Anticaries effects of the experimental solutions containing niobium pentafluoride.

Objective: To develop, characterize and assess the in vitro effects of experimental niobium pentafluoride (NbF₅) solutions on preventing dental caries.

Materials and methods: NbF₅ solutions were developed and evaluated for fluoride concentration (after 1 and 6 months of preparation) and cytotoxicity (MTT for fibroblasts and preodontoblastic cells). Bovine enamel blocks (n = 176) were randomly assigned into groups of treatment: NbF₅ (0.25%, 0.5%, and 1% corresponding to 1,263.75; 2,527.5; and 5,055 ppm F⁻), NaF (0.29%, 0.57%, and 1.13% with fluoride levels matched to NbF₅), and controls (growth and sterility). The enamel blocks were partially covered and exposed to artificial saliva (1 h) before they were subjected to cariogenic challenge with a multispecies biofilm (37 °C; 24 h and 48 h) in culture medium enriched with 2% sucrose. The pH and total soluble fluoride (TSF) content of the medium were evaluated, and the enamel surface microhardness loss (%SML), volumetric roughness (Sa), tooth structure loss (TSL), and scanning electron microscopy (SEM) results were also evaluated. The data were analyzed by the Kruskal‒Wallis, Mann‒Whitney and Wilcoxon tests (p < 0.05).

Results: The fluoride concentrations remained stable across all storage periods with no significant variation, and similar stabilities were observed for both the NbF₅ and NaF solutions. The viability of MTT fibroblasts ranged from 94% ± 3.2% for 0.25% NbF₅ to 76% ± 2.9% for 1.0% NbF₅, whereas for MTT preodontoblastic cells, it ranged from 89% ± 3.8-70% ± 4.1% for the same concentrations. In contrast, NaF maintained 100% viability for both cell types, indicating lower cytotoxicity than NbF₅. The 1% NbF₅ and 1.13% NaF solutions presented the highest pH values, with no significant difference between them (p > 0.05). Both compounds also resulted in comparable TSF release patterns, with higher concentrations resulting in lower TSF levels, suggesting greater fluoride uptake into the enamel. The 1% NbF₅ (21.15 ± 10.12 and 37.31 ± 10.15) and 1.13% NaF solutions (22.12 ± 11.11 and 39.09 ± 13.24) presented the lowest %SMLs at 24 h and 48 h, respectively, with no significant difference between them (p > 0.05). Compared with those of the lower concentration groups, the Sa and TSL of the 1% NbF₅ and 1.13% NaF groups also exhibited equivalent and superior preventive effects (p < 0.05). SEM and profilometry analysis confirmed similar enamel surface preservation in both the 1% NbF₅ and the 1.13% NaF groups, with less porosity and mineral loss than in the other groups.

Conclusion: The in vitro results of the 1% NbF₅ solution revealed the potential of niobium pentafluoride to prevent dental caries, demonstrating equivalent effectiveness to NaF in maintaining enamel integrity, pH stability, and fluoride uptake, although with slightly greater cytotoxicity at the cellular level.

Clinical relevance:  The 1% NbF₅ solution had anticaries effects comparable to those of NaF, with stable fluoride release and acceptable biocompatibility, indicating its potential as an alternative compound for professional caries prevention.