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.
Cracked tooth syndrome (CTS) is where a tooth has incompletely cracked but no part of the tooth has yet broken off. Sometimes it is described as a greenstick fracture. The symptoms are very variable, making it a notoriously difficult condition to diagnose. Classification and definition
Cracked tooth syndrome could be considered a type of dental trauma and also one of the possible causes of dental pain. One definition of cracked tooth syndrome is "a fracture plane of unknown depth and direction passing through tooth structure that, if not already involving, may progress to communicate with the pulp and/or periodontal ligament." Signs and symptoms
The reported symptoms are very variable, and frequently have been present for many months before the condition is diagnosed. Reported symptoms may include some of the following:

Sharp pain when biting on a certain tooth, which may get worse if the applied biting force is increased. Sometimes the pain on biting occurs when the food being chewed is soft with harder elements, e.g. seeded bread. "Rebound pain" i.e. sharp, fleeting pain occurring when the biting force is released from the tooth, which may occur when eating fibrous foods. Pain on biting
Pain when grinding the teeth backward and forward and side to side. Sharp pain when drinking cold beverages or eating cold foods, lack of pain with heat stimuli. Pain when eating or drinking sugary substances.