<unk>  or<unk>  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<unk>  in the diet. Common dietary sources of<unk>  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<unk>  poisoning has given rise to some controversy.<unk>  is not considered to be an essential nutrient, but the importance of<unk> s for preventing tooth decay is well-recognized, although the effect is predominantly topical. Prior to 1981, the effect of<unk> s was thought to be largely systemic and preeruptive, requiring ingestion.<unk>  is considered essential in the development and maintenance of teeth by the American Dental Hygienists' Association.<unk>  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<unk>  were first believed to have been seen in 1902 when<unk>  in high concentrations was found to stain teeth and prevent tooth decay.<unk>  salts, particularly sodium<unk>  (NaF), are used in the treatment and prevention of osteoporosis. Symptoms such as fractured hips in the elderly or brittle and weak bones are caused due to<unk>  in the body.<unk>  stimulates bone formation and increases bone density, however bone with excess<unk>  content has an abnormal structure resulting in increased fragility. Thus<unk>  therapy results in large increases in bone mineral density but the effect on fracture rates, while positive, is small. Disputes over the essentiality of<unk>  date back to the 19th century, when<unk>  was observed in teeth and bones. In 1973 a trial found reduced reproduction in mice fed<unk> -deficient diets, but a subsequent investigation determined that this was due to reduced iron absorption.
Fluorine deficiency
Boron deficiency 
Chromium deficiency
Fluoride toxicity
Selenium deficiency
Biotin deficiency
Thiamine deficiency
Iodine deficiency