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Fluoride Definition

Fluoride is a negatively charged fluorine atom (F), also known as a fluorine anion. Fluoride is a naturally occurring ion, found in certain mineral and salty deposits. Certain levels of fluoride have been proven to be beneficial in fighting cavities and strengthening teeth. As a public health measure, fluoride has been maintained at low levels in municipal drinking water in many countries, including Australia, the United States, and several European countries. While there remains some controversy over the dangers of fluoride in water, the level is maintained well below the documented level at which negative symptoms are seen.

Biochemistry of Fluoride

Fluoride, as a negative ion, or anion, is capable of binding ionically to a cation, or positive ion. In the blood, there are many cations, but of utmost importance are H+ (hydrogen) and Ca2+ (calcium). These cations must be maintained in strict balance. If they are not in balance, the system will become more acid, and more calcium will be drawn from the bones and teeth, making them weaker and brittle. If a person has two little fluoride or too much fluoride in their system, these cations will also become unbalanced.

On the short hand, too little fluoride creates weak teeth, and allows bacteria to infiltrate and infect. This leads to tooth decay and cavities. Very low levels of fluoride prevent calcium from leaving the teeth, thereby strengthening them and preventing bacterial invasions. It is for this reason that water supplies are fluorinated on purpose. Fluoride provides an efficient, cost-effective method of providing a basic preventative health service.

On the other hand, too much fluoride in the system can be a bad thing. Just as too little fluoride weakens the bones, too much fluoride causes the same condition. Instead of limiting the system which balances calcium in the bones and teeth, fluoride can become the negative anion which pushes it out of balance. With too much fluoride in the system, the pH begins to lower. This causes the release of calcium, which can soak up acids in the blood. The calcium is then lost in the urine, and the bones and teeth become weaker.

Your body has this natural ability to process and remove excess fluoride, and can expel up to 50% of the fluoride intake per day. However, this means that long exposures to medium doses or single exposures to very high doses will take time to be removed from the system. At a certain point, they can become deadly, but this point is far above the threshold we keep our fluoride levels at.

Uses for Fluoride

Fluoride in Drinking Water

Health professionals have been maintaining low levels of fluoride in drinking water for many decades, as there is much evidence that it decreases tooth decay by killing bacteria in the mouth. The low levels of fluoride added to drinking water are far below the maximum limits of 7-10 mg per day that a human can safely consume. While many millions of people drink fluorinated water, controversy remains around its effects and potential side-effects. Much of this is due to the harsh effects of fluoride at high levels, seen in some natural ground water sources. Municipal sources of water are specially treated and screened to prevent high levels of fluoride. See “Dangers of Fluoride” below, for more information.

Fluoride in Dental Products

Fluoride is a common component in many dental products, including toothpastes, varnishes, and other teeth cleaning products. Fluoride has a proven history in the fight against mouth disease. It is also incredibly cheap, and reliable to work with. However, in the early days of using fluoride in dentistry there were some unfortunate accidents. Several people got sick, and even died, when they misused concentrated fluoride solutions provided by their dentists. While the solutions were intended to be spit out, the patients swallowed the concentrated fluoride. The high dose of fluoride disrupted their pH and calcium content enough to cause death.

These situation have been easily avoided by the setting of guidelines to the use of fluoride and strict warning labels on products which contain fluoride. Fluoride toothpastes usually contain a fraction of the daily advised amount of fluoride, and most of the fluoride is not absorbed when properly used. Concerns over children and fluoride poisoning have led to children’s toothpastes, which have a reduced fluoride content.

Other Places Fluoride is found

Fluoride is found naturally nearly everywhere. There is fluoride present in seawater, at nearly the same levels government fluorine their water. There is also some present in rainwater, which has fallen from the atmosphere after being deposited there by fires, volcanoes, and industrial pollution. The majority of fluoride on the Earth is found as the salt crystal fluorite (CaF2). This crystal can be mined, and the fluoride can be extracted for industrial applications. Because fluoride is found in rain and water, it is also found in plants. Therefore, everything we eat has trace amounts of fluorine.

