Nano-tomography of dental composites with wide color matching

Dental restorations should match the color of the surrounding enamel. Carefully selecting the appropriate shade for the filling material is a challenge for dentists. Moreover, tooth color can change over time due to habits such as smoking or drinking coffee. In the last few years, single-shade dental composites have come to the market. They rely on a chameleon effect to provide acceptable to good color matching regardless of the tooth color. The chameleon effect refers to a dental filling's ability to guide light in such a way that its color blends in with that of the tooth. Structural color is a contributing factor to the chameleon effect and an active area of research where structures at the submicron scale play a critical role. We investigated the size, shape, and three-dimensional spatial arrangement of filler particles in single-shade dental resin composites. Cylindrical samples of dental composites were prepared and imaged with the transmission X-ray microscope at the ANATOMIX beamline, Synchrotron SOLEIL, France. The centers of the filler particles were determined from the tomography data. Combined with shape information from scanning electron microscopy, a Monte Carlo approach was used to model the transmittance for light at wavelengths from the visible to the ultraviolet. The results were compared to optical transmission measurements. The combination of nanotomography and simulation can thus help to understand the influence of the size and distribution of filler particles on the chameleon effect.