Fluoride Action Network

Side Effects from Fluoride Gels: Gastric Distress

Fluoride Action Network | April 2012 | By Michael Connett

Gastric distress — including nausea, pain, and vomiting — is one the most common side effects from professional application of “fluoride gels” at the dentist. Patients receiving fluoride gels can swallow more than 20 mg of fluoride from a single treatment — doses that far exceed the doses that can form toxic concentrations of hydrofluoric acid in the stomach. While the dentists now use measures to reduce the amount of fluoride that is swallowed, it is estimated that children still swallow an average of 7.7 mg per treatment, while adults swallow an average of 10.3 mg. (Johnston 1994). Such doses still exceed the doses that cause damage to the gastric mucosa. Indeed, as the data in the table below shows, a single dose of just 3 mg (the lowest dose tested) can cause widespread erosion of the gastric lining. (Spak 1990).

Gastric Symptoms following application of Fluoride Gel:

“[T]he most likely symptoms to manifest in patients from professionally applied topical fluorides are nausea and possibly vomiting. The irritation caused by topical fluoride gel to the gastric mucosa has been described. The observation by clinicians and researchers that nausea and vomiting are occasional manifestations of inadvertent ingestion of high fluoride ion from topical fluorides, particularly by young children, identifies the need to minimize unintentional swallowing of excess fluoride from dental products.”
SOURCE: Johnston DW. (1994). Current status of professionally applied topical fluorides. Community Dent Oral Epidemiol. 22(3):159-63.

“Several investigations have shown tissue disruption and cellular injury of rat gastric mucosa following the administration of amounts and concentrations of F much lower than [the concentrations produced by topical fluoride products]. This may help explain why children and adults sometimes complain of nausea and occasionally exhibit vomiting following topical F treatments.”
SOURCE: Lecompte EJ. (1987). Clinical application of topical fluoride products–risks, benefits, and recommendations. J Dent Res. 66(5):1066-71.

“Complaints of nausea, vomiting, or epigastric pain by patients receiving topical APF gel applications or those who have ingested other high-concentration fluoride preparations are not uncommon. . . . [F]unctional and structural findings from laboratory animal studies support the argument that patient complaints of epigastric distress after swallowing fluoride in high concentrations are due to a direct local toxic effect of the ion on the gastric mucosa. They also indicate the need to adopt standard application techniques that will reduce the quantities of fluoride available for swallowing.”
SOURCE: Whitford GM, et al. (1987). Topical fluorides: effects on physiologic and biochemical processes. J Dent Res. 66(5):1072-8.

“The amount and concentration of F ingested may help to explain why children often complain of nausea and occasionally exhibit vomiting following topical F application. Easmann et al have shown disruption of rat gastric mucosa following the administration of amounts and concentrations of F lower than those used in this study.”
SOURCE: LeCompte EJ, Whitford GM. (1982). Pharmacokinetics of fluoride from APF gel and fluoride tablets in children. J Dent Res. 61(3):469-72.

“One the subjects experienced nausea and slight dizziness.”
SOURCE: Ekstrand J, Koch G. (1980). Systemic fluoride absorption following fluoride gel application. J Dent Res. 59(6):1067.

TABLE: Dose of Fluoride vs. Gastric Mucosa Damage

Values for Macroscopic and Microscopic Evaluation of the Gastric Mucosa in Control Conditions (C) and After Fluoride Application (F)
Subject Macroscopic Evaluation* Microscopic Evaluation ** Retained Amount
of Fluoride
Corpus Antrum Corpus Antrum
LB 0 1 0 1 0 1 0 1 6.0
KT 2 4 0 3 0 1 0 0 3.4
EF 0 4 0 3 0 1 0 0 7.8
IT 0 4 0 2 0 1 0 1 9.2
AL 0 1 0 0 0 1 0 1 3.1
MJ 0 0 0 0 0 1 0 1 3.2
MW 0 4 0 1 1 2 0 0 3.9
HD 0 0 0 0 0 1 0 0 5.3
LJ 0 0 0 0 1 0 1 1 4.1
PK 0 3 0 2 0 1 0 1 5.3
Mean 5.1
SD 2.1
* Macroscopic Evaluation:0 = normal
1 = 1 petechia or erosion
2 = 2 – 5 petechiae or erosions
3 = 6 – 10 petechiae or erosions
4 = >10 petechiae or erosions, widespread involvement of the stomach with petechiae or erosions, ulcer of any size.

** Microscopic Evaluation

0 = normal
1 = either surface epithelium alteration with stroma edema/ hemorrhage or gastric pit damage
2 = both surface epithelium and gastric pit damage
3 = as number 2 combined with acute inflammatory cellular response

SOURCE: Spak CJ, et al. (1990). Studies of human gastric mucosa after application of 0.42% fluoride gel.Journal of Dental Research 69:426-9.