Methods: Eight teeth were treated with one of the following F-releasing agents: Group 1 (4 teeth): Dentsply All Solutions 2 %neutral sodium fluoride solution applied for 1 minute, Group 2 (4 teeth): Dentsply All Solutions neutral sodium fluoride rinse applied for 4 minutes. The teeth were submerged and agitated in the rinse for 1 or 4 minutes. After topical application, the teeth were dried in high-vacuum chamber for 48 hours, then sectioned into two halves and dry-polished with 240, 320, 400 and 600 grit SiC papers and 10,1 and 0.1 µm grit alumina-coated films. F penetration was evaluated continuously at 5 µm intervals (up to 25 µm) starting from the top of the cross-section of tooth-enamel using an electron probe x-ray micro-analyzer (EPMA) (JEOL JXA-733 Superprobe) by wavelength dispersive spectrometry. The statistical analysis used was a t-test at (P<0.05 significance level).
Results: The following values in F wt% (± SD)) were observed: 1-minute exposure 0.21 (0.04) at 5 µm, 0.20 (0.02) at 10 µm, 0.15 (0.02) at 15 µm, 0.13 (0.01) at 20 µm, and 0.12 (0.004) at 25 µm. The 4-minute exposure showed 0.38 (0.19) at 5 µm, 0.41 (0.18) at 10 µm, 0.39 (0.14) at 15 µm, 0.33 (0.07) at 20 µm, and 0.24 (0.06) at 25 µm. The results were not statistically significantly different between the enamel fluoride incorporation after 1 or 4 minute application of the 2% neutral fluoride solution at any of the depth measurements made.
Conclusions: The use of the neutral fluoride solution for 1 minute or 4 minutes had no significant difference in fluoride incorporation into the enamel.