Fluoride or fluorine deficiency is a disorder which may cause increased dental caries (or tooth decay, is the breakdown of dental tissues by the acidic products released by the "bacterial fermentation of dietary carbohydrates.") and possibly osteoporosis (a bone disorder which leads to a decrease in bone mass, and an increase in bone fragility),  due to a lack of fluoride in the diet. Common dietary sources of fluoride include tea, grape juice, wine, raisins, some seafoods, coffee, and tap water that has been fluoridated. The extent to which the condition truly exists, and its relationship to fluoride poisoning has given rise to some controversy. Fluorine is not considered to be an essential nutrient, but the importance of fluorides for preventing tooth decay is well-recognized, although the effect is predominantly topical. Prior to 1981, the effect of fluorides was thought to be largely systemic and preeruptive, requiring ingestion. Fluoride is considered essential in the development and maintenance of teeth by the American Dental Hygienists Association. Fluoride is also essential as it incorporates into the teeth to form and harden teeth enamels so that the teeth are more acid resistant as well as more resistant to cavity forming bacteria. Caries-inhibiting effects of fluoride were first believed to have been seen in 1902 when fluoride in high concentrations was found to stain teeth and prevent tooth decay.Fluoride salts, particularly sodium fluoride (NaF), are used in the treatment and prevention of osteoporosis.
There are a number of sources of fluoride, these include:

Water
In Australia fluoride occurs naturally within water supplies, at a concentration of approximately 0.1 mg/L. However, this number varies amongst different populations, as specific fluoridated communities exceed this amount, ranging from 0.6 to 1.0 mg/L of fluoride present. The process of incorporating more fluoride into water systems is an affordable mechanism that can provide many beneficial effects in the long term. Dentrifices
Fluoride toothpaste came into production in the 1890s, after its benefits were investigated. This product has become available to most industrialised countries, and within Australia accounts for "90% of total toothpaste purchased". Fluoride supplements
Fluoride supplements were first recognised and highly suggested by health professionals, in areas where the practice of fluoridating water was not accepted. This practice is recommended for individuals, primarily children (who are at a greater risk of caries) in low-fluoride areas. Dietary recommendations
The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for some minerals in 1997. Where there was not sufficient information to establish EARs and RDAs, an estimate designated Adequate Intake (AI) was used instead. AIs are typically matched to actual average consumption, with the assumption that there appears to be a need, and that need is met by what people consume. The current AI for women 19 years and older is 3.0 mg/day (includes pregnancy and lactation). The AI for men is 4.0 mg/day. The AI for children ages 1–18 increases from 0.7 to 3.0 mg/day.