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Saturday, November 19, 2011

Fluorides in Dentistry and Its role in preventing Caries

Dental caries is a major dental disease affecting a large population of the world. It impairs the quality of life of any people causing pain and discomfort. It's very high morbidity potential has brought this disease into the main focus of the dental health professionals.

The cariostatic efiicacy of the fluorides has been convincingly demonstrated and the recent decline in caries prevalence is primarily attributed to the increase use of various fluoride agents.

The Federal Register of United States Food and Drug Administration describes fluoride as an essential element. The WHO Expert Committee on Trace elements has included fluorine as one among the 14 physiollogically essential elements for normal growth and development.

Fluorine is a member of halogen family with atomic number 9 and atomic weight 19, It is a highly reactive electro negative element and will not occur in free form. It occurs in form of fluorides or molecular state. It is 17th in order of frequency of occurrence of the elements, representing about 0.06% to 0.09% of earth's crust. Fluorine occurs in combined form in wide variety of minerals, such as Fluorspar, Fluorapatitle etc. Fluoride ions have strong tendency to form complexes with heavy metals in aqueous solutions.

Since the availability of fluorides vary from country to country, a total intake of 0.05 to 0.07mg of fluoride per kilogram body weight has been found to be optimum intake for human beings.The average daily intake of fluoride by adults from dry food substances range from 0.2 to 1.8mg and daily average intake from water containing 1ppm fluoride is about 1.5mg. The total fluid intake in children between 1-12 years age ranges from 700-1300ml/day, which at a level of1ppm fluoride would result in an ingestion of about 0.7mg/day for the younger, bottle fed children, to about 1.3mg fluoride/day for 12 year old group.

 The benefits of fluoride in the reduction of dental caries have been known for years, but its exact mechanism of action is not completely understood. The resistance may increase from both systemic and topical application of fluorides. The assumed mechanisms by which fluorides helpin preventing caries are;

1) Increased enamel resistance/Reduction in enamel Solubility:
  It has been well established that dental caries involves in dissolution of enamel by acids from bacterial plaque and that dissolution id inhibited by fluorides. Because fluorapatite is formed which is a less soluble mineral, it has been thought that the anticaries effect of fluoride is the result of reduced solubility. The dissolution of enamel during caries attack is a complicated process. When the enamel is exposed to a pH of 5.5 or lower, it will dissolve. This ordinarily occurs beneath a bacterial plaque. The concentrations of calcium and phosphate increase in the solution. When the plaque stops producing acids, the pH rises and the dissolved minerals get precipitated. Thus, carious dissolution is a cyclical process consisting of demineralization and reprecipitation.
The presence of fluorides reduces the solubility of enamel by promoting the precipitation of hydroxyapatite and phosphate mineral. When hydroxyapatite is exposed to low fluoride concentrations a layer of fluorapatite is formed on hydroxyapatite crystals. This layer is more acid stable and is not dissolved quickly.

The greatest importance of the fluoride to the maturation process lies in its ability to increase the rate of mineralization of hypomineralized areas. Newly erupted teeth often have hypomineralized areas that are prone to dental caries. Fluorides increase the rate of mineralization, or post eruptive maturation of these areas. Organic material is also deposited into the enamel surface to further increase its resistance to dental caries.

Fluoride also plays a critical role in reducing dental caries by enhancing remineralization. Remineralization, the deposition of minerals into previously damaged areas of the tooth is a dynamic process that results in reduced enamel solubility. This increase in enamel resistance is achieved through the growth of crystals which become larger and are more resistant to caries attack.
The most effective remineralizing solution contains fluorine in combination with calcium and phosphate ions, these calcium and phosphate ions come from two sources: the saliva and tooth mineral dissolved during demineralization.Fluorine enhances the remineralization process by accelerating the growth of enamel crystals that have demineralized.
The composition of remineralized enamel is different from that of normal enamel. Fluoride enhances the rate of remineralization from calcium phosphate solutions. Remineralization of white spots is increased two fold. However large amounts of fluoride in calcium phosphate solutions may actually inhibit remineralization,by formation of calcium fluoride which prevents hydroxyapatite crystal growth.

 Fluoride forms a layer on the surface of the enamel which is more resistant to acid dissolution and helps in further extension of caries. It contains higher mineral content with large crystal structure and not easily caries prone.

Fluorides inhibit bacterial enzymatic activity involved in carbohydrate metabolism. Fluoride interferes with oral bacteria in two ways. In higher concentrations it is bactericidal(kills bacteria). In lower concentrations it is bacteriostatic( inhibits the multiplication of bacteria). Fluoride lodges in plaque and inhibits bacterial enzymes responsible for acid metabolism.

Fluoride interacts with the bacterial cell rapidly and in a pH dependent fashion. The tightly bound fraction is saturated at low fluoride concentration by a rapid process that is independent of energy, temperature and the presence of inhibitors. This phenomena occurs with both fluorine sensitive and fluorine resistant strains of oral bacteria and under both aerobic and anaerobic conditions.

Fluoride in normal concentrations is far more helpful in preventing caries and fighting tooth decay. Apart from the above mentioned actions fluoride also helps in modification of tooth morphology when ingested during tooth development, there is evidence of formation of more caries resistant tooth slightly smaller with shallow fissures.


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