Demineralization and remineralization around orthodontic appliances: an in vivo study.

Background Topical fluoride therapy (TFT) in the form of varnish, gel, mouthrinse or toothpaste has been used extensively as a caries-preventive intervention for over three decades. Objectives To determine the effectiveness and safety of fluoride varnishes, gels, mouthrinses, and toothpastes in the prevention of dental caries in children and to examine factors potentially modifying their effect. Search strategy We searched the Cochrane Oral Health Group's Trials Register (May 2000), CENTRAL (The Cochrane Library Issue 2, 2000), MEDLINE (1966 to January 2000), plus several other databases. We handsearched journals, reference lists of articles and contacted selected authors and manufacturers. Selection criteria Randomized or quasi-randomized controlled trials with blind outcome assessment, comparing fluoride varnish, gel, mouthrinse, or toothpaste with placebo or no treatment in children up to 16 years during at least 1 year. The main outcome was caries increment measured by the change in decayed, missing and filled tooth surfaces (D(M)FS). Data collection and analysis Inclusion decisions, quality assessment and data extraction were duplicated in a random sample of one third of studies, and consensus achieved by discussion or a third party. Authors were contacted for missing data. The primary measure of effect was the prevented fraction (PF) that is the difference in mean caries increments between the treatment and control groups expressed as a percentage of the mean increment in the control group. Random effects meta-analyses were performed where data could be pooled. Potential sources of heterogeneity were examined in random effects metaregression analyses. Main results There were 144 studies included. For the 133 that contributed data for meta-analysis (involving 65,169 children) the D(M)FS pooled prevented fraction estimate was 26% (95% CI, 24% to 29%; p Reviewer's conclusions The benefits of topical fluorides have been firmly established on a sizeable body of evidence from randomized controlled trials. While the formal examination of sources of heterogeneity between studies has been important in the overall conclusions reached, these should be interpreted with caution. We were unable to reach definite conclusions about any adverse effects that might result from the use of topical fluorides, because data reported in the trials are scarce.

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Topical fluoride (toothpastes, mouthrinses, gels or varnishes) for preventing dental caries in children and adolescents

For many years after the discovery of its caries preventive effect, fluoride was thought to be primarily active by lowering the solubility of the apatitic mineral phase of the dental hard tissues. Recent findings have shed new light on the mechanisms by which fluoride inhibits or delays dental caries. Fluoride present in the oral fluids alters the rate of the naturally occurring dissolution and reprecipitation processes at the tooth-oral fluid interface. Demineralization of enamel is inhibited by concentrations of fluoride in the sub-ppm range. Likewise, remineralization of incipient caries lesions (the earliest stage of enamel caries) is accelerated by trace amounts of fluoride. As these two processes comprise dental caries the physiological balance between hard tissue breakdown and repair is favorably shifted by fluoride. The driving force for both phenomena is thermodynamic, that is, fluorapatite or a fluoridated hydroxyapatite may form when fluoride is supplied at low concentrations. This article critically reviews the current information about tooth-fluoride interactions, both from laboratory and clinical studies.

Mechanistic Aspects of the Interactions Between Fluoride and Dental Enamel

The aim of this review has been to suggest that future fluoride preventive programs should be based on what is at present known about the possible cariostatic mechanisms of fluoride. The relative role of enamel fluoride in caries prevention has become increasingly questioned during the last two decades. No significant relationship has been demonstrated between caries experience of the individual and fluoride content of the enamel. Furthermore, the fluoride content in surface enamel between teeth developed in low and "optimal" fluoride areas is too small to explain any significant effect on dissolution rate of the enamel. As the major explanation for the cariostatic effect of fluoride must therefore be sought in its local effect on the oral environment, the possible effects on plaque colonization, composition and metabolic activities are discussed. The effect of even low concentrations of fluoride in the liquid phase on enamel dissolution is described, and it is concluded that the major cariostatic effect of water fluoridation, fluoride tooth paste and mouth rinses can probably be ascribed to regular increases in fluoride ion activity in the oral fluids. The effect of high concentrations of topical fluoride solutions is thought to be a result of a slow dissolution of calcium fluoride deposited in initial caries lesions, whereby an increased fluoride ion concentration is maintained locally for longer periods of time. Finally, the clinical consequences of these considerations are described.

Rational use of fluorides in caries prevention. A concept based on possible cariostatic mechanisms.

The recent literature extensively describes the role of ambient fluoride in the de- and remineralization of dental enamel. Fluoride in sub-ppm concentrations is effective in promoting mineral deposition and inhibiting mineral dissolution. The latter phenomenon is most likely attributable to the concomitant precipitation of a fluoride-rich mineral phase which inhibits further dissolution. These fundamental processes result in an inhibition of enamel demineralization and an enhancement of enamel lesion remineralization. Alternatively, fluoride may also induce the 'arrestment' of enamel lesions. For the in vivo patterns and the effects of caries-preventive substances to be studied, de- and remineralization can best be examined with a pH-cycling system in which the pH depressions occurring in the oral environment are mimicked in a laboratory model. Such an approach has proved useful in developing optimal fluoride schemes which can be tested in animal, intraoral, and clinical studies.

In vitro studies on the effects of fluoride on de- and remineralization.

DMFT and DMFS differences between treated and untreated groups remained statistically significant after 23 months. Residual fluoride concentrations were found in enamel layers of exfoliated deciduous teeth collected from the treated group six to nine months after the treatments.

Residual anticaries effect of repeated topical sodium fluoride applications by mouthpieces

Osborne-Mendel rats 22–25 days of age were subjected to a 7-day precaries test period during which they were fed a high starch diet and drank distilled water containing no added fluoride or with 10, 5

Caries inhibition in the rat by water-borne and enamel-bound fluoride.

Repeated topical applications of 1.1% sodium fluoride in water-soluble gels apparently reduced the already low caries rate in children who have lived in Charlotte, NC, all their lives. The community water supply was fluoridated in 1949. After about two years, the concentration of fluoride in permanent tooth enamel of treated children was nearly 3,000 ppm as compared to 1,700 ppm in untreated children.

https://jada.ada.org/article/S0002-8177(71)22022-5/pdf

Incremental Rates of Dental Caries after Repeated Topical Sodium Fluoride Applications in Children with Lifelong Consumption of Fluoridated Water

Fluoride acquisition by deciduous enamel of 11- to 14-year-old children, living in a fluoridated area, was studied during repeated topical applications of acidulated phosphate fluoride gel drops in plastic mouthpieces. Enamel fluoride progressively increased as the number of treatments increased, reaching a concentration of 1,785 ppm at a depth of 5μ after an average of 56 treatments.

J.R. Mellberg

Papers

Residual anticaries effect of repeated topical sodium fluoride applications by mouthpieces

Caries inhibition in the rat by water-borne and enamel-bound fluoride.

Incremental Rates of Dental Caries after Repeated Topical Sodium Fluoride Applications in Children with Lifelong Consumption of Fluoridated Water

Acquisition of Fluoride in Vivo by Enamel from Repeated Topical Sodium Fluoride Applications in a Fluoridated Area: A Preliminary Report

Acquisition of fluoride in vivo by deciduous enamel from daily topical sodium fluoride applications over 21 months.