Our aim was to investigate the effect of TiF4 solutions on mineral loss on enamel and dentine in vitro. Samples were fluoridated 1 x 5 min per day with 1.64% w/v TiF4 or 2.2% w/v NaF solutions, each with a pH of 1.2, and then subjected to a cyclic de- and remineralization procedure for 5 days. Demineralization was performed for 6 x 10 min per day with citric acid ( pH 2.3). In controls no fluoridation was performed. Mineral content was determined by longitudinal microradiography. Enamel mineral loss was markedly reduced by both fluoride solutions, but TiF4 was significantly more effective than NaF: cumulative mineral loss on day 3 was 61.7 +/- 15.0 mu m in the NaF and 34.2 +/- 13.1 mu m in the TiF4 group (p <= 0.001) compared with 121.0 +/- 27.0 mu m in the control group. Dentine mineral loss ceased after both TiF4 and NaF applications ( cumulative mineral loss on day 5 in controls: 61.0 +/- 17.0 mu m, in the TiF4 group: 15.4 +/- 13.4 mu m and in the NaF group: 21.8 +/- 11.8 mu m). Both TiF4 and NaF application reduced mineral loss both on enamel and dentine, which could open new possibilities for a symptomatic therapy of erosions. Copyright (c) 2007 S. Karger AG, Basel.