Fluoride is unable to reduce dental erosion from soft drinks

The main aim of the present study was to compare the erosive capabilities of some fruit-flavoured drinks, fresh or saturated with CaF2, with their content of acids and with previous results from some carbonated soft drinks. The other aim was to measure and compare the rates of dissolution of CaF2 in some carbonated and non-carbonated drinks and water. Seven commercially available fruit-flavoured drinks were diluted for drinking. Two human molars, each with two approximately 4 x 4 mm windows, were exposed continuously to 500 ml of each drink with or without prior equilibration with CaF2 under gentle agitation for 48 h. The depths of the erosions were then measured on microradiographs made from sections. Dissolution rate of CaF2 was measured by suspending 0.5 g of the salt in 0.5 litre of the drinks for 2, 10 and 60 min followed by solution analysis. The pH of the drinks was 2.83-3.51. The amount of NaOH required to bring pH to 5.5 ranged from 12-42 mmol/l, which is more than the amount necessary for most carbonated soft drinks. Equilibration with CaF2 gave total fluoride concentrations of 3-8 ppm. The depths of the lesions induced by the drinks without added fluoride were 450-625 microm whilst those developed by the drinks equilibrated with CaF2 were 350-625 microm. The dissolution of CaF2 was faster in the carbonated drinks and in distilled water than in the non-carbonated drinks. In conclusion, non-carbonated fruit-flavoured drinks contain considerable amounts of acids which, in vitro, induce erosions in teeth similar to those induced by carbonated soft drinks. Saturation with CaF2 reduced the in vitro development of erosions by 28% induced by drinks with pH above 3; in drinks with pH below 3, erosions were not affected by pH, despite total fluoride concentrations of up to 20 ppm.