Color-gradient lithium disilicate restorations fabricated via vat photopolymerization based on computer-assisted...

To fabricate personalized color-gradient dental lithium disilicate (LD) glass-ceramics by integrating computer-assisted color matching (CCM) with vat photopolymerization (VP).

The particle size and elemental composition of zirconium silicate (ZrSiO₄)-based pigments were evaluated using laser diffraction and energy-dispersive X-ray spectroscopy analysis, respectively. 45 vol% resin-based slurries doped with Fe-Pr-V/ZrSiO₄ pigments were prepared. The rheological behavior and exposure parameters of monochromatic gradient-concentration slurries were analyzed using shear-rate sweep and working-curve methods. Diffuse-reflectance spectroscopy was used to establish a CCM database and evaluate the color-matching accuracy of LD based on the VITA 3D-Master shade guide. The sintering behavior of five LD ceramic shades (1M2-5M2) was evaluated using thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction, and their densities were determined using porosity analysis. The mechanical properties of the five classical shades of LD ceramics were evaluated via flexural strength testing, Weibull modulus analysis, fracture-toughness testing, Vickers indentation, and nanoindentation. A color-gradient maxillary central incisor crown was fabricated and its 3D accuracy was evaluated.

Pigment particle sizes ranged from 5.9 to 8.9 μm with no interfacial defects in the LD matrix. Slurry viscosities at 50 °C were 2.3-2.5 Pa·s, while the red slurry required the highest exposure energy (12.2-16.7 mJ/cm²). Among the 26 predicted shades, 24 showed ΔE*ab < 3.7. After sintering, the relative density of the LD exceeded 99.5%. The LD specimens exhibited flexural strength of 380-428 MPa, fracture toughness of 2.94-3.50 MPa m¹ ᐟ², Weibull modulus > 10, Vickers hardness of 630-660 HV, and elastic modulus of 104-107 GPa. The color-gradient crown showed a root mean square deviation of 86.2 ± 5.7 μm.

This study demonstrates the integration of CCM and VP to fabricate color-gradient LD restorations, providing a precise and personalized strategy for esthetic dental application.