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

Abstract

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.