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 (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.

Methods: 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 13.2 mmol/L F rinse with the nano-CaF(2) as the F source was determined using a previously published in vitro model.

Results: 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)x10(-10), which was nearly four times greater than the K(sp) (3.9 x 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)mug/cm(2) (n=5), which was significantly (p<0.001) greater than that ((0.31+/-0.06)mug/cm(2)) produced by the NaF solution.

Significance: 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.