Drinking water fluoridation

Dentifrices, more commonly called toothpastes, are a widely used source of fluoride for the majority of the population in the developed world. First introduced in the 1970s, fluoride-containing toothpastes accounted for over 90% of the market in the industrialised nations by the 1990s [151], Because not all countries fluoridate their drinking water, fluoridated toothpastes are, for many people in the world, the most important source of this element for oral health. 

M.J. Rudolph, M. Molefe, U.M.E. Chikte, Dental fluorosis with varying levels of fluoride in drinking water. Fluoride and fluorosis, The Status of S. Afr. Res., North West Province, 5, 1995. 

The administration of fluoride in drinking water at concentrations of approximately 1 ppm significantly reduces dental caries. The anticaries benefits are similar to those due to natural fluoride in drinking water. Fluoridated drinking water produces the following a 60% lower dental caries rate, a 75% decrease in the loss of 6-year molars, and a 90%i reduction in the incidence of proximal caries of the four upper anterior teeth. 

Thus most people, wherever they live, are likely to ingest some fluoride in their drinking water. Fluoride is also present in the diet most foodstuffs contain small amounts and a few are relatively rich sources. These include mackerel, salmon, sardines, some mineral waters, wines and tea. This latter is important since its fluoride content may be as much as 100 mg kg" of which up to 90% is extracted during infusion, and quite large volumes of tea may be drunk each day. 

While nobody can guarantee the safety of any human measure under all circumstances, the safety of the adjustment of drinking water fluoride to about 1 ppm is supported by so large and so manifold scientific material and clinical data that any health hazard with this measure is extremely improbable. Specific claims of such hazards have been few and inadequately supported. 

Serum and drinking water fluoride levels were estimated by ion-selective electrodes. Both the serum and drinking water fluoride levels were significantly higher in patients wi osteosarcoma as compared to controls. These results suggest a link between fluoride exposure and osteosarcoma. 

The presence of fluorine as a soluble fluoride in drinking water to the extent of 2 ppm may cause mottled enamel in teeth, when used by children acquiring permanent teeth in smaller amounts, however, fluorides are added to water supplies to prevent dental cavities. 

The concentration of fluoride in drinking water may be determined indirectly by its ability to form a complex with zirconium. In the presence of the dye SPADNS, solutions of zirconium form a reddish colored compound, called a lake, that absorbs at 570 nm. When fluoride is added, the formation of the stable ZrFe complex causes a portion of the lake to dissociate, decreasing the absorbance. A plot of absorbance versus the concentration of fluoride, therefore, has a negative slope. 

Fluorides. Most woddwide reductions in dental decay can be ascribed to fluoride incorporation into drinking water, dentifrices, and mouth rinses. Numerous mechanisms have been described by which fluoride exerts a beneficial effect. Fluoride either reacts with tooth enamel to reduce its susceptibihty to dissolution in bacterial acids or interferes with the production of acid by bacterial within dental plaque. The multiple modes of action with fluoride may account for its remarkable effectiveness at concentrations far below those necessary with most therapeutic materials. Fluoride release from restorative dental materials foUow the same basic pattern. Fluoride is released in an initial short burst after placement of the material, and decreases rapidly to a low level of constant release. The constant low level release has been postulated to provide tooth protection by incorporation into tooth mineral. 

F H. T. Dean et al. put the correlation between decreased incidence of dental caries and the presence of fluoride ions in drinking water on a quantitative basis... 

Stannous fluoride, a compound of tin and fluorine, is much less dangerous. It is added to drinking water and toothpaste to strengthen the enamel in the teeth of the user. Another compound of fluorine is teflon, a plastic made of carbon and fluorine, which is used in kitchenware. The fluorine-containing compound freon is used in air-conditioners and refrigerators, and is harmless. 

CCP in milk is mentioned in connection with casein above (Section VI.C). Fluorapatite is a major constituent of phosphate rocks, and a constituent, probably important, of human tooth enamel for those whose drinking water contains significant amounts of naturally occurring or added fluoride. Fluorapatite is significantly less soluble than hydroxyapatite - the relationship between the solubilities of fluorapatite and hydroxyapatite parallels (but is much less extreme than) that between calcium fluoride (Ksp — 3.9 x 10 11 mol3 dm-9) and calcium hydroxide (Ksp = 7.9 x 10 6 mol3 dm 9). Calcium diphosphate, Ca2P207, is believed to be the least soluble of the calcium phosphates. 

The potentiometric method also surpasses the others for speed, simplicity, precision and accuracy as indicated in Table 12.1. Furthermore, it is particularly suited to the continuous monitoring of fluoride levels in drinking water. The spectrophotometric methods are lengthy because of the time required to develop a stable colour (up to 1 hour), the alizarin red-S complex being especially poor in this respect. It was noted, however, that for the three bleaching methods (1-3) the rate of change of absorbance by the blank closely followed that of solutions containing fluoride, i.e. the difference between the blank and a sample absorbance is nearly constant. 

The fluoride content of the heart appeared to increase in old mice fed the low Ca diet and fluoride feeding caused an increase in the level of the hearts of old mice fed high or low Ca diet. When male or female mice were supplied drinking water containing 10 mg/L fluoride, the levels in the soft tissues including heart and kidney were, however, undetectable at 24 months of age (25). This could be due to limited sensitivity of the method used by these investigators. 

Fluoride, Fluoride Is contained In water and In the diet (22,23) Also, fluoride stabilizes the bone crystal (24) and has been shown to decrease bone resorption (25), For these reasons, fluoride has been recommended for the treatment for osteoporosis (26-28), The Importance of the role of fluoride on maintaining the normal bone structure Is also Indicated by a survey which showed that the Incidence of osteoporosis was lower In naturally high fluoride areas than In areas where the fluoride content of the drinking water was low (29) This observation would Indicate that the Intake of certain amounts of fluoride throughout life may be necessary for the maintenance of the normal skeleton, and that fluoride may protect the skeleton from the development of bone loss which leads to osteoporosis with advancing age, particularly In females. 

Most foods and drinking waters contain enough fluoride to result in the incorporation of significant amounts of fluoride into this mineral whereby the solubility decreases. Therefore, the system hydroxyapatite-fluorapatite is primarily of importance for the prevention of dental caries. However, in this context its theoretical treatment is important for geochemists who may be confronted with so-called subregular solid solutions. 

Frencken JE, Truin GJ, Van t Hof MA, Konig KG, Kahabuka FKA, Mulder J and Kalsbeek H (1991) Fluoride in drinking water and caries progression in a Tanzanian child population. Commun Dent Oral Epidemiol 19,180-181. 

Sodium fluoride (NaF), in the concentration of one ppm, is added to municipal drinking water to help reduce tooth decay. It is also used as an insecticide, fungicide, and rodenticide, as well as in the manufacture of adhesives, disinfectants, and dental products. 

Poisonous fluoride salts are not toxic to the human body at the very low concentration levels used in drinking water and toothpaste to prevent dental decay. 

Three limited early carcinogenicity bioassays in three different strains of mice by oral administration of sodium fluoride (NaF) revealed no exceptional tumor incidences. A subsequent NTP study reported equivocal evidence of carcinogenicity based on osteosarcomas in 4 of 80 male rats administered 175 ppm NaF in the drinking water for 2 years. No evidence of carcinogenicity was found in another... 

No adverse effects on fetal development were found in rats or rabbits administered fluoride in the drinking water during gestation. ... 

---