Dental fillings (composites) made of 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 aesthetic properties of these fillings and there are no health concerns in contrast to 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.
High radiopacity, a property conventionally provided by the ceramic filler, is needed for x-ray detection of the filling. For nanocomposites of organic monomers including Ta2O5 or TiO2 particles, excellent radiopacity was observed. However, the tensile strength of composites containing Ta2O5 particles below 100 nm decreased at high filler content. Grafting the particle surface enhanced particle bonding with the polymer matrix and increased tensile strength and hardness.
The composite wear is significantly lower for nanometer- than for micrometer-size particles. High initial transparency of the dental filler is desired as the opacity of dental filling is adjusted to the patient’s tooth color by opaque additives. Excellent composite translucence was observed when matching the polymer and ceramic refractive indices (RI). The RI of mixed oxides can be controlled over the range of the RI of its components. In this regard Ta2O5/SiO2 gives a broad range of RI while the Ta presence provides the radiopacity. Mixed Ta2O5/SiO2 has no absorption band in the visible spectrum and can have a high transparency as desired in dental applications.
Recent, relevant references:
- H. Schulz, L. Mädler, S. E. Pratsinis, P. Burtscher, and N. Moszner, "Transparent Nanocomposites of Radiopaque, Flame-Made Ta2O5/SiO2 in an Acrylic Matrix", Adv. Funct. Mater., 15 (5), 830-837 (2005)
- L. Mädler, F. Krumeich, P. Burtscher, N. Moszner, „Transparent and radiopaque inorganic organic composites from flame-made mixed oxide fillers”, J. Nanopart. Res., 8, 323-333 (2006)
- H. Schulz, B. Schimmoeller, S. E. Pratsinis, U. Salz, T. Bock; "Radiopaque dental adhesives: Dispersion of flame-made Ta2O5/SiO2 nanoparticles in methacrylic matrices", Journal of Dentistry, 36 579-587 (2008)