Health Effects of Ingested Fluoride (1993) / Chapter Skim
Currently Skimming:
2 DENTAL FLUOROSIS
2 DENTAL FLUOROSIS
Pages 19-50
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 19... ...
teeth to absorb fluoride into the enamel's crystalline lattice, however, rapidly diminishes as the enamel matures (Weatherell et al., 1977~. As a result, the amount of fluoride in dental enamel does not increase with age to nearly the same extent as in bone.
|
From page 20... ...
Enamel fluoride concentrations of this order have no adverse impact on oral health; indeed, the presence of fluoride in the crystalline lattice of dental enamel can only increase the enamel's resistance to dissolution in decaycausing acids. When drinking water contains naturally occurring fluoride at 5-7 mg/1= (much higher than recommended)
|
From page 21... ...
post-eruptive effects of fluoride, it became evident by the mid-1970s that a high concentration of enamel fluoride could not by itself explain the extensive reductions in caries that fluoride produced (Levine, 1976~. As clescribed earlier, enamel fluoride concentrations at a depth of 2 Am average I,7004,XOO ppm, depending on age and fluoride exposure.
|
From page 22... ...
The cariogenic bacterium Streptococcus mutans has been shown to become less acidogenic through adaptation to an environment where it is regularly exposed to low concentrations of fluoride in drinking water or to higher concentrations in toothpastes and mouth rinses (Rosen et al., 1978; Bowden, 1990; Marquis, 1990~. It is plausible, though not confirmed, that this ecological adaptation reduces the cariogenicity of S
|
From page 23... ...
This process has been well-illustrated in animal studies. When rats were given various concentrations of fluoride in their drinking water over a 5-week period, no differences were found in the protein content of fluorotic enamel and control enamel during the secretory phase of enamel formation (Den Besten, 1986~.
|
From page 24... ...
Early research indicated that the development of fluorosis in the continuously growing rat incisor was associated with occasional "spikes" in plasma fluoride concentrations, produced by daily injections, that raised the plasma fluoride concentration above a presumed threshold value (Angmar-Mansson et al., 1976; Myers, 1978~. Later research confirmed that finding (Angmar-Minsson and WhitforcI, 1982)
|
From page 25... ...
The shorter maturation period for primary teeth, adcled to lower fetal blood fluoride concentrations cluring their prenatal clevelopment, is probably the main reason why fluorosis in primary teeth is unusual outside areas of high-fluoride ingestion. DIAGNOSTIC ISSUES IN DENTAL FLUOROSIS Clinical diagnosis of fluorotic lesions has been plagued from the earliest studies by the fact that not all mottling of dental enamel is caused by fluoride.
|
From page 26... ...
Most cases of dental fluorosis are probably identified correctly by experienced examiners, but high and low population prevalences and individual cases have been reported that are incompatible with the fluoride histories. In such instances, the likelihood of misclassification seems strong.
|
From page 27... ...
and the trends in prevalence of "mottling" since the introduction of fluoride toothpastes (weeks, 1990~. Even though the problem of misclassifying dental fluorosis is recogn~zed during clinical assessments, determination of risk factors for fluorosis seems more likely to be successful when attempts are made to measure the condition directly.
|
From page 28... ...
fluoride concentrations that were similar to those in normal enamel (Richards et al., 1989~. The TF index might be too sensitive in those categories, which slider only slightly in their clinical appearance, for purposes other than analytical epidemiology (CIarkson, 19891.
|
From page 29... ...
In this review, we attempt to pool results but focus comparisons on prevalence and broad categories of "mild to very mild" and "moderate to severe." DENTAL F.LUOROSIS AND FLUORIDE INTAXE Dean's initial research established I.0 mg/L as the approximate concentration of fluoride in drinking water that best preventer] caries while keeping unsightly dental fluorosis to a minimum (Dean, 1942)
|
From page 30... ...
The range of 0.7-~.2 mg/L was established after a series of elegant studies in the 1950s that related fluoride concentrations in drinking water to fluorosis prevalence and severity in different climatic regions in the United States (Galagan, 1953; Galagan and Lamson, 1953; Galagan and Vermillion, 1957; Galagan et al., 1957~. The results of those studies were confirmed by further research a decade later (Richards et al., 1967~.
|
From page 31... ...
If all fluoride intake comes from drinking water, that dose for a child weighing 10 kg (an average I-yearold) would be ingested in 0.5-0.7 ~ of water fluoridated at I.0 mg/~.
|
From page 32... ...
In Kenya, fluoride concentrations of over 40 mg/L have been recorded in drinking water; in one study, over 20% of 1,290 boreholes in the Great Rift contained fluoride at more than 5 mg/L (Manji and Kapila, 1986a)
|
From page 35... ...
