Fluoride gel (i.e., 1.23% APF) is an acidic, highly concentrated fluoride treatment that dentists apply to patients teeth about two times a year. The gel contains 1.23% fluoride, which equates to 12.3 mg of fluoride for every 1 mL. Since dentists apply anywhere from 4 to 8 mL of gel for each treatment, a patient can be exposed to up to 100 mg of fluoride in a single sitting. (Whitford 1987). If this gel is swallowed, symptoms of acute toxicity can occur, including gastric pain, nausea, vomiting, dizziness, headache, and even death. (Ekstrand 1981). What makes fluoride gel particularly dangerous is that its high acidity (pH < 4) greatly increases the flow of flow, making it harder to resist swallowing, and turning the fluoride into hydrofluoric acid (a chemical that readily permeates the oral and gastric mucosa, thereby readily entering the bloodstream). Accordingly, studies have found that professional application of fluoride gels can lead to rapid and dramatic spikes in the blood fluoride level (up to 1,450 ppb in children and up to 950 ppb in adults). (Ekstrand 1987). While dentists have taken measures to reduce the amount of fluoride that gets into the bloodstream, (Hawkins 2003; LeCompte 1987) it is estimated that children will still swallow an average of 7.7 mg per treatment, (Hawkins 2003), while adults will swallow an average of 10.3 mg. (Johnston 1994).

overview:

“The purpose of professional fluoride treatments is to benefit the tooth enamel by a topical effect, not by systemic ingestion. Therefore, in an ‘ideal’ topical application procedure, the patient would swallow no fluoride.”
SOURCE: Lecompte EJ. (1987). Clinical application of topical fluoride products–risks, benefits, and recommendations. J Dent Res. 66(5):1066-71.

“The use of 1.23% (12,300 ppm) APF gels, particularly in the absence of suctioning during the application and expectoration after the application, is associated with the swallowing of relatively large quantities of fluoride. The resulting increases in plasma fluoride levels may be sufficient to cause dental fluorosis, as judged by studies with laboratory animals, and a reduction in the kidney’s ability to concentrate the urine, as judged by studies with both laboratory animals and humans. The epigastric distress experienced by some patients during or after APF gel applications appears to be due, at least in part, to a direct toxic effect of fluoride on the gastric mucosa. Data from studies with humans and laboratory animals indicate that there may also be associated changes in plasma and tissue cAMP levels, glucose metabolism, and salivary amylase secretion. There is an immediate need for the dissemination to the dental profession of standardized methods for gel application that will minimize the quantities of fluoride available for ingestion and systemic absorption.”
SOURCE: Whitford GM, et al. (1987). Topical fluorides: effects on physiologic and biochemical processes. J Dent Res. 66(5):1072-8.

“It is concluded that following the use of topical fluoride products, variable amounts of fluoride are swallowed and absorbed into the systemic circulation–amounts which may be sufficient to produce acute or chronic side-effects.”
SOURCE: Ekstrand J. (1987). Pharmacokinetic aspects of topical fluorides. J Dent Res. 66(5):1061-5.

Fluoride Gels Increase Saliva Flow

“Studies have shown that salivation and swallowing are stimulated by application of topical fluorides, paticularly in the acidulated form, and a considerable amount of fluoride may be ingested during professional application of topical fluoride, particularly by young children.”
SOURCE: Johnston DW. (1994). Current status of professionally applied topical fluorides. Community Dent Oral Epidemiol. 22(3):159-63.

“Since most of these gels are both acidulated (pH 3.5) and flavored, they stimulate salivation. This enhances swallowing of excess saliva and gel during application.”
SOURCE: Ekstrand J, Koch G. (1980). Systemic fluoride absorption following fluoride gel application. J Dent Res. 59(6):1067.

The Dose of fluoride:

“The 1.23% APF gels contain the [fluoride] ion at a concentration of 12,300 ppm. Each gram of gel contains 12.3 mg of fluoride. The pH of the gels is distinctly acidic (pH < 4), so that about one-half of the fluoride exists in the form of hydrofluoric acid (HF). This may promote the rapid absorption of swallowed fluoride, resulting in early and unusually high peak plasma concentrations. Moreover, relatively large quantities of the gels (from 4 to 8 mL) are used with each treatment, so that from 49 to nearly 100 mg of fluoride are usually applied.”
SOURCE: Whitford GM, et al. (1987). Topical fluorides: effects on physiologic and biochemical processes. J Dent Res. 66(5):1072-8.

“The “probably toxic dose” (PTD) is approximately 5 mg F/kg, which is only 4.1 ml of 1.23% APF gel for a child weighing 10 kg.”
SOURCE: Tsai CL, et al. (2008). Induction of apoptosis in rabbit oral mucosa by 1.23% acidulated phosphate fluoride gel. Arch Toxicol. 82(2):81-7.

Recommendations:

“(1) No more than 2 g of gel per tray or approximately 40% of tray capacity should be dispensed. Even more conservative amounts should be considered for small children. (2) Because patients may have the need to swallow during a four-minute topical application procedure, the use of a saliva ejector during the procedure is recommended. (3) Following the four-minute application procedure, the patient should be instructed to expectorate thoroughly for from 30 sec to one min, regardless of whether high-speed suction is utilized. Expectoration is probably the single most effective way of reducing orally retained fluoride. (4) When utilizing custom individually fitted trays for patients requiring daily or weekly application of a high-F-concentration product, utilize only 5 to 10 drops of product per tray.”
SOURCE: Lecompte EJ. (1987). Clinical application of topical fluoride products–risks, benefits, and recommendations. J Dent Res. 66(5):1066-71.

Even if Recommended Measures are followed, Fluoride Absorption Is Inevitable

“A considerable amount of fluoride may be retained after gel application, even if suction devices are used (on average 7.7 mg in children).”
SOURCE: Hawkins R, et al. (2003). Prevention. Part 7: professionally applied topical fluorides for caries prevention. Br Dent J. 195(6):313-7.

“Even under optimum methods of application children may swallow an average of about 11 mg of fluoride ion. . . . Virtually all retained oral fluoride is swallowed and subsequently absorbed in fasting individuals and the bio-availability has been reported to be 100%.”
SOURCE: Johnston DW. (1994). Current status of professionally applied topical fluorides. Community Dent Oral Epidemiol. 22(3):159-63.

“It is questionable whether these highly concentrated fluoride gels should be used in pre-school children at all because of the risk of toxic side-effects. The prevention of inadvertent swallowing of some of the applied gel is difficult, perhaps almost impossible, in small children.”
SOURCE: Ekstrand J. (1987). Pharmacokinetic aspects of topical fluorides. J Dent Res. 66(5):1061-5.

“Absorption from the gastrointestinal tract subsequent to inadvertent swallowing appears to be the major route for this systemic exposure. There are, however, two reports which have shown that fluoride is absorbed via the oral mucosa of the rat so that, even in the total absence of swallowing, some systemic absorption would be expected.”
SOURCE: Whitford GM, et al. (1982). Fluoride absorption through the hamster cheek pouch: a pH-dependent event. J Appl Toxicol. 1982 Dec;2(6):303-6.

Print PDF