Effect of color shade on the accuracy, surface hardness and degree of conversion of 3D-printed resin materials

The effect of resin shade on the manufacturing accuracy and mechanical properties of three-dimensional (3D)-printed provisional restorations remains unclear. The purpose of this in vitro study was to evaluate the effect of resin shade on manufacturing accuracy, surface hardness, and degree of conversion of provisional restorations produced using digital light processing (DLP) 3D printing systems. A photopolymer resin in four different shades (A2, A3, B1, and B2) was used to fabricate 96 specimens using a DLP 3D printer (Asiga Max 2, Asiga). In each shade group, eight specimens were produced as three-unit fixed dental prostheses to evaluate manufacturing accuracy. The remaining specimens were prepared as discs (10 mm diameter, 3 mm thickness) for surface hardness and degree of conversion analyses. Manufacturing accuracy was evaluated by comparing printed restorations with reference CAD data using 3D analysis software and calculating root mean square (RMS) deviations. Surface hardness was measured using a microhardness tester (HV0.05; 490.3 mN). The degree of conversion was determined using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Statistical analyses were performed using one-way analysis of variance (ANOVA) and Tukey tests (α = 0.05). Resin shade significantly affected external manufacturing accuracy and surface hardness ( p < .05). The A3 shade demonstrated the highest surface hardness and the most favorable external accuracy values. No statistically significant differences were observed in internal accuracy or degree of conversion ( p > .05). Resin shade may influence the external manufacturing accuracy and surface hardness of DLP-printed provisional restorations, although the differences observed remained within clinically acceptable limits. Shade selection should therefore be considered not only for esthetics but also for its potential effect on production accuracy and material performance.