Prevalence of fluorosis can be seen to be directly related to fluoride concentration of drinking water up to approximately 4.0 mg/L, after which it tended to level out. Moderate-tosevere dental fluorosis began to be seen at about I.9 mg/L, and its prevalence rose with increasing fluoride concentrations.
|
From page 36... ...
0.4 0.9 1.3 1.9 2.2 2.6 3.9 4 4.4 7.6 Water Fluoride Concentrations FIGURE 2-2 Prevalence (percent) and seventy of dental fluorosis in 10 communities in the United States in the 1930s and 1940s by fluoride concentration (mg/L)
|
From page 37... ...
That reduction is largely attributable to an increase in fluorosis in nonfluoridated areas, where fluoride supplements, beverages processed with fluoridated water, and inadvertent swallowing of fluoride toothpaste represent sources of fluoride that were not present in the 1930s. As can be inferred from the ranges of prevalence already given, the extent of dental fluorosis in a community cannot be estimated from water fluoride concentrations alone.
|
From page 38... ...
The inconsistencies between dental fluorosis prevalence and water fluoride concentrations, seen in Figure 23, are difficult to explain. Even though examiner variability is likely to be a factor, the inconsistencies cannot be attributed solely to those variations because the inconsistencies are seen in most series of that kind (e.g., Dean's data in Figure 2-2)
|
From page 39... ...
Overall, dental fluorosis prevalence was noticeably higher at the lower fluoride concentrations than Dean had recorded but differed little at 3-4 times the optimal concentration. Moclerate-to-severe fluorosis might be even less prevalent, according to these data, than Dean recorded about 50 years earlier.
|
From page 40... ...
4.3 5 FIGURE 2-5 Prevalence (percent) and severity of dental fluorosis since 1980 for selected communities in the United States with above-recommended fluoride concentrations in drinking water.
|
From page 41... ...
Those sources make it difficult to estimate fluoride exposure; they represent a confounding factor in studies of the relation between fluoride exposure and dental fluorosis. RISK FACTORS IN DENTAL FLUOROSIS Dental fluorosis is a function of total fluoride intake during critical dental developmental periods, and in modern conditions, fluoride is ingested from numerous sources in addition to drinking water.
|
From page 42... ...
One such risk factor is ob viously a high fluoride concentration in drinking water (Szpunar and Burt, 19881; even minor adjustments in water fluoride concentrations can lead to significant changes in the prevalence of clinically detectable fluorosis (Evans and Stamm, 199Ib)
|
From page 43... ...
believe that the best approach to stabilizing the prevalence and severity of dental fluorosis is to control fluoride ingestion from foods, processed beverages, and dental products rather than reduce the recommended concentrations of fluoride in drinking water. A large number of studies have concluded that fluoride supplements are a risk factor for dental fluorosis (Holm and Andersson, 1982; Suck ling and Pearce, 1984; Hellwig and Klimek, 1985; Bohaty et al., 1989; Dooland and Wylie, 1989; Kumar et al., 1989; Larsen et al., 1989;
|
From page 44... ...
Fluoride in foods and beverages processed with fluoridated water has long been suspected as a risk factor but has not been clearly demonstrated. Unexpectedly high fluoride concentrations in particular foods and beverages (Clovis and Hargreaves, 1988; Burt, 1992; Pang et al., 1992)
|
From page 45... ...
THE RELATION BETWEEN DENTAL F1UOROSIS AND CARIES Dean's studies of this relation in the 1930s showed a sharp reduction in caries prevalence when communities were ranked from the lowest water fluoride concentrations (virtually zero) to approximately ~ .0 mg/~.
|
From page 46... ...
The data also show fairly consistently that a small, though measurable, proportion of a population exhibits moderate-to-severe dental fluorosis with .-2.0 times the optimal concentration of fluoride in drinking water, and this proportion generally increases with increasing concentrations of fluoride. However, the data are not consistent enough to permit a firm definition of the relation between moderate-to-severe dental fluorosis and water fluoride concentrations.
|
From page 47... ...
Source: Eklund et al., 1987. drinking water is the only source of fluoride, the evidence supports the conclusion that water fluoridation at currently recommended concentrations results in prevalence of mild-to-very-mild dental fluorosis of about 10% and very little severe fluorosis.
|
From page 48... ...
If recommended fluoride concentrations in drinking water should still be expressed in a range related to mean temperature, the MCL might also be expressed more logically as a temperature-related range rather than a single figure. Overall, the evidence of the current current relation of dental fluorosis to fluoride in drinking water in the United States is still sparse, and the evidence that does exist is too inconsistent to be used as a basis for recommending changes in EPA regulations.
|
From page 49... ...
Studies should be conducted on the relation between water fluoride concentrations and dental fluorosis in various climatic zones. Findings could serve as a basis for any needed revision of the 1962 PHS guidelines.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.