Evaluation of Topical Fluoride Preparations

Abstract

For practical reasons, evaluation of topical fluoride products must depend upon clinical and laboratory assessments. While not always a good predictor of clinical efficacy by itself, fluoride uptake is the most commonly used laboratory test. A consideration of the relationship between possible anticaries mechanisms of fluoride, different product types, and the meaning of various kinds of fluoride uptake data suggests that both the amount of fluoride taken up by early lesions and the amount of ambient fluoride present at a cariogenic site may play key roles in determining the efficacy of a product. While formulations applied annually or semi-annually probably depend on fluoride deposition, those used daily might not. There are no clear data supporting the superiority of one fluoride compound over another, even for infrequently used products, although there are significant differences among them in fluoride uptake by enamel. This suggests that fluoride uptake in vivo at a cariogenic site might actually be different from that suggested by in vitro data, or that larger differences are required for a clinical effect to be observable. Clinical data support the conclusion that a large increase in the fluoride concentration of a product will somewhat increase its Anticaries effectiveness, although the increase will not be linearly related to concentration. There also are no obvious differences in clinical effectiveness caused by the addition of gelling agents to topical solutions. Fluoride varnishes are clinically effective but have not been shown to be superior to topical solutions or gels. The abrasive, humectant, and thickener systems used in most prophylaxis pastes reduce both fluoride uptake and clinical effectiveness, even though, in some cases, the components may be chemically compatible. Precleaning prior to a topical application appears unnecessary, but a delay in rinsing after the application and longer application times appear beneficial. Mouthrinse formulations essentially differ only in fluoride source, concentration, and pH. Higher fluoride concentrations are likely to provide greater benefits, but pH differences probably will not. The stannous ion in SnF2 rinses is unstable, and its effect on anticaries activity is unknown. This review of the composition of topical fluoride products emphasizes the lack of clear evidence for the making of definite scientific judgments regarding relative clinical efficacy. Future efforts should be directed toward the development of test models that utilize the natural oral environment, so that more precise and valid comparison of compositions may be made.