Influence of printing orientation and post-curing on optical and surface properties of definitive three-dimensional-printed dental resin with inorganic fillers

This study evaluated the influence of printing orientation and post-curing on the color stability, gloss retention, and surface microhardness of a definitive three-dimensional (3D)-printed dental resin, a high-strength photopolymer with inorganic fillers designed for permanent restorations, after immersion in a staining solution. Circular specimens (6 mm diameter and 1.5 mm thickness) were printed at 0°, 45°, and 90° orientations and divided into two groups: control (n = 10), post-cured according to the manufacturer's protocol, and negative control (n = 10), without post-curing. Baseline color (L^*, a^*, b^*), gloss, and Knoop microhardness were measured, followed by reassessment after 21 days of immersion in a staining solution. Data were analyzed using two-way and repeated-measures analysis of variance (α = 0.05). Non-post-cured specimens showed perceptible but clinically acceptable color changes. Microhardness decreased after staining in all groups, regardless of curing. Gloss significantly diminished post-staining, with the control group printed at 45° showing superior retention. Printing orientation influenced color stability, with the 0° orientation showing the highest stability. Post-curing enhanced color stability and gloss retention in definitive 3D-printed resins. Printing orientation affected optical outcomes, emphasizing the importance of optimizing both parameters for long-term esthetic and mechanical reliability.