Effectiveness of two fluoridation measures on erosion progression in human enamel and dentine in vitro

The aim of the present study was to evaluate the effect of fluoride on the progression of erosive demineralisation in human enamel and dentine using a cyclic de- and remineralisation model in vitro. The mineral content expressed in micrometres was determined daily by longitudinal microradiography (LMR) and presented as cumulative mineral loss over 5 days. For erosive demineralisation, all samples were immersed in 0.05 M citric acid (pH 2.3) for 6x10 min/day and stored in a remineralisation solution. Fluoridation measures were performed as follows: group 1: control, no fluoridation; group 2: toothpaste fluoridation 3x5 min/daily (NaF, 0.15% F-); group 3: toothpaste fluoridation as group 2 and additionally application of a fluoride mouthrinse (Olaflur/SnF2, 0.025%F-) 3x5 min/daily and on days 1 and 3 gel fluoridation (Olaflur/NaF; 1.25% F-) for 1x5 min. After the first experimental day, no significant differences were found between the groups. However, after 5 days the erosive mineral loss values for enamel were 147.5+/-18.7 microm in the control group, 128.1+/-15.0 microm in group 2 (p< or =0.05) and 116.1+/-12.4 microm in group 3 (p< or =0.001). In dentine, the respective values were 136.7+/-16.4, 111.8+/-26.9 (p< or =0.001) and 60.3+/-17.8 (p< or =0.001). The intensive fluoridation significantly reduced erosion progression in enamel but had a more pronounced effect on dentine. The results suggest that subjects with erosive lesions should use an intensive fluoridation measure.