CaF2/SiO2 core–shell nanoparticles as novel fillers with reinforced mechanical properties and sustained fluoride ion release for dental resin composites

The good mechanical performances and caries inhibition of resin composites (RCs) are of great importance in dental restoration. Generally, the addition of SiO 2 can improve the mechanical properties of RCs, while the introduction of fluoride (F) ions is capable of preventing caries. In this work, we first report the use of CaF 2 /SiO 2 core–shell nanoparticles (CaF 2 /SiO 2 NPs) as novel fillers for developing RCs with excellent mechanical properties and sustained F release. The results show that the superior performances of RCs can be obtained by filling 50 wt.% CaF 2 /50%SiO 2 NPs, where the flexural strength, flexural modulus, compressive strength, and hardness were, respectively, increased by 111.5%, 41.4%, 61.7% and 66.8%, compared with the RCs filled with CaF 2 nanoparticles. In addition, the initial F-release rate of RCs containing 50 wt.% CaF 2 /50%SiO 2 NPs was 2.5 ± 0.4 μg/(h cm 2 ), while the sustained release rate and the F release ratio were 0.96 ± 0.15 μg/h·cm 2 and 5.22‰ after 1632 h (68 days), respectively. It was much more stable and sustained compared with the counterpart filled with CaF 2 NPs. Therefore, it could be envisioned that CaF 2 /SiO 2 NPs have a great potential as inorganic fillers in dental RCs. Graphical abstract