The effect of varying concentrations of fluoridated milk on enamel remineralisation in vitro.

The aim of this in vitro single blind study was to investigate the dose response of fluoride in milk on enamel demineralisation and remineralisation under pH cycling using transverse microradiography (TMR). Enamel slabs (n = 11) with caries-like lesions were exposed to milk containing 6 different fluoride concentrations (0, 0.25, 0.5, 1.0, 5.0 and 10.0 ppm F). On each of the 14 days of the cycling period the lesions were exposed to five 2-minute periods of cariogenic challenge (1.5 mM CaCl2, 0.9 mM KH2PO4 and 50 mM acetic acid at pH 5.0) and two 5-min periods in milk plus 10 min in a milk/saliva (1:3) slurry. The slabs were stored at 37°C in artificial saliva throughout the cycling period and demineralisation and remineralisation was assessed by TMR using dedicated image software. Remineralisation (ΔZ) was observed in all fluoride groups in contrast to demineralisation in the non-fluoride control. Remineralisation was significant (p < 0.05) for all concentrations above 1.0 ppm F. The results showed that fluoride concentration in milk exhibited a clear dose dependency and that the presence of fluoride even at low concentrations promoted remineralisation in this pH-cycling model.