Effect of fluoride gels supplemented with nano-sized sodium trimetaphosphate on enamel remineralization in situ

OBJECTIVES: This study evaluated the effect of fluoride gels supplemented with nano-sized sodium trimetaphosphate (TMP) on remineralization of artificial caries lesions in situ. MATERIALS AND METHODS: Bovine enamel blocks (n = 160) with chemically-induced caries-like lesions were randomly distributed into four groups: Placebo (without F and TMP - negative control), 9000 µg F/g (9000F - positive control), 4500 µg F/g + 5 % micrometric TMP (4500F+5 % TMPmicro), and 4500 µg F/g + 5 % nano-sized TMP (4500F+5 %TMPnano). Ten volunteers used palatal devices containing 4 demineralized enamel blocks for 3 days, following a double-blind and crossover protocol. Two enamel blocks were removed immediately after gel application to determine calcium fluoride (CaF2) formed. After each phase, the samples were analyzed for the percentage of surface hardness recovery (%SHR), cross-sectional hardness (ΔKHN), and CaF2 retained on enamel. The data were submitted to one-way (%SHR and ΔKHN) or two-way (CaF2), repeated-measures ANOVA, followed by Student-Newman-Keuls test (p < 0.05). RESULTS: The highest %SHR was observed for 4500F+5 %TMPnano gel, followed by 4500F+5 %TPMmicro, 9000F, and Placebo, with significant differences among all groups. An inverse pattern was verified for ΔKHN, with the highest and lowest values achieved by the Placebo and 4500+5 %TMPnano groups, respectively. Regarding CaF2 formed, the highest concentration was observed in the 9000F group. For CaF2 retained, no significant differences were observed among all fluoride-containing gels. CONCLUSION: The low-fluoride gel containing TMP led to significantly higher remineralization rates than a conventional gel containing twice as much fluoride; nano-sized TMP resulted in enhanced remineralization compared with micrometric particles. CLINICAL SIGNIFICANCE: The experimental formulation significantly outperformed the conventional fluoride gel in promoting enamel remineralization. These findings suggest a promising and safer alternative to current topical fluoride therapies, with important implications for caries prevention, both for private practice and in public health programs.