FLUORIDE in water causes dental fluorosis. But how exactly? This was not known till now. Scientists from Japan and usa have identified the molecule in the cell that makes one susceptible to fluorosis. They hope their findings would lead to a drug for the ailment that has no cure. It will also benefit those suffering from dental caries and damaged enamel.

Millions of people, who drink water with high fluoride levels, are at risk of fluorosis. Excessive fluoride in drinking water weakens bones and discolours teeth. The symptom—discolouration—occurs first, at exposure to low levels of fluoride. Drinking fluoride free water helps avoid the problem [see below]. Also, a calcium, vitamins C, E and antioxidant-rich diet minimizes its adverse effects.

Disrupting enamel formation

Researchers from Forsyth Institute, Boston, usa and Tohoku University, Sendai, Japan studied the effect of fluoride on the formation of tooth enamel and found that it interfered with the process of making the enamel. The group studied molecular responses of cells exposed to fluoride.

They used ameloblasts, epithelial cells responsible for enamel formation and carried out experiments to see how fluoride affected the functioning of endoplasmic reticulum, a cell component that makes proteins. The proteins produced by the endoplasmic reticulum must be correctly folded and assembled before being transported to different parts of the cell for the enamel to remain healthy.

Ameloblasts were exposed to various levels of fluoride.

The amount of proteins, indicating endoplasmic reticulum stress, produced by the cells, was measured. In another experiment, mice were fed with water containing fluoride and their teeth were studied. The experiments showed that with increasing levels of fluoride, there was an increase in the endoplasmic reticulum stress.

Enamel, the hardest substance produced by the body, is vulnerable in the early stages of development. It is 96 per cent mineral and 4 per cent organic. Presence of fluoride during tooth formation increases the protein content and decreases mineral content. It does this by affecting the functioning of endoplasmic reticulum. Fluoride levels as low as 2.4 parts per million can lead to a softer and porous enamel. The researchers will now test chemicals that are known to reduce this stress. “We can establish a screening process to establish whether a person is susceptible to fluoride,” says John D Bartlett, the lead author of the study published in September issue of Environmental Health Perspectives.

The researchers now plan to copy the process of making the enamel in the lab to fill dental cavities and replace malformed enamel. According to Tilmann Wurtz of Cordelier Research Centre in Paris, the hypothesis needs to be tested in a model closer to real life.

“The knowledge of the behaviour of cells will improve understanding of tissue formation. We know that fluorosis is cause by too much fluoride, so the best remedy is already evident—to drink good quality water,” he said.

Fluoride water – Where does it spring from?

Fluoride is naturally present in rocks. It made its way into drinking water when people started using ground water instead of surface water. In the mid 1960s and 1970s when deep hand pumps were introduced, fluoride found its way into people’s homes. The extent of fluoride contamination of water in India varies from 1.0- 48.0 mg/l.

An estimated 62 million people, six million children included, are affected in India. The safe limit for fluoride is 1 mg/l in drinking water. Some toothpastes also contain fluoride. Besides fluorosis, exposure to fluoride can also result in brittle bones, renal toxicity, epithelial lung cell toxicity and reproductive defects. Levels from 0.8-1.2 mg/l are believed to be good for preventing tooth decay and strengthening bones. Levels above 1.5 mg/l lead to marks on the teeth and those above 10 mg/l lead to crippling skeletal fluorosis.

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