In Vitro Evaluation of Different Fluoride Toothpastes on Enamel Remineralization

Objectives: The purpose of this in vitro study was to evaluate the effect of four children's toothpastes containing sodium fluoride in different concentrations on enamel demineralization and remineralization compared to a conventional fluoride (F) toothpaste using a pH cycling model.
Methods: During an eight day pH-cycling protocol, 60 bovine enamel slabs were immersed twice daily, after 4h demineralization and 20h remineralization periods, for 1 min, in the following toothpaste slurries: 1- F-free (negative control); 2 - 500 ppm; 3 - 750 ppm; 4 - 1100 ppm; 5 - 1450 ppm; and 6 - 1.100 ppm conventional F toothpaste (positive control). Surface microhardness (SMH) was assessed initially (SMHi) and after the experimental period (SMHf). Percentage change of SMH (%SMHC) was determined and a scanning electron microscope (SEM) and 3-D profilometric analysis were performed in 3 samples of each group after the experiment. Statistical analysis was performed using SPSS 20.0 (IBM, New York, NY, USA) software. The mean and standard deviation of each group were calculated and the statistical differences were identified among the groups by Kruskall-Wallis test ( P < 0.05) and Dunn and Mann-Whitney tests were used to compare the significant differences (P < 0.05) between the groups.
Results: Only F-free children's toothpaste (G1) or with low-F concentrations (G2 and G3) have shown a statistically significant difference between SMHi and SMHf values (H=66.00; p= 0.0000). Regarding %SMHC, it was observed a statistically high %SMHC in G1 (50.47). G2 (42.89) and G3 (28.94) followed in descending order by G4 (12.15); G5 (5.71) and G6 (4.81) which were not statistically different. SEM and 3-D images have shown smoother surfaces in high F toothpastes compared to F-free or with low-F.
Conclusions: It was concluded that, children's toothpastes with low-F concentrations (500 - 750 ppm) do not show the same anticaries effect as conventional toothpaste.