I blogged about fluoridation, having read an article by a nutritionist that cited conspiracy theorists. http://jdc325.wordpress.com/2009/02/28/briffa-on-fluoridation/

The Centre for Reviews and Dissemination at York University conducted a review of the evidence regarding flouridation. They have a webpage which tells us that they were unable to find reliable evidence regarding fluoridation and records their concern about the misrepresentation of their work.

From the executive review:

The evidence of a benefit of a reduction in caries should be considered together with the increased prevalence of dental fluorosis. The research evidence is of insufficient quality to allow confident statements about other potential harms or whether there is an impact on social inequalities.

Mark - Fluoride does harden the outer enamel of teeth but doesn't prevent tooth decay. Dentists find "fluoride bombs" which means an otherwise intact-looking tooth "explodes" open upon probing to reveal a hidden cavity - too small to appear on x-rays.

The CDC says that fluoride in enamel is not inversely related to tooth decay

Taken from wikipedia:

"Water fluoridation Main article: Water fluoridation

Water fluoridation is the controlled addition of fluoride to a public water supply in order to reduce tooth decay.[8] Its use in the U.S. began in the 1940s, following studies of children in a region where water is naturally fluoridated. It is now used for about two-thirds of the U.S. population on public water systems[9] and for about 5.7% of people worldwide.[10] Although the best available evidence shows no association with adverse effects other than fluorosis, most of which is mild,[11] water fluoridation has been contentious for ethical, safety, and efficacy reasons,[10] and opposition to water fluoridation exists despite its support by public health organizations.[12] As mentioned, fluoride primarily only helps teeth when it is in the mouth. After it is swallowed, it has minimal effect.

A 2000 systematic review of water fluoridation's effectiveness found that fluoridation was associated with a decreased proportion of children with cavities (the median of mean decreases was 14.6%, the range −5% to 64%), and with a decrease in decayed, missing, and filled primary teeth (the median of mean decreases was 2.25 teeth, the range 0.5 to 4.4 teeth). A more comprehensive 2007 review which used the 2000 review for its water fluoridation efficacy conclusions affirmed this result.[11]"

As someone who is involved in dentistry I cannot help but to suggest that fluoride has so much more benefit to offer than risk that I can only condone one argument against fluoridation of water supplies and that is - medication without consent. This is a sound ethical argument. However to consider that most people (in the western world perhaps) use fluoride toothpaste/mouthwash/salt etcetera out of choice currently and I presume would also choose to use fluoride water if it were available, is also to say that should they choose not to use it then many forms of bottled water are available. To deny water fluoridation to the most deprived in society, especially children, who are perhaps not going to be seeing dentists regularly and having their teeth lovingly cared for by a devoted parent, is extremely selfish, or perhaps merely misguided. Misguided by a very loud and generally ill-informed mob of anti fluoride campaigners. I can only thank the local authorities in Southampton, UK who overrode the protests and have pushed fluoridation forward. (http://www.southcentral.nhs.uk/fluoridation/)

Actually, the National Research Council (NRC) reported in 2006 that the maximum contaminant level Goal (MCLG) the EPA allows in the water supply - 4 mg/L - is too high to be protective of health. It took a panel of experts 3 1/2 years to evaluate hundreds of studies to come to that conclusion. The NRC did this at the request of the EPA. Oddly the EPA has yet to act upon this even though they are way over-do on the required re-assessment of fluoride. Scientists who know say the EPA management is fearful that they will have to make the politically unfavorable decision that would effectively have to kill fluoridation because the MCLG in water supplies should be zero, based on the science revealed in the NRC report.

Scientists who worked at the EPA in risk assessment say that the MCLG is the non-enforceable level by which any person can be harmed by fluoride. The NRC report reveals studies which show that fluoride, even at levels added to water supplies, can be especially harmful to thyroid patients and especially those with iodine deficiency which many Americans are.

The NRC also found that infants fed "optimally" fluoridated water puts them at increased risk of dental fluorosis (discolored teeth). This caused the American Dental Association and the Centers for Disease Control to advise that infant formula not be mixed with fluoridated water.

Clearly fluoridation is not safe for everyone.

Here in Basel, Switzerland, we used to have this but stopped because it seemed to be inefficient, with most of the fluorized water going directly to waste.
Instead we use fluorized salt. In '03 85% of swiss households used fluorized (and iodized) salt, so fluorizing the water supply wasn't necessary anymore, anyways. As far as a quick search on google reveals we still put iodine into our water supply and both into our salt. So far to only positive results.
The quacks are still screaming, however.

An interesting question. There appears to be only minor risks in the fluoridation of water (mainly for children's milk teeth and one Australian study found 'unclear' links to an increased cancer risk) compared to clear dental benefits. So far, all seems reasonable enough. But I'm personally a little concerned about the idea of fluoridating water, in spite of the potential health benefits. Here in France it is illegal (as it is in Sweden and the Netherlands) on mainly ethical grounds, i.e., you potentially have no choice in the matter, and it thus convenes the EU Human Rights laws.

That leads to the Precautionary Principle, that the burden of proof falls on those who advocate an action that may risk public health. In this case it is virtually impossible to guarantee that the introduction of fluoride into water is entirely without risk, mostly because fluoride is highly poisonous at certain dosages, and a poisonous dosage is not inconceivable as being erroneously (or maliciously) introduced to the water supply.

By 'poisonous dosage' I don't neccesarily mean that a glass of water might have you collapsing and grasping at your throat, but more that it may have long term negative effects on those already vulnerable, diabetics, people with kidney disorders, people prescribed lithium, anyone who drinks excessive amounts of water for whatever reason.

Internationally and historically speaking, one might have further cause for speculation. Water fluoridation was first implemented by the Nazis (and therefore remains banned in Germany under their anti-Nazi laws), and it used by the USA, UK, Ireland, Australia and Canada with one or two others. There seems to be a theme there! My main concern is that in the UK it gives more validity to the general apathy towards dentistry (the stereotype is quite accurate - it can take 6 months to get a dentist), while in France, for example, where there is no fluoridation, I know at least I can get up and go and see a dentist in 20 minutes, if I feel I have to.

answers can be found here http://www.quackwatch.org/03HealthPromotion/fluoride.html