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

The objective of this study is to develop novel CaF 2 /SiO 2 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. The CaF 2 /SiO 2 NCs were efficiently fabricated by assembling CaF 2 /SiO 2 nanoparticles (NPs) as building blocks with a spray-drying technology. CaF 2 /SiO 2 NCs with different SiO 2 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 CaF 2 /50SiO 2 NCs (50 represents 50 wt% SiO 2 coating amount) in the DRCs was investigated, while CaF 2 /50SiO 2 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. Spherical CaF 2 /50SiO 2 NCs with an average size of 2.4 µm were obtained at the feed rate of 7.4 mL/min and the CaF 2 /50SiO 2 NPs solid content of 2 wt% in the suspension. The optimum comprehensive performances of the DRCs can be achieved by filling 55 wt% CaF 2 /50SiO 2 NCs. Compared with CaF 2 /50SiO 2 NPs, the filling amount of CaF 2 /50SiO 2 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 CaF 2 /50SiO 2 NCs were improved by 9.8%, 17.7%, 7.5% and 69.8%, respectively. Furthermore, the DRCs filled with 50 wt% CaF 2 /50SiO 2 NCs exhibited more cumulative F-release by 126% and more stable F-release rate than the counterpart filled with 50 wt% CaF 2 /50SiO 2 NPs after immersed for 1800 h. And 55 wt% CaF 2 /50SiO 2 NCs filled DRCs could inhibit the growth of S. mutans, reaching an antibacterial ratio of 93%. The spray-dried CaF 2 /50SiO 2 NCs are promising fillers for the development of high-performance multifunctional DRCs. [ABSTRACT FROM AUTHOR]