Effects of Post-Curing Duration on Color Changes in 3D-Printed Fixed Polymeric Restorations of Varying Thicknesses

To evaluate color changes in 3D-printed acrylic restorations of varying thicknesses and exposed to different post-curing durations.

Three virtual full-contour maxillary central incisor crowns with different buccal thicknesses (1.0, 1.5, and 2.0 mm) were designed and manufactured using a 3D printer and a photopolymer (n = 9 per thickness group). The lightness, hue, and chroma of the restorations were measured at baseline (prior to post-curing) and again at 5-minute intervals up to 30 minutes during the post-curing process using a spectrophotometer. Color changes (ΔE) were calculated by comparing the CIE L*, a*, b* coordinates at different time points to the baseline values. Repeated-measures ANOVA and Tukey post-hoc tests were used for statistical analysis (α = .05).

The ΔE increased significantly within the first 5 minutes of post-curing and was more gradual thereafter in all thickness groups. The ΔE values were significantly higher in the 1.5- and 2.0-mm-thickness groups compared to the 1.0-mm-thickness group. The C* coordinate was seen to increase significantly within the first 5 minutes of post-curing and did not change significantly afterward.

During post-curing, the hue of 3D-printed polymeric restorations changed to yellowish and reddish shades, the brightness decreased, and the saturation increased. Most color changes occurred within the first 5 minutes of post-curing and were also more noticeable in thicker restorations.