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 SiO2 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 CaF2/SiO2 core–shell nanoparticles (CaF2/SiO2 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.% CaF2/50%SiO2 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 CaF2 nanoparticles. In addition, the initial F-release rate of RCs containing 50 wt.% CaF2/50%SiO2 NPs was 2.5 ± 0.4 μg/(h cm2), while the sustained release rate and the F release ratio were 0.96 ± 0.15 μg/h·cm2 and 5.22‰ after 1632 h (68 days), respectively. It was much more stable and sustained compared with the counterpart filled with CaF2 NPs. Therefore, it could be envisioned that CaF2/SiO2 NPs have a great potential as inorganic fillers in dental RCs.