Enamel fluoride uptake from a new APF foam.

Abstract

There is concern that the ingestion of fluoride (F) from topical application of 1.23% APF gel may cause gastric irritation and other side effects. In this in vitro study, a newly developed APF-based foam was tested. Sound human enamel was treated for 4 rain with APF foam or a conventional APF gel (Nupro®), both containing 1.23 % F. Enamel biopsies were obtained using the acid-etch technique. There was a significant increase (P < 0.001) in F uptake from the two F agents compared with their untreated controls. The uptake of F from the new foam and Nupro gel in the outer 15 ~tm enamel were 1736 and 2596 ppm, respectively. The difference in F uptake from the foam and gel preparations at 5 ~tm depth was not statistically significant (P = 0.074). Clinically, the amount foam needed for full-mouth treatment is less than I g, whereas for APF gel it is nearly 4 g. The topical application of acidulated phosphate fluoride (APF) gels has been demonstrated by clinical studies to reduce dental caries to an average of 25% (Clarkson and Wei 1982; Mellberg and Ripa 1983). The Accepted Dental Therapeutics (1984) listed 22 APF gels accepted by the American Dental Association (ADA). Most of these gels contain 1.23% F (as NaF and HF), phosphoric acid and carboxymethyl cellulose as the gelling base. The pH is usually between 3.0 and 4.5 and the viscosity of 7000 to 20,000 centipoises. Fluoride gels have the advantage of being used in trays, enabling the entire mouth to be treated in a single application. Because the F gels are viscous, the use of a well-fitting tray is essential to facilitate the flow of the gel into the interproximal surfaces of teeth. Concern has been expressed recently about the potential risk of excessive F ingestion following application of 1.23% APF gels. Ekstrand et al. (1981) reported that an average of 78% (31.2 mg F) of topically applied 1.23% APF gels was ingested when vacuum-molded trays were used on children 5-16 years of age. LeCompte and Whitford (1981) reported that the average amount of F retained by children approached 14 mg or 54% of the applied dose using the cotton-roll isolation technique. However, the amount of F ingested was greatly reduced when suction was applied and when better fitting trays were used (LeCompte and Doyle 1985). The ingested from APF gels may cause side-effects such as nausea, vomiting, and gastrointestinal pain. Recently, in vitro evidence indicated that there is no direct relationship between the F content of APF gels and their ability to reduce enamel solubility, (Shannon and Edmonds 1978; Hattab 1984), increase enamel uptake, (Dijkman et al. 1982; Naleway 1985), and decrease the carious lesion depth (Sluiter and PurdellLewis 1984). Based on these findings and the concern for the potential risk of overdosage, suggestions have been made to lower the F concentration in gels and/or to use a well controlled application technique. In an attempt to minimize the risk of F overdosage and to maintain the efficacy of topical F treatment, a new foam-based APF agent has been developed. The aim of the present study was to determine whether a foam-based APF agent is effective in producing enamel F uptake to concentrations attained by conventional APF gels. Because the foam is considerably lighter than gels, it will fill a topical application tray with a much smaller weight of the agent and hence the total amount of F ingested could potentially be less. This will be the subject of a subsequent study.