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 m(2)/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) x 10(-10), which was nearly four times greater than the Ksp (3.9 x 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) mu g/cm(2) (n = 5), which was significantly (p < 0.001) greater than that ((0.31 +/- 0.06) mu g/cm(2)) 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 (c) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.