Preparation and properties of nano-sized calcium fluoride for dental applications

Objectives The aim of the present study was to prepare nano-sized calcium fluoride (CaF2) that could be used as a labile F reservoir for more effective F regimens and as an agent for use in the reduction of dentin permeability. Methods Nano-sized CaF2 powders were prepared using a spray-drying system with a two-liquid nozzle. The properties of the nano-CaF2 were studied and the effectiveness of a fluoride (F) rinse with nano-CaF2 as the F source was evaluated. The thermodynamic solubility product of the nano-CaF2 solution was determined by equilibrating the nanosample in solutions presaturated with respect to macro-CaF2. Reactivity of the nano-CaF2 was assessed by its reaction with dicalcium phosphate dehydrate (DCPD). F deposition by 13.2 mmol/L F rinse with the nano-CaF2 as the F source was determined using a previously published in vitro model. Results X-ray diffraction (XRD) analysis showed pattern of low crystalline CaF2. BET measurements showed that the nano-CaF2 had a surface area of 46.3 m2/g, corresponding to a particle size of 41 nm. Transmission electron microscopy (TEM) examinations indicated that the nano-CaF2 contained clusters comprising particles of (10–15) nm in size. The nano-CaF2 displayed much higher solubility and reactivity than its macro-counterpart. The CaF2 ion activity product (IAP) of the solution in equilibrium with the nano-CaF2 was (1.52 ± 0.05) × 10−10, which was nearly four times greater than the Ksp (3.9 × 10−11) for CaF2. The reaction of DCPD with nano-CaF2 resulted in more F-containing apatitic materials compared to the reaction with macro-CaF2. The F deposition by the nano-CaF2 rinse was (2.2 ± 0.3) μg/cm2 (n = 5), which was significantly (p < 0.001) greater than that ((0.31 ± 0.06) μg/cm2) produced by the NaF solution. Significance The nano-CaF2 can be used as an effective anticaries agent in increasing the labile F concentration in oral fluid and thus enhance the tooth remineralization. It can also be very useful in the treatment for the reduction of dentin permeability.