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Salt Fluoridation

Oral disease is a significant burden to all countries of the world and is the fourth most expensive disease to treat. Although dental health has improved dramatically across many of the world’s populations, there are still huge problems with dental caries (tooth decay and cavities) in many sections of society, particularly the underprivileged. While steps can be taken to improve general education about oral care and hygiene, research and practical experience have shown that dental caries can be prevented most effectively through the establishment of fluoride programmes.

Fluoride controls caries effectively because it acts in several different ways. When present in biofilm on the teeth and saliva, it hastens the remineralisation of incipient enamel lesions, a healing process before cavities become established. Fluoride also interferes with glycolysis, the process by which cariogenic bacteria metabolize sugars to produce acid. In higher concentrations, it has antibacterial effects on cariogenic and other bacteria.

The Sixtieth World Health Assembly in 2007 urges for those countries without access to optimal levels of fluoride, and which have not yet established systematic fluoridation programmes, to consider the development and implementation of fluoridation programmes, giving priority to equitable strategies such as the automatic administration of fluoride, for example, in drinking-water, salt or milk, and to the provision of affordable fluoride toothpaste.

Many reports on a caries-preventive effect of fluoride when added to salt for human consumption have been published. Under favorable conditions, the cariostatic effectiveness is equivalent to that of water fluoridation which was, and under certain condition still is, the classical method of preventing caries in entire populations. Addition of fluoride to salt controls caries effectively but it does not have the potential of eliminating the disease.

Salt fluoridation should be considered where water fluoridation is not feasible for technical, financial or sociocultural reasons. One of the objections of water fluoridation is that it limits consumer\rquote s choice. If the public water supply is fluoridated, a consumer has few practical alternatives other than to purchase bottled drinking water that does not contain fluoride. One of the attractions of fluoridated salt is that it can be sold alongside a non-fluoridated alternative. When most salt for human consumption is fluoridated, the effectiveness of salt fluoridation approximates that of water fluoridation. In eight European countries there are national legal regulations, or salt producers have obtained individual authorisations, for the production and marketing of fluoridated edible salt : Austria, Czech Republic, France, Germany, Romania, Slovakia, Spain, Switzerland. The Canton of Zurich was the first political unit world-wide to authorize the sale of salt with fluoride in 1955.

Sodium and potassium fluoride are used for the fluoridation of household salt. Addition of fluoride is carried out either by the wet or the dry process. Qualitatively good fluoridated salt can be produced by using either method. In the wet process, a solution of potassium fluoride is mixed homogeneously with the salt. For the dry mixture, only sodium fluoride with a small grain size is suitable. Apart from mixing methods used by the larger salt manufacturers, there are low-cost solutions for very small producers. The concentrations of fluoride in salt used around the world range from 90 ppm to 350 ppm. Concentration of fluoride in European salts is mostly of around 250 ppm. The fluorides are based on natural resources (Fluorite, Fluorapatite), which are mined in China, Mexico and Namibia.

Depending on whether fluoridated salt is manufactured in a continuous or batch process and on whether the fluoride is added as a solution or in dry form, a plant-specific testing plan must be drawn up for the implementation of quality monitoring. Three well-established testing methods which have been validated in interlab studies are available to determine the fluoride content in food grade salt:

• EuSalt/AS 017: Determination of fluorides – Potentiometric method
• EuSalt/AS 018: Determination of anions – High performance ion chromatography (HPLC)
• EuSalt/AS 010: Determination of fluorides – SPADNS photometric method

In practice, the potentiometric method (“fluoride sensitive electrode”) has proven to be a simple, accurate and comparable low-priced process and is widely used.