Tooth decay, incidence

A high sucrose diet promotes decay.11 While most people have some trouble with tooth decay, 1 or 2 per thousand remain totally free of caries and seem to be immune. Many factors must affect resistance to caries. For example, individuals vary in the kinds and numbers of bacteria present on teeth and in the structure of tooth enamel.0 Addition of fluoride ion to water supplies at a level of lppm (0.05 mM) is generally believed to reduce the incidence of tooth decay. However, caries has been declining in many developed countries at rates that are the same for water with or without fluoride.p q If teeth escape caries periodental disease, caused by bacteria, is often a major problem for older people.1... 

Figure 13.2 shows how the incidence of tooth decay amongst 12-year-old children has declined over recent years, despite a significant increase in their consumption of soft drinks. 

Other important inorganic compounds of fluorine include uranium hexafluoride, UF6, a volatile substance that was used to separate 238U from the fissionable 235U by gaseous diffusion in the Manhattan Project. Sodium fluoride, NaF, is often added to drinking water and to toothpaste in order to reduce the incidence of tooth decay. 

A fluoride level greater than about 1.5 ppm does not significantly decrease the incidence of tooth decay, but does increase the occurrence and severity of mottling. 

Many studies over the last 50 years have established that addition of fluoride to drinking water reduces the incidence of tooth decay, and more than 60% of the U.S. population now uses fluoridated water. Clinical studies from 1950 to 1980 in 20 different countries found that adding fluoride to community water supplies, within the interval 0,7 mg to i.2mg/L, reduced the incidence of caries by 40% to 50% in primary (infant) teeth and by 50% to 60% in permanent teeth. The subject is controversial and there is opposition to mass medication with fluoride. Reviews of the benefits and the risks associated with the use of fluoride are avaflable. "-" " "... 

Sodium fluoride, NaF, is often added to drinking water and to toothpaste in order to reduce the incidence of tooth decay. 

Salivary glands A wide spectrum of salivary gland complaints, ranging from mild transient discomfort to permanent xerostomia and tooth decay, have been described after the administration of radioiodine. In a retrospective study of 262 patients who underwent remnant ablation with I there were significant salivary gland adverse reactions in 40%. In most cases the reactions were transient, and after a median follow-up of 7 years the incidence of persistent adverse reactions was only 5% [23. ... 

One way to help prevent tooth decay is by using fluoride. Fluoride reacts with hydroxyapatite in a doubledisplacement reaction. It displaces the 0H group in hydroxyapatite to produce fluorapatite, Ca5(P04)3F. Studies show that calcium fluorapatite is about 20% less soluble than hydroxyapatite in acid. Therefore, fluoride lowers the incidence of tooth decay. 

In countries where sugar intake is low, such eis China and Ethiopia, the incidence of caries is low, while in areeis where the intake of sugar is high, such eis Australia, Hawaii, and French Fblynesia, there is a very high incidence of tooth decay. 

The fluoride ion, at proper levels of intake, assists in the prevention of dental caries. When children under 9 years of age consume drinking water containing 1 part per million of fluorine, the teeth have fewer dental caries in childhood, adolescence, and throughout life. This has led to the fluoridation of water supplies in many countries. Fluoridation of water supplies to bring the concentration of fluoride to 1 ppm (one part of fluorine to a million parts of water) has proved to be safe, economical, and an efficient way to reduce tooth decay—a highly important public health measure in areas where natural water supplies do not contain this amount. Extensive medical and public health studies have clearly demonstrated the safety and nutritional advantages that result from fluoridation of water supplies. In communities in which fluoridation has been introduced, the incidence of tooth decay in children has been decreased by 50% or more. 

The fluoride ion can exchange for hydroxyl in the crystal structure of apatite, a main component of skeletal bone and teeth. This stabilizes the regenerating tooth surface. Fluoride is available from saliva and may also be released from dental plaque at low pH. Initially, benefit was considered solely to be for the erupting teeth of children, but topical effects on adult teeth are now also thought to reduce decay. There is some initial evidence from small studies that pharmacological doses of fluoride may reduce the incidence of bone fracture in patients with osteoporosis. However, a metaanalysis of fluoride therapy from 11 controlled studies on 1429 subjects found that although this increased lumbar bone density, the incidence of vertebral fractures was not significantly decreased. ... 

The problem of dental decay is certainly a formidable one and can only be mentioned in passing here. Local factors may be of primary importance, but the role of the resistance of the tooth should not be minimized. May Mellanby saw some decrease in the incidence of caries... 

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