Tooth mottling

B. Chronic effects. Minor overexposure in children under age 10 can cause tooth mottling. High chronic overexposure (more than 20 mg/day for more than 10 years) can cause skeletal fluorosis (osteosclerosis), ligament calcification, and increased bone density. 

Fluorosis affects the enamel of the tooth, causing it to become hypominera-lised. This is detected as visual changes in the opacity, and it is only in extreme cases that this leads to an adverse appearance as mottling of the tooth surface [86]. The severity of the discolouration depends on the dose of fluoride, its duration and timing of consumption. 

Fluoride ion tends to replace the isoelectronic ion OH- in solids. In particular, hydroxyapatite, Cas O OH, the chief constituent of tooth enamel, reacts slowly with aqueous fluoride to form fluoroapatite, which is harder and more resistant to tooth decay. The dental profession therefore advocates fluoride treatments at the time of regular dental checkups, and also (primarily to provide for the dental health of children) the presence of 0.7-1.0 ppm natural or added F in drinking water. Too much (>4 ppm) F in water, however, is acknowledged to cause mottling of teeth and bone sclerosis. Thus, the range of concentrations over which fluoride in public drinking water is considered to be beneficial is rather narrow. 

The toxic nature of fluoride ion, F, is not confined to its presence in HF. It is toxic in soluble fluoride salts, such as NaF. At relatively low levels, such as about 1 ppm, used in some drinking water supplies, fluoride prevents tooth decay. At excessive levels, fluoride causes fluorosis, a condition characterized by bone abnormalities and mottled, soft teeth. Livestock are especially susceptible to poisoning from fluoride fallout on grazing land as a result of industrial pollution. In severe cases, the animals become lame and even die. 

Ingestion > inhalation. At low levels mottling of tooth enamel. At high levels fluorosis—includes wide variety of health problems such as hyperparathyroidism, calcification of soft tissues, interference with collagen formation, severe skeletal deformity. 

The effect of fluoride in ptevenring dental caries was recognized when it was found that levels of tooth decay were low in regions of the world where the water supply naturally contained high levels of fluoride. In some regions, the levels of fluoride are so high that they cause a harmless mottling of the teeth called "fluorosis." Both the first set and the permanent set of teeth benefit from dietary fluoride. Water and other fluids account for most of our fluoride intake. 

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. 

This chapter describes how individuals with severe enamel fluorosis (mottled tooth enamel) became associated with fluoride in the public water supply and protection from dental caries. A comparison of caries experience with the fluoride content of public water supplies and enamel fluorosis in adolescents indicated that 1 pg fluoride/mL (1 part/million) in the water provides caries protection with minimal enamel fluorosis (sect. 1). One mechanism is the spontaneous isomorphic replacement of apatite s hydroxide anions with fluoride, which reduces enamel solubility. A second is fluoride-mediated inhibition of enolase, which retards bacterial acid production at teeth surfaces. These findings led to the use of fluoride in toothpastes, which provides better protection from caries at tooth surfaces than water fluoridation alone (sect. 2). The chapter concludes with a discussion of potentially harmful effects of fluoride ingestion (sect. 3). 

The fluoride ion can replace the hydroxide ion in a crystal without significantly altering its structure, an isomorphous ion replacement. Fluoride also affects the enzymes involved in enamel formation, causing mottled enamel, a severe example of enamel fluorosis. White opaque patches on the normally translucent enamel indicate mild fluorosis. Fluorosis is measured on a grade of 0-5 where 1 through 3 indicate an increased cover of opaque white patches on the tooth surface, and 4 and 5 indicate an increased mottling. The two worst affected teeth make up an individual s score. The community s index of fluoridation is the mean score for all individuals. As the natural or artificial fluoride concentration of the water supply increases to 1 ppm, the mean number of cavities in 10-12 year-old children decreases from 7 to 3. Above 1 ppm fluoride, caries does not decrease much more, but the index of fluorosis increases markedly. This is the reason why public water supplies are fluoridated to only 1 ppm and not more or less. 

Now as before, the various forms of tooth decay and osteoporosis each point at fluorine deficiency in humans as being a causative factor. In this respect, the fluoridation of public water supplies and use of fluorine-containing substances are recommended. Dental mottling is a sign of subtoxicity that is related to excessive fluoride intake. Fluorine concentrations below 0.3-0.5mgL indicate a risk of hypofluoric status, as a water level of 1.5 mg L can cause fluorosis, especially in regions with a hot climate... 

Stannous fluoride is a classic example of a compound that must be used in moderation. In small concentrations, it appears to be completely safe for human uses. In larger doses, it may have some health risks. For example, in concentrations of more than two parts per million, stannous fluoride (and other fluorides) may causes fluorosis, a mottling (brownish coloring) of the teeth and changes in bone composition. Individuals who work with pure stannous fluoride may also be at risk from exposure to its powder or dust. It is an irritant and may cause inflammation of the skin, eyes, or respiratory system. Symptoms may include coughing, wheezing, and shortness of breath. These effects do not occur, however, at the level at which stannous fluoride occurs in tooth care products. 

Chronic fluoride intoxication is more common and, since fluoride is concentrated in the hard tissues, the bones and teeth show the most obvious effects of fluorosis. Intake of excessive amounts of fluoride during tooth development results in mottled enamel which is characterized by the presence of scattered irregular white flecks. The permanent teeth are particularly susceptible. Towards the end of the last century this condition was found to be of common... 

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