(39a) Radiopaque flame-made Ta2O5/SiO2 nanoparticles with controlled refractive index and transparency | AIChE

(39a) Radiopaque flame-made Ta2O5/SiO2 nanoparticles with controlled refractive index and transparency


Schulz, H. - Presenter, ETH Zürich
Pratsinis, S. E. - Presenter, Swiss Federal Institute of Technology, Particle Technology Laboratory, ETH Zurich
Burtscher, P. - Presenter, Ivoclar Vivadent AG
Moszner, N. - Presenter, Ivoclar Vivadent AG

Dental fillings made of composite organic monomers and ceramic fillers (particles) are used for tooth shaded dental restoration of anterior lesions and small - medium sized defects in the posterior region. This is a result of the excellent esthetic properties of these fillings as well as health concerns with amalgam fillings regarding mercury release. Therefore, the relation of filler properties to composite characteristics such as radiopacity, tensile strength, hardness, shrinkage, wear and transparency have been intensively studied in the last few years. Mixed Ta2O5-containing SiO2 powders with high specific surface area, controlled refractive index, transparency and crystallinity were prepared by flame spray pyrolysis as fillers for dental composites. The production rate ranged from 6.7 ? 100 g/h in a lab scale reactor. The effect of the Ta-precursor, the solvent, the total metal concentration and the Ta-content were studied by nitrogen adsorption, x-ray diffraction, light microscopy, HRTEM, DIFTS analysis, as well as the composite transparency within a polymer matrix of dimethylacrylate for dental restoration applications. Filler properties such as transparency, crystallinity and Ta-dispersion in the SiO2 matrix altered the composite performance. Ta2O5 crystallites and a low Ta-dispersion within the SiO2 matrix decreased the filler and composite transparency. Powders with identical specific surface area, refractive index and Ta2O5-loading (24 wt%) showed a wide range of composite transparencies from 33 ? 78 % depending on filler properties. Fillers with an amorphous structure, a high Ta-dispersion and a matching refractive index with the polymer matrix showed the highest composite transparency of 86 % for a 16.5 wt% filler loading including 35 wt% Ta2O5 giving an optimal radiopacity.


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