For years a battle has gone on between advocates of fluoride and the detractors of the same. Those in the latter category say that fluoride is ineffective and not safe. There, however, seems to be little evidence to support the claims of the nay-sayers. A major concern among some dentists is the onset of dental flurosis from an overdose of fluoride. Dental flurosis can cause yellow to brownish stains on teeth which might call for porcelain veneers at some point, and may also cause pitting of teeth. The onset of dental flurosis typically occurs between the ages of 6 months and 5 years. It is even suggest that fluoride can lead to the development of brittle bones.
All of the above stated conditions stem from an overuse, or overdosing of fluoride, and it should be noted that, in moderation, fluoride is beneficial, not harmful. Kidshealth.org suggests that:
Scientific research continues to support the benefits of fluoride when it comes to prevention of tooth decay and its safety at current recommended levels of 0.7 to 1.2 ppm. Dramatic reductions in tooth decay in the past 30 years is attributed to fluoridation of the water supply, and parents and health professionals should continue to ensure that kids receive enough fluoride to prevent cavities.
As a parent, your main concerns with children should be monitoring the intake of fluoride, simply to make sure that it is not more than is needed. Otherwise, fluoride is a great tool in the fight against tooth decay.