Spray-drying-assisted fabrication of CaF2/SiO2 nanoclusters for dental restorative composites

ObjectiveThe objective of this study is to develop novel CaF₂/SiO₂ nanoclusters (NCs) fillers, which can endow the dental resin composites (DRCs) with excellent mechanical properties, stable and sustained fluoride ion release, and good antibacterial activity.MethodsThe CaF₂/SiO₂ NCs were efficiently fabricated by assembling CaF₂/SiO₂ nanoparticles (NPs) as building blocks with a spray-drying technology. CaF₂/SiO₂ NCs with different SiO₂ coating amounts (20 wt%, 50 wt% and 80 wt%) were incorporated into the DRCs at the filler content of 55 wt% for the measurement of mechanical properties including flexural strength, flexural modulus, compressive strength, and hardness. The effect of the filling amount of CaF₂/50SiO₂ NCs (50 represents 50 wt% SiO₂ coating amount) in the DRCs was investigated, while CaF₂/50SiO₂ NPs were adopted as comparison group. The fluoride ion release and antibacterial activity of the DRCs with the optimal mechanical performances were evaluated. Furthermore, the statistical analyses were performed for mechanical properties.ResultsSpherical CaF₂/50SiO₂ NCs with an average size of 2.4 µm were obtained at the feed rate of 7.4 mL/min and the CaF₂/50SiO₂ NPs solid content of 2 wt% in the suspension. The optimum comprehensive performances of the DRCs can be achieved by filling 55 wt% CaF₂/50SiO₂ NCs. Compared with CaF₂/50SiO₂ NPs, the filling amount of CaF₂/50SiO₂ NCs was increased by 5 wt% (50–55 wt%), and under the same filling amount of 50 wt%, the flexural strength, flexural modulus, compressive strength, and hardness of the DRCs containing CaF₂/50SiO₂ NCs were improved by 9.8%, 17.7%, 7.5% and 69.8%, respectively. Furthermore, the DRCs filled with 50 wt% CaF₂/50SiO₂ NCs exhibited more cumulative F-release by 126% and more stable F-release rate than the counterpart filled with 50 wt% CaF₂/50SiO₂ NPs after immersed for 1800 h. And 55 wt% CaF₂/50SiO₂ NCs filled DRCs could inhibit the growth of S. mutans, reaching an antibacterial ratio of 93%.SignificanceThe spray-dried CaF₂/50SiO₂ NCs are promising fillers for the development of high-performance multifunctional DRCs.