[saurik]

I was under the impression that no one has ever shown that drinking fluoride does much for your teeth: it doesn't have a systemic effect; if you soak your teeth in concentrated fluoride that helps (though we might be overdoing it now in the US for children: tons of cases of teeth with floirinosis; I have some friends who clearly have this problem... but for adults it is great), but the momentary contact of the extremely small concentration of flouride in drinking water can only do harm as it ends up in other parts of your body... and we also know it does harm, the only question is whether there is enough in your water for the harm to be noticeable.