Dental Composites for Wide Color Matching

Dental fillings are selected according to the color of the patient's tooth. Therefore, the dentists have around a dozen colors for each product in stock. Still, after a certain period of time, the choice could become suboptimal as the hard tooth tissue alters, for example, owing to specific habits such as smoking. Nanotechnology-based composites can at least partially master this deficiency. Similar to a chameleon, a filling with such a composite can match the color of the surrounding enamel. In this study, we thoroughly investigated the nanostructure of one such composite and the related optical properties. The size of the spherical silica-zirconia fillers and their arrangement in micrometer-sized domains was examined using electron microscopy, synchrotron radiationbased nanotomography and small-angle X-ray scattering. The optical properties were derived from transmission measurements ranging from the ultraviolet to the infrared spectrum. Isotropic dielectric homogenization was used to model the optical properties based on the nanostructure. We could deduce the diameter of the spheres, which corresponds to 260 nm. The spheres show a narrow size distribution and form micrometer-sized domains with close-packed nanospheres along their borders. Homogenization was not sufficient to predict all features of the transmission spectrum. The gathered structural information is a basis to gain deeper understanding of the chameleon effect and the methodology can be applied to other single-shade dental composites.