Adding fluoride to water systems is done in order to reduce the number if children and adults who experience tooth decay. But there is a debate about the safety of such measures for instance there are claims that it increases them risk of cancer.
Since the early 20th century, the town of Hereford, in Deaf Smith County, Texas, was known as "the town without a toothache". Public health officials searched for a reason why this town had rates of dental decay that were significantly lower than average. It took nearly 12 years (from 1933 to 1945) for researchers to conclude through epidemiologic studies that it was the high naturally occurring levels of fluoride in its water that was responsible for this salutary effect on the residents of this town. On January 25, 1945, Grand Rapids, Michigan became the first city to intentionally introduce fluoride to its public water supply. Since that time, fluoridation of drinking water has become acknowledged by the Centers for Disease Control as one of the ten greatest public health accomplishments (see CDC / MMWR Report: Ten Great Public Health Achievements – United States, 1900-1999 at http://fluoride.oralhealth.org/papers/00056796.htm) Almost from the time of its introduction, however, the use of fluoride, especially in public water supplies, has been a topic of controversy.
Despite some dissension on this issue by non-dentists (and a minority of dentists), most researchers believe the literature supports the purported benefits of the use of fluoride as a public health measure. (Not a scientific fact but an empirical observation: during the years that I maintained a practice in Lindenhurst, a small village in Long Island with demographics similar to those of my current practice in Brooklyn, I noticed an incidence of dental decay MANY orders of magnitude greater than that encountered in Brooklyn. The only factor which I could see to account for this difference was that Brooklyn was fluoridated and Lindenhurst was not.) I remain convinced of the value of fluoridation.
Fluoride can be applied to teeth in one of two ways:
by application to the surface of the teeth (topically) through the use of fluoride-containing toothpastes, rinses, or professionally applied fluoride treatments, or
systemically, through fluoridation of drinking water or fluoride dietary supplementation.
The systemic application of fluoride is thought to benefit children whose teeth are still in the process of formation, because the fluoride introduced into the body can still be incorporated into the structure of the teeth. Since tooth enamel formation is generally completed by age 14 or 15, systemic fluoride is not thought to confer any benefit for those above this age.
In either method of application, fluoride becomes a part of the enamel structure. The main inorganic structural element of enamel, hydroxyapatite, becomes fluorinated: i.e., fluoride becomes an intrinsic part of its crystalline structure. This is postulated to combat decay by a combination of three possible mechanisms:
Enamel becomes more resistant to softening by acid from decay-forming bacteria;
Enamel develops an anti-bacterial quality, inhibiting growth of decay-forming bacteria; or
Enamel develops a smoother surface that resists the accumulation of decay-forming bacterial plaque.
Regardless of the mechanism or the efficacy of water fluoridation, its implementation required some assurance of safety, and therein lies the root of the controversy. Even before Jack D. Ripper declared (in the Stanley Kubrick movie Dr. Strangelove, 1964) that fluoridation was a "Communist conspiracy to sap and impurify all of our precious bodily fluids", fluoridation ran into heavy opposition, and still does. Beyond the paranoia of the conspiracy theorists, there are legitimate questions that must be addressed, as they must for every therapeutic measure.