Dangers of Fluoride

While there are virtually no well documented dangers to the levels of fluoride we are exposed to in the water, there is a danger of having no or too much fluoride. Fluoride is a necessary part of several biological reactions, and most living organisms need at least trace amounts of it to function properly. Where this threshold is exactly is not known, but even as little as half a milligram per liter of water can drastically improve bone and tooth health.

On the flip side, too much fluoride can have drastic consequences. Beginning symptoms of excess fluoride include dental and skeletal fluorosis. This is a condition in which the calcium starts to leave the bones to deal with the excessively high blood pH. As the calcium leaves, it is replaced by fluorine. This can make the bones and teeth excessively hard and brittle, causing them to break or shatter more easily. These symptoms can be slowly reversed by cutting fluoride out of the diet. These diseases have been documented in cases where the fluoride in the drinking water was above 10 mg/L, which is almost 10 times the amount in North American drinking water.

Exposure to higher levels of fluoride can cause more severe symptoms. At the far end of the spectrum is hypocalcemia. Your body, in order to counterbalance the huge amount of negation ions you just ingested, rapidly pulls the calcium from all of your tissues, not just the bones and teeth. As this happens, critical junctions at nerve and muscle cells can no longer function. Your body shuts down quickly, and you die. This condition is known as hypocalcemia. Fluoride has caused several deaths this way, mostly in accidents involving concentrated fluoride chemicals for industrial purposes. While fluoride is not a problem for nations with sophisticated water treatment facilities, high levels of fluoride are consumed by over 300 million people a year from untreated groundwater sources.

In drinking water in the United States, the fluoride is maintained between 0.7 and 1.2 mg per liter. A human can drink around 3-4 liters of water per day, which brings their total fluoride intake to somewhere between 4-5 mg. A daily intake of less than 10 mg is recommended, allowing much room before significant levels of fluoride are reached. In groundwater sources which contain more fluoride than this, the fluoride can quickly accumulate and cause a wide variety of issues.


1. Is fluoride harmful or beneficial to your health?
A. Harmful
B. Beneficial
C. It depends how much you take

Answer to Question #1
C is correct. All things can become poisonous if you take too much of them. Fluoride is no different. Your body needs some fluorine atoms to complete various chemical processes. However, your body is not used to dealing with too much fluoride, and because it is an ion, it can severely disturb bodily functions.

2. Which of the following is a serious concern about fluoride?
A. The Communists are using it to control our brains
B. Too much fluoride will cause mutations and deformations
C. Too little fluoride will leave us with brittle bones and teeth

Answer to Question #2
C is correct. Of these choices, the most concerning is our oral health. Trace amounts of fluoride are apparently a necessary part of healthy teeth. While excess fluoride can be an issue, it doesn’t cause mutations and really isn’t a concern if you are drinking treated water.

3. Fluorite (CaF2) is the salt crystal which is mined to extract fluoride. Approximately how much fluoride is obtained from two grams of fluorite? Hint: you might want to look at the periodic table.
A. 0.25 grams
B. 1 gram
C. 1.5 grams

Answer to Question #3
B is correct. When you look at the periodic table, you will notice that fluorine is atomic number 9, and calcium is number 20. That means that fluorine weighs approximately half of calcium. Fluoride is simply fluorine with a negative charge. Therefore, in 2 grams of fluorite (the crystal) there is approximately 1 gram of calcium (20) and 1 gram of fluoride (9 + 9 = 18). It wouldn’t be exactly 1, but that’s close enough for the answers to this question.


  • Bruice, P. Y. (2011). Organic Chemistry (6th ed.). Boston: Prentice Hall.
  • Nelson, D. L., & Cox, M. M. (2008). Principles of Biochemistry. New York: W.H. Freeman and Company.

Cite This Article

Biologydictionary.net Editors. "Fluoride." Biology Dictionary, Biologydictionary.net, 01 Apr. 2018, https://biologydictionary.net/fluoride/.
Biologydictionary.net Editors. (2018, April 01). Fluoride. Retrieved from https://biologydictionary.net/fluoride/
Biologydictionary.net Editors. "Fluoride." Biology Dictionary. Biologydictionary.net, April 01, 2018. https://biologydictionary.net/fluoride/.

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