Dental caries is a bacterial disease that begins with demineralization of the outermost dental enamel and progresses, if not halted, to loss of tooth substance and infection of the dental pulp. Demineralization begins with acid formation in dental plaque, the acid being a by-product of the metabolism of simple carbohydrates (sugars, cooked starches) by certain plaque-resident bacteria, principally the mutans streptococci. If demineralization is not checked, it leads to tissue loss and further bacterial penetration. The carious process is reversible in the early demineralization stage: Fluoride and other minerals in plaque can buffer the acid and lead to remineralization of the early lesion. Prevention of dental caries, therefore, is based on promoting an intra-oral environment in which demineralized enamel can quickly be remineralized, and where plaque pH does not remain below neutral for prolonged periods.
According to the United States Department of Agriculture, average sugar consumption in the United States rose from 122 pounds per person in 1981 to 154 pounds per person in 1997, one of the highest levels of sugar consumption in the world. Reasonable restriction of simple-carbohydrate foods (candies, sugared soft drinks, cookies) is prudent for caries-susceptible persons, despite the paucity of population-based data to demonstrate the effectiveness of such action. Dental sealants, applied
Fluoride acts in several ways to prevent caries. The principle action is thought to be that fluoride in dental plaque inhibits the initial demineralization of enamel, and then promotes remineralization of early lesions. The constant availability of fluoride in plaque to respond to acid challenges leads to the gradual establishment of a more acid-resistant enamel crystal as a result of the repeated cycles of demineralization and remineralization. Fluoride also inhibits glycolysis, the process by which cariogenic bacteria metabolize simple carbohydrates, and there is evidence that fluoride also has antibacterial action in plaque. There may be some incorporation of fluoride into the enamel crystal prior to tooth eruption, which may increase resistance to solubility in acids.
Fluoride in toothpaste is considered by many researchers to be the most effective use of fluoride in controlling caries, although today fluoride is available from a variety of sources. Brushing with a fluoride toothpaste twice each day, a social norm in American society, ensures that fluoride will be present in dental plaque when an acid challenge arises. Addition of fluoride to public water supplies at around 1.0 parts per million has particular benefits for lower socioeconomic groups who may not brush their teeth that often. Fluoride is also used effectively in school-based programs as a mouthrinse or as fluoride supplements, and dentists can apply fluoride gels or varnishes directly to the teeth of their more caries-susceptible patients. Use of fluoride in all these ways is considered to be the chief reason for the remarkable improvement in the oral health of Americans between 1980 and 1995.
BRIAN A. BURT
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