The aim of the present study was to prepare nano-sized calcium fluoride (CaF 2 ) 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.Nano-sized CaF 2 powders were prepared using a spray-drying system with a two-liquid nozzle. The properties of the nano-CaF 2 were studied and the effectiveness of a fluoride (F) rinse with nano-CaF 2 as the F source was evaluated. The thermodynamic solubility product of the nano-CaF 2 solution was determined by equilibrating the nanosample in solutions presaturated with respect to macro-CaF 2 . Reactivity of the nano-CaF 2 was assessed by its reaction with dicalcium phosphate dehydrate (DCPD). F deposition by 13.2mmol/L F rinse with the nano-CaF 2 as the F source was determined using a previously published in vitro model.X-ray diffraction (XRD) analysis showed pattern of low crystalline CaF 2 . BET measurements showed that the nano-CaF 2 had a surface area of 46.3m 2 /g, corresponding to a particle size of 41nm. Transmission electron microscopy (TEM) examinations indicated that the nano-CaF 2 contained clusters comprising particles of (10–15) nm in size. The nano-CaF 2 displayed much higher solubility and reactivity than its macro-counterpart. The CaF 2 ion activity product (IAP) of the solution in equilibrium with the nano-CaF 2 was (1.52±0.05)×10 −10 , which was nearly four times greater than the K sp (3.9×10 −11 ) for CaF 2 . The reaction of DCPD with nano-CaF 2 resulted in more F-containing apatitic materials compared to the reaction with macro-CaF 2 . The F deposition by the nano-CaF 2 rinse was (2.2±0.3)μg/cm 2 (n=5), which was significantly (p<0.001) greater than that ((0.31±0.06)μg/cm 2 ) produced by the NaF solution.The nano-CaF 2 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.