Question: Fluoride is found in places other than the town water. Why, and what does it do?

Fluoride causes the structure of the teeth to resist the break down of several of its components by the acid in dental plaque. Fluoride actually doesn’t make the teeth stronger, but makes them more resistant to dissolution by acid. Fluoride can be administered systemically or topically. Systemic delivery consists of swallowing fluoride and letting the body concentrate it in teeth and some other parts of the body. Systemic delivery of fluoride to the teeth is only effective during the formation period of the teeth. Topical delivery of fluoride consists of putting fluoride in direct contact with already formed teeth. To be effective against tooth decay, systemic fluoride is needed at a very low dose (one part per million or even less), but topical fluoride must be provided to the surface of the teeth at 1000 parts per million or higher.

Fluoride is found in nearly all commercially available toothpastes. The dose is one part fluoride per one thousand parts toothpaste. (One thousand times the dose found in fluoridated water.) This level is required to provide a thin layer of fluoride rich tooth structure on the outer surface of the tooth. It only penetrates about the thickness of a human hair into the tooth, and the effect is not permanent. It must be replenished often or the fluoride in the outer layer of tooth will leach into the saliva and be lost. The fluoride delivered in a twice a day brushing of the teeth with a fluoride toothpaste will reduce the chance of tooth decay on smooth surfaces of the teeth by about 30% beyond using a non-fluoridated toothpaste. If the person grew up in a community with fluoridated water, this effect is in addition to the effect of using low dose fluoride on the forming teeth (like the permanent effect gained from fluoridated water).

Fluoride is also available in a 5000 parts per million preparation at the dentist's office. This is usually delivered in a special foam tray to minimize swallowing. If left in contact with the teeth for one minute, another nearly 30% reduction of tooth decay on smooth surfaces of the teeth will be realized. This effect is also not permanent but lasts several months. Increasing the time the fluoride in the trays is in contact with the teeth to four minutes will increase reduction of tooth decay quite a bit but is not tolerated well by most people due to discomfort issues because of the longer delivery time required. A similar (but pH balanced) 5000 parts per million preparation is available without a prescription for use at home in place of regular toothpaste.

Administration of fluoride has been one of the most notable public health successes of the enlightened age. Fluoride has allowed millions of people to avoid billions of fillings and lost teeth. There is a caution. Although no serious public health problems have currently been proven, overdose should be prevented so that unsightly opaque white or brown spots are not caused in developing teeth. It is important to note that already erupted teeth cannot develop discolorations due to fluoride regardless of the dose. Discoloration of teeth because of too much fluoride is a condition strictly confined to the period of development of the teeth only. The most common source of too much fluoride is children eating toothpaste. A pea sized ball of toothpaste provides the same amount of fluoride that the average child receives from water in a community with fluoridated water in an entire day. As you can easily see, if the child swallows all this toothpaste in two tooth brushings every day and lives in a fluoridated community, the child will get three times the optimum level of fluoride every day. Care must be taken to keep children from using large amounts of toothpaste and swallowing after brushing.

Fluoride isn’t just for kids. As I have stated earlier in this series, the decade of life when a person is most likely to develop tooth decay is actually not the teenage years as in former times--it is the 70-80 year old period. Topical fluoride (fluoride placed directly on the teeth as compared to systemic fluoride which is ingested) is very effective for prevention of root cavities. Roots are much more susceptible to tooth decay than other parts of the teeth which have an enamel coating. More often than not, the fluoride provided in regular toothpaste (1000 parts per million) is not sufficient to prevent tooth decay on roots of people in the 70-80 year old period. One of the 5000 parts per million products used at least once per day provides much benefit to people with visible roots. Ask your dentist if you would benefit from using more topical fluoride.


This article was written by Dr. Mike Christensen and published in the Daily Miner and News, and Enterprise. Local Kenora News Publicatons (1998-2006)