium, potassium, and pH levels. Intravenous calcium may be required to restore blood calcium and magnesium levels to normal ranges.
Ingestion of fluoride greater than 15 mg/kg requires that the patient be admitted to the hospital immediately. The stomach needs to be emptied and a solution of calcium gluconate solution must be administered intravenously. Cardiac monitoring is necessary to observe the possible onset of cardiac arrythmias. The patient also needs to be observed for the potential onset of muscle tetany, parasthesia, coma, and convulsions.
High levels in professional products
The purpose of professional fluoride treatments is to benefit the tooth enamel by topical effect, not by systemic ingestion. An ideal procedure for a topical fluoride application administers fluoride without the patient swallowing any. Unfortunately, many variables affect fluoride retention and ingestion by the patient - the type and size of application tray, type of fluoride product, the amount of fluoride used, patient expectoration, and aspirating devices used during the application.
Professionally applied fluoride products include high levels of fluoride concentration that range between 9,000 to 19,000 parts per million (ppm), which is equivalent to 9 to 19 mg of fluoride per millileter of product. The three fluoride products used in dentistry, which are approved by the FDA and ADA for professional application, are:
- 1.23 percent acidulated phosphate fluoride (APF).
- 2 percent sodium fluoride (NaF).
- 8 percent stannous fluoride (SnF2).
Acidulated phosphate fluoride continues to be the most popular fluoride used among dental professionals. It contains 12,300 ppm or 12.3 mg of fluoride per ml with a phosphoric acid pH of approximately 3.5. The ppm of sodium fluoride and stannous fluoride range between 9,000 to 19,000, respectively.
Studies indicate that the amount of fluoride removed from the oral cavity, as well as the amount of fluoride retained in the mouth of a child patient during a four-minute fluoride application, raises a cause of concern.
The amount of fluoride applied by dental professionals is not standardized. The average amount of APF gel dispensed per tray ranges between 2 to 3.6 grams. Most trays (both arches) hold a maximum of 5 grams of gel. Care should be taken in dispensing the correct amount of fluoride into the trays.
As stated earlier, the greatest incidence of accidental ingestion of fluoride products occurs most frequently in children younger than 6 years old. One study indicated that, with an application of 49.2 mg of fluoride, an average of 32.3 mg of fluoride was removed with the tray, leaving a remaining 16.9 mg of fluoride in the mouth.
If complete removal of the residual fluoride is not accomplished, the amount remaining, if swallowed, could be toxic.
Risks with home-use fluoride products
Several over-the-counter products contain fluoride, including most dentifrices and mouthrinses. In the United States, 99 percent of the toothpastes marketed contain fluoride in concentrations between 1,000 to 1,500 ppm. These formulations contain approximately 0.1 percent fluoride from either sodium fluoride or monofluorophosphate. Normal brushing with a ribbon of toothpaste provides about 1 gram of toothpaste and will expose an individual to approximately 1 mg of ingested fluoride per brushing.
Most economy/family size toothpastes (8.2 ounces, 1,000 ppm) contain 240 mg of fluoride. This amount is the upper limit for the amount allowed in dentifrices and is also 2.5 times the probable toxic dose (PTD) for children five years of age. The same size container of toothpaste with 1,500 ppm of fluoride has more than 3.5 times the PTD for a 5-year-old.
Concern arises with this age group because most children under the age of six have a tendency to swallow the toothpaste during brushing. An estimated 25 percent (although the range can be from zero to 100 percent) of the fluoride in toothpastes is swallowed when children are left unsupervised during brushing.
The amount ingested is greater than that recommended for systemic supplementation. So there is justifiable concern that fluoride in dentifrices can contribute to dental fluorosis in children of preschool age, especially if they are already receiving optimal amounts of fluoride in their drinking water. Even Procter & Gamble`s Crest "Sparkle" toothpaste for kids - a popular children`s toothpaste in the United States because of its bubblegum flavor and colorful appearance - contains 1 gram of fluoride per ribbon of toothpaste. The possibility of ingestion would be 1.2 mg of fluoride with each brushing.
Recommendations for home use products
For reasons stated earlier, it is highly recommended that children, especially under six years of age:
- have parental supervision with dentrifice use as well as with home fluoride rinses.
- Use only a pea-sized amount of toothpaste.
- Be cautioned not to swallow or eat the toothpaste and taught to expectorate and rinse as early as possible.
It would also be beneficial for manufacturers of dentifrices to add a warning on the label, stating the appropriate amount to use for children under six years of age.
In addition, over-the-counter mouthrinse products should be limited to 120 mg of fluoride or 522 ml of mouthrinse. All at-home fluoride mouthrinse products for daily use contain NaF, APF, or SnF2 with fluoride concentrations of approximately 0.02 percent. These products are diluted as a simple measure to expose teeth to fluoride frequently - yet at a safer amount to help prevent fluoride toxicity.
The recommended 10 ml volume for all of these rinses contains less than 2.5 mg of fluoride, a safe amount even if accidentally swallowed. These products should have a child-proof cap and a measuring device for safe and effective dispensing.
Mouthrinses are contraindicated for preschool age children because of their lack of control with swallowing reflexes. A warning does appear on the label of these products to caution adults regarding the proper use. However, as with the recommendation for any medication, it is best to store all fluoride-containing products out of the reach of children.
Recommendations for professional use products
The following guidelines for professional application of APF gels are recommended:
- No more than 2 grams of gel per tray, or approximately 40 percent of tray capacity should be dispensed. More conservative amounts should be considered for young children.
- The use of a saliva ejector during the entire fluoride application time is recommended.
- The patient should be seated in an upright position.
- The patient should tilt the head forward during fluoride application so the excess amount of fluoride flows toward the anterior portion of the mouth which can be removed by the inserted saliva ejector.
- The patient should be instructed to expectorate thoroughly from 30 seconds to one minute after the fluoride application. Expectoration is the single most effective way of removing retained fluoride orally.
- Use well-fitted trays.
- When using custom-fitted trays for patients requiring daily or weekly applications, use only five to 10 drops of product per tray.
- The patient should never be left unsupervised during the fluoride application.
The incorporation of fluoride in dental products is essential in the prevention of caries. However, the increased exposure of fluoride from other sources, including ingestion of topical fluorides, can effect the incidence of dental fluorosis. Care needs to be taken when using fluoride-containing products (both professional and home use) to decrease the ingestion of fluoride, thereby minimizing the occurrence of fluorosis in children.
Parents/guardians and dental professionals need to be educated regarding the proper amount of fluoride that should be used to ensure the benefits from fluoride and yet reduce the risk of dental fluorosis.
Mary Danusis Cooper, RDH, MS, is an associate professor of dental hygiene at Indiana University/Purdue University-Fort Wayne in Fort Wayne, Ind. Connie Myers Kracher, CDA, BSEd, is an assistant professor of dental education at the same institution.