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


CONCLUSIONS
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.
Sun
Limin
L
American Dental Association Foundation Paffenbarger Research Center, Polymers Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899-8546, USA. limin.sun@nist.gov
Chow
Laurence C
LC
D001031:Apatites / Q000138:chemical synthesis; D002124:Calcium Fluoride / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D002130:Calcium Phosphates / Q000737:chemistry; D002327:Cariostatic Agents / Q000008:administration & dosage / Q000737:chemistry* / Q000494:pharmacology; D018360:Crystallography, X-Ray; D003806:Dentin Permeability / Q000187:drug effects; D005459:Fluorides / Q000008:administration & dosage / Q000494:pharmacology; D009067:Mouthwashes / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D014089:Tooth Remineralization / Q000379:methods
D001031:Apatites; D002130:Calcium Phosphates; D002327:Cariostatic Agents; D009067:Mouthwashes; C025105:fluorapatite; D002124:Calcium Fluoride; C494366:calcium phosphate, dibasic, dihydrate; D005459:Fluorides