Uptake of fluoride by sound and artificially carious enamel in vitro following application of topical sodium and amine fluorides.

The aim of this investigation was to compare fluoride uptake and retention by sound and artificially carious enamel, after the topical application of a neutral sodium fluoride solution (NaF) or a commercial preparation containing aqueous amine fluorides (AF) 297 and 335 (Elmex Fluid, GABA International, Basel, Switzerland). Ten pairs of extracted premolars were used, one of each pair being treated with NaF and the other with AF. A lactic acid gel technique was used to produce artificial caries lesions on one-half of the buccal surface of the premolar crowns. Estimates at selected depths of pretreatment fluoride concentration, uptake and retention were made using a step-wise acid-etch sampling technique. AF produced much greater uptake than NaF, the difference being most marked in the deeper layers of the artificial lesions, suggesting that the amine fluorides had a strong affinity for demineralized enamel. After storage in normal saline for 1 week during which partial loss of the acquired fluoride occurred, the percentages retained ranged from 37 (NaF) to 65 percent (AF). It was concluded that AF enhanced both uptake and retention of fluoride by (artificial) early enamel caries lesions.