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Fluoride

8. What are the beneficial effects of fluoride on teeth?

  • 8.1 Does fluoride protect teeth from cavities?
  • 8.2 What fluoridated products have been used to prevent cavities?

The source document for this Digest states:

It has been recognized for over five decades that fluoride may have both beneficial and potentially harmful effects on dental health. While the prevalence of dental caries is inversely related to a range of concentrations of fluoride in drinking-water consumed, the prevalence of dental fluorosis has been shown to be positively related to fluoride intake from many sources (Fejerskov et al., 1988, 1996). Public health programmes seeking to maximize the beneficial effects of fluoride on dental health through the introduction of fluoridated drinking-water have, at the same time, strived to minimize its adverse fluorotic effects on teeth. Based upon the studies conducted by Dean and colleagues five decades ago, the "optimum" level of fluoride in drinking-water, associated with the maximum level of dental caries protection and minimum level of dental fluorosis, was considered to be approximately 1 mg/litre. The effects of fluoride on dental health were examined by a WHO Expert Committee (WHO, 1994).

Source & ©: IPCS "Environmental Health Criteria for Fluorides", (EHC 227),
Chapter 8: Effects on humans, section 8.1.3.8: Dental effects
 

8.1 Does fluoride protect teeth from cavities?

The source document for this Digest states:

Dental caries

Since the first reports by Dean and colleagues published in the 1930s, oral fluoride is still considered an effective means of reducing dental caries. Historically, populations consuming fluoridated drinking-water had a much lower prevalence of dental caries than did those consuming non-fluoridated drinking-water. Over time, the difference in caries prevalence among those consuming fluoridated and non-fluoridated drinking-water has narrowed significantly. This apparent diminution in the cariostatic effectiveness of fluoridated drinking-water is likely attributable to a "diffusion" in which individuals consuming non-fluoridated drinking-water may consume significant amounts of beverages prepared in other locales with fluoridated drinking-water, as well as exposure to fluoride through the use of dental care products — mainly fluoridated toothpaste. It has been estimated that whereas approximately 210 million individuals throughout the world consume drinking-water containing levels of fluoride considered adequate for the prevention of dental caries, approximately 500 million people use fluoridated toothpastes (WHO, 1994).

Historically, it was believed that fluoride needed to become incorporated into the crystal lattice of enamel in order to effectively prevent the development of dental caries. Fluoride was considered to improve lattice stability and render the enamel less soluble to acid demineralization. Since the incorporation of fluoride into enamel, as partially fluoridated hydroxyapatite, was believed to be essential for its action, fluoride was thought best ingested. There is now, however, an increasing body of evidence to suggest that a substantial part of the cariostatic activity of fluoride is due to its effects on erupted teeth, and that the continual presence of fluoride in the saliva and in the fluid phase of dental plaque is critical to its mechanism of action. There is a growing consensus that through its interaction with the surface of enamel, fluoride in saliva and dental plaque inhibits the demineralization and promotes the remineralization taking place at the surface of the tooth.

Source & ©: IPCS "Environmental Health Criteria for Fluorides", (EHC 227),
Chapter 8: Effects on humans, section 8.1.3.8: Dental effects
 

8.2 What fluoridated products have been used to prevent cavities?

The source document for this Digest states:

Since the introduction of controlled fluoridated drinking-water, efforts to reduce dental caries have been extended to include the use of fluoridated toothpaste, mouth rinses and topically applied dental treatments (e.g., gels, varnishes, solutions), as well as through the use of fluoride supplements, fluoridated milk and fluoridated salt. The effectiveness and factors affecting the implementation of these various exposure regimens have been reviewed in detail by WHO (1994), and therefore only a brief summary is presented here.

The controlled fluoridation of community drinking-water to an optimum level is one of the most cost-effective means of delivering fluoride to large numbers of individuals. This method of fluoride delivery requires a suitable community-wide drinking-water delivery system along with a reasonable level of technological development (e.g., infrastructure, equipment and appropriately trained support personnel). Depending upon the annual average maximum daily air temperature, recommended levels of fluoride in drinking-water considered useful for the prevention of dental caries have ranged from 0.5 to 1.2 mg/litre.

Some countries have introduced controlled fluoridated salt as a means of reducing the prevalence of dental caries among their respective populations. Unlike controlled fluoridated drinking-water and toothpastes, there is little quantitative information on the cariostatic action of fluoridated salt, although it is considered to act in a manner like that of fluoridated drinking-water. The optimum concentration of fluoride in salt needed to reduce the incidence of dental caries must take into account the level of salt intake and the concentration of fluoride in drinking-water in individual geographical areas; however, 200 mg fluoride/kg salt has been suggested to be a minimum value (WHO, 1994).

Formerly, the administration of fluoridated milk to children was considered to be a suitable means of increasing their intake of fluoride; however, little quantitative information is available on the efficacy of this delivery system in the prevention of dental caries. To be effective as a means of delivering fluoride to children, implementation of a fluoridated milk programme requires close cooperation with the dairy industry as well as a widespread system of distribution.

It has been estimated that, worldwide, almost twice as many people are exposed to fluoride for the prevention of dental caries through the use of toothpastes as from the consumption of controlled fluoridated drinking-water. In many countries, fluoridated toothpastes, which usually contain approximately 1000 mg fluoride/kg, represent more than 95% of total dentifrice sold.

The use of these products is considered to be one of the major factors responsible for the gradual decline in the prevalence of dental caries in most industrialized countries. In areas where the prevention of dental caries through the widespread use of fluoridated drinking-water, salt or milk may not be feasible, the use of fluoridated toothpastes remains an effective means of improving dental health.

Fluoride supplements, in the form of tablets, liquid drops or lozenges, are intended to provide a systemic source of fluoride when fluoridated drinking-water is not available. Problems associated with the widespread use of such supplements include poor compliance among socially and economically disadvantaged groups and the potentially inappropriate use of these products by those already consuming drinking-water containing optimal amounts of fluoride. Moreover, the results of studies suggest that fluoride is most effective when continually present at low levels in saliva and plaque fluid. In a number of jurisdictions, the recommended daily dosage of fluoride supplements is linked to the level of fluoride in the drinking-water as well as the age of the child. Although fluoride supplements may be appropriate for use in certain areas where the prevalence of dental caries is high, available data on the efficacy of this fluoride delivery system in preventing dental caries are equivocal, and there appears to be a growing consensus that fluoride supplements have a limited public health role in improving dental health.

The use of fluoridated mouth rinses has achieved a significant level of popularity among publicly based health care programmes, particularly those involving school-aged children. The levels of fluoride in these mouth rinses (0.05 or 0.2%) are related to whether they are recommended for daily or weekly use. The efficacy of fluoridated mouth rinses in the prevention of dental caries is related to the frequency of use, the level of compliance and exposure to other sources of fluoride, most notably in drinking-water. The use of fluoridated mouth rinses may be recommended for individuals with an elevated risk of dental caries, although the mouth rinses may not be appropriate for use by children younger than 6 years of age, due to their propensity to swallow significant amounts of such material, thereby increasing their risk of developing dental fluorosis.

Solutions, gels or varnishes usually applied infrequently over the course of a year by dental care professionals may be most efficacious in individuals with an elevated risk of dental caries. Owing to the level of fluoride in these materials (e.g., up to 22 300 mg/kg), health care professionals must follow protocols that reduce inadvertent ingestion of significant amounts of these products by younger children, which could cause acute toxic effects.

Source & ©: IPCS "Environmental Health Criteria for Fluorides", (EHC 227),
Chapter 8: Effects on humans, section 8.1.3.8: Dental effects
 


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