The effect on dental enamel of the frequency of consumption of fluoridated milk with a cariogenic challenge in situ.

OBJECTIVES: To evaluate the effect on enamel of varying the frequency of consumption of 1.0 mg F in milk once per day, twice per day or once every other day under cariogenic challenge in situ. MATERIALS AND METHODS: In a controlled, randomised, cross-over, single-blind study, 25 subjects wore an intra-oral lower removable appliance with enamel slabs for 21 days during each study arm. Subjects used F-free toothpaste, the cariogenic challenge comprising of five 2 min dippings per day in a 12% sucrose solution. Subjects dipped the appliances in 50 ml of 5.0 ppm fluoridated milk for five minutes during the test period once per day, twice per day, and once every other day and drank 200 ml of the same milk, once per day, twice per day (100 ml each time), or once every other day (200 ml) immediately on re-inserting their appliance in order to replicate topical and systemic effects. Slabs were analysed with surface microhardness (SMH) for protection against further demineralisation and transverse microradiography (TMR) to assess changes in mineralisation. RESULTS: Using SMH, 200 ml of 5.0 ppm F milk once per day was significantly better than 100 ml of 5.0 ppm F twice/day (p < 0.05) and 200 ml once every other day, but not significantly. Using TMR there was a statistically significant difference in mineral loss of enamel between baseline and treatment for all groups, but not between groups. CONCLUSIONS: Drinking 200 ml of 5.0 ppm milk once per day every day protected enamel against further demineralisation whereas all three frequencies were effective in promoting remineralisation.