If during the application phase of the elements (before the breakthrough, also called pre-eruptive phase) there is a too high fluoride concentration in the blood for a longer period of time, there is a high risk of disturbance of the enamel formation. Clinically this is visible after breakthrough in the form of white spots in the enamel ("mottled enamel").
If a too large dose of fluoride is administered after the breakthrough (post-eruptive phase), this will not cause dental abnormalities.
For general health, however, it is important to know that taking too much fluoride can quickly lead to poisoning (intoxication) and is therefore certainly not without danger. In a gel application, something is often swallowed and that is why the original gel with 1.23% fluoride has been replaced by the now generally used gel with 0.4% fluoride.
When receiving about 3.75 mg of fluoride per kilogram of body weight, there is an overdose. Because fluoride affects the mucous membrane of the stomach wall, nausea and abdominal pain often occur. It is recommended that the patient drink a lot, preferably milk: milk binds fluoride so that it is no longer absorbed. This measure must be taken very quickly because fluoride is absorbed very quickly (within half an hour!) From the stomach into the bloodstream.
Ingestion of more than 3.75 mg of fluoride per kilogram of body weight gives rise to poisoning symptoms: 3.75-5 mg of fluoride per kilogram is a mild poisoning with potentially serious consequences. , and more than 15 mg of fluoride per kilogram of body weight will certainly result in death. This is also called the lethal dose.
In an application spoon, therefore, only a maximum of 10 ml of fluoride gel should be applied to remain below the toxic dose. The top and bottom together may therefore not exceed 20 ml of gel of 0.4% (20 x (0.4% x 1 ml) = 20 x 4 mg = 80 mg) (1 ml = 1 gram = 1000 mg). If the applications are started at the age of five, an average child will then weigh around 20 kg. If that child unfortunately swallows all fluoride gel from the spoon instead of spitting it out, 4 mg of fluoride per kilogram of body weight has arrived. That is then a case of maximum overdose, but not yet of poisoning.
Fluoride tablets are notorious for being relatively easy to cause poisoning in small children. After all, they look like sweets and also taste good, at least: not dirty. Not only nausea, but also sleepiness can occur. Due to the excessive amount of fluoride, breathing can become slower. An oxygen deficiency occurs in the brain and the patient yawns to breathe deeper.
Very severe poisoning can cause the patient to die (lethal dose).
As a practical rule applies: eating 100 fluoride tablets or 1 tube of children's toothpaste in a short period of time must be followed immediately by vomiting and then drinking a lot of milk. In addition, when receiving 300 fluoride tablets or 1 tube of adult toothpaste, the victim must be taken quickly to the hospital for gastric lavage and for monitoring the amount of calcium in the blood to prevent a life-threatening disruption of vital organs.
So if poisoning is feared, fast action is necessary. If there is uncertainty about the amount of fluoride absorbed, it is good to contact the doctor and, if necessary, have the stomach drained. All of this must be done within 30 minutes, as noted earlier, because fluoride is absorbed very quickly from the stomach!