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Witten. Fluoride protects the teeth from tooth decay. However, an overdose of the mineral can interfere with the formation of the tooth enamel. The substance disrupts the calcium and energy metabolism in the enamel-forming cells in excess, scientists report in the journal “Science Signaling”. This can lead to dental fluorosis, in which white to brownish spots or stripes form on the tooth enamel. According to dentist Stefan Zimmer from the University of Witten / Herdecke, there are hardly any problems with dental fluorosis in Germany. Meanwhile, fluoride is an essential factor in preventing tooth decay.
Fluoride: when does oversupply occur?
Zimmer believes that there is no reason to worry about getting too much fluoride in food or drinking water in Germany. If tooth fluorosis occurs in Germany due to over-supply, it is usually a cosmetic problem for which there are treatment options, says Zimmer. So it is possible to let plastic flow into the affected areas or to carefully sand and seal the areas. An oversupply can occur, for example, if children take fluoride tablets in addition to fluoride toothpaste. Experts advise parents to choose one of the two approaches.
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Dentistry: Reasons for mineralization disorders are sometimes unclear
Another dental mineralization disorder, molar incisive hypomineralization, or MIH for short, has played a greater role in dentistry than dental fluorosis for several years. There is also discoloration on the teeth, especially on the molars and – less pronounced – on the incisors. Externally, MIH is similar to dental fluorosis, but fluoride does not play a role in its formation, explains Zimmer. The causes are unclear, including medication, environmental toxins and a vitamin D deficiency.
Doctors recommend fluoride toothpaste for children
According to current dental recommendations, children should be brushed with fluoride toothpaste every day from the breakthrough of the first milk tooth. Experts advise brushing toothpaste with 1000 ppm fluoride (parts per million) twice a day in the first two years of life with a rice grain-sized amount. From the second birthday onwards, a pea-sized amount should be used. The fluoride is embedded in the tooth enamel and makes it harder. It protects the teeth from enamel-damaging acids and thus from caries. “Fluoride is the decisive factor in the prevention of tooth decay,” explains Zimmer from the Chair for Dental Preservation and Preventive Dentistry. “Brushing with a good fluoride toothpaste prevents about 40 to 50 percent of all carious lesions.”
Why does a large amount of fluoride damage the teeth?
It has long been known that too much fluoride can damage teeth and cause tooth fluorosis. This happens during the formation of the enamel, which is completed at around six years. Discoloration becomes visible when the permanent teeth break through. With pronounced fluorosis, the tooth can become more susceptible to tooth decay. Exactly what exactly happens in the enamel was largely unclear. The researchers led by Francisco Aulestia from the New York University College of Dentistry have now investigated what happens in rat enamel-forming cells.
They added a high dose of fluoride to the cells. This roughly corresponded to that which people in regions with many cases of fluorosis ingest. As a result, there were disorders in the calcium metabolism in the cells. Calcium is an essential building block for stable teeth.
Scientists find out how fluorosis develops at the cellular level
Specifically, the scientists found that the absorption and storage of calcium in the so-called endoplasmic reticulum, a cell area that, in addition to calcium storage, performs numerous functions in the cell metabolism. Genetic analyzes showed that the activity of genes associated with stress reactions in this cell area increased. The energy production in the mitochondria – the power plants of the cells – was also disrupted by the fluoride overdose. The researchers did not find these reactions in kidney cells.
The results show how fluorosis develops at the cellular level, the researchers write. “If the cells are supposed to make enamel that contains a lot of calcium, but are under stress due to the high fluoride content in the processing of calcium, this will affect the formation of the enamel crystals and affect the mineralization,” explains Rodrigo Lacruz , one of the scientists involved.
Problematic: In the United States, drinking water is mixed with fluoride
Fluorosis is a much bigger problem in the United States than in Germany. According to the researchers, around 30 percent of the population are affected. “In Germany you can assume about 1.5 percent,” says Zimmer. The main reason for the difference is that in the US – and many other countries – drinking water is mixed with fluoride. The children’s toothpastes there also had a higher fluoride content.
Fluoride also enters the body through food. There are traces of fluorides in wholegrain products, nuts, black and green tea, mineral water and sea fish. Small amounts of fluoride are added to table salt and drinking water naturally also contains fluoride – the content fluctuates with regional geological conditions.
RND / dpa
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