Potential of 4 per cent silver fluoride to induce fluorosis in rats: clinical implications

The Health Department in Western Australia uses a 40 per cent silver fluoride (AgF) solution for prevention and treatment of dental caries in children. Analysis of this solution has revealed high fluoride concentrations (75,000-120,000 mg/L), raising concerns of potential toxicity and prompting investigation of clinical protocols utilizing low-strength AgF in an animal model. A single topical application of 4 per cent AgF solution to Sprague-Dawley rats resulted in moderate to severe localized fluorosis in 24 per cent of animals. In a second experiment, caries was induced in rats aged 19 days; six weeks later, between one-four carious molar teeth from each rat were treated with 4 per cent AgF (atraumatic technique). A generalized form of fluorosis developed in the continually growing incisors of less than 10 per cent of animals which had one or two carious teeth treated, and in 70-90 per cent of rats which received AgF to either three or four carious teeth. These results confirm the potential of a 4 per cent AgF solution to induce fluorosis and support previous recommendations that AgF at its empirical concentration of 40 per cent should be withdrawn from clinical use.