Optimising Material Ratios for Full-Colour 3D-Printed Dental Restorations

Accurate colour reproduction remains a challenge in manufactured dental restorations because tooth appearance depends on wavelength-dependent absorption and scattering, geometry, illumination, and viewing conditions. We present a measurement- and simulation-based workflow for determining 3D-printable multi-material compositions. We demonstrate our workflow by reproducing the appearance of the 16 VITA classical A1–D4 shade guide colours with a set of six Stratasys Vero and VeroUltra photopolymers. Each reference tooth was recorded in a photobox using a camera with six narrow-band spectral filters spanning 450 nm to 700 nm. A physics-based, GPU-accelerated Monte Carlo light transport simulation was then used inversely to recover the six material concentrations that minimised the CIE ΔE2000 colour difference between the measured and simulated appearance considering all six wavelength bands. Additionally, we compared four colour optimisation strategies for determining material compositions. We further investigated metamerism in the colour optimisation by independently the illuminant and comparing a single- and double-light-source setup. These variations produced substantial changes in the resulting colour differences. With the given material set, the resulting mixtures reproduced all 16 teeth across the shade guide with a mean colour difference of CIE ΔE2000=2.76±0.88 over the evaluated tooth regions. Crucially, the printing materials require optical characterisation only once, after which new target teeth need only be spectrally measured to determine their printable compositions. More broadly, the framework provides a general route from spectral measurements to physically realisable multi-material reproductions, extending beyond dental applications.