Skeletal fluorosis is a bone disease caused by excessive accumulation of fluoride in the bones. In advanced cases, skeletal fluorosis causes painful damage to bones and joints. Symptoms are mainly promoted in the bone structure. Due to a high fluoride concentration in the body, the bone is hardened and thus less elastic, resulting in an increased frequency of fractures. Other symptoms include thickening of the bone structure and accumulation of bone tissue, which both contribute to impaired joint mobility. Ligaments and cailage can become ossified. Most patients suffering from skeletal fluorosis show side effects from the high fluoride dose such as ruptures of the stomach lining and nausea. Fluoride can also damage the parathyroid glands, leading to hyperparathyroidism, the uncontrolled secretion of parathyroid hormones. These hormones regulate calcium concentration in the body. An elevated parathyroid hormone concentration results in a depletion of calcium in bone structures and thus a higher calcium concentration in the blood. As a result, bone flexibility decreases making the bone more susceptible to fractures Mechanism of action The best way to view the mechanism of action by which fluorine breaks down bones and causes skeletal fluorosis is in a stepwise fashion. Fluoride enters the body by two paths: Ingestion or respiration. Both paths lead to corrosion of exposed tissue in high concentrations. Since the most likely form of fluoride to enter the body is hydrogen fluoride (HF) gas, this is what stas the process. Exposed tissues will be utilized by HF in neutralization reactions. This will leave F- free to pass fuher into the body. It reacts with the concentrated HCl in the stomach to form the weak acid, HF. This compound is then absorbed by the gastro-intestinal tract and passes into the liver the poal vein. Since elemental F is one of the strongest oxidizers currently known, the anion F- is immune to phase 1 metabolic reactions, which are generally oxidation reactions, in the liver. These reactions are the body's first line of defense to biotransform harmful compounds into something more hydrophilic and more easily excreted. The HF is now free to pass into the blood stream and be distributed to all tissues including bones. Bones are largely composed of Ca compounds, paicularly carbonated hydroxyapatite (Ca 5(PO 4) 3(OH)); the reaction of Ca2+ ions and HF forms an insoluble salt, CaF 2. This salt must be cleared by the body, which concomitantly leaches out some of the calcium that would be pa of the bone matrix. This process results in increased density, but decreased strength in bones As of now, there are no established treatments for skeletal fluorosis patients. However, it is reversible in some cases, depending on the progression of the disease. If fluorine intake is stopped, the amount in bone will decrease and be excreted urine. However, it is a very slow process to eliminate the fluorine from the body completely. Minimal results are seen in patients. Treatment of side effects is also very difficult. For example, a patient with a bone fracture cannot be treated according to standard procedures, because the bone is very brittle. In this case, recovery will take a very long time and a pristine healing cannot be guaranteed. However, fuher fluorosis can be prevented by drinking defluoridated water. It is recently suggested that drinking of defluoridated water from the ''calcium amended-hydroxyapatite'' defluoridation method may help in the fluorosis reversal. Defluoridated water from this suggested method provides calcium-enriched alkaline drinking water as generally fluoride contaminated water has a low amount of calcium mineral and drinking alkaline water helps in eliminating the toxic fluoride from the body Ref Davidson 23rd edition pg 715