Mechanical performance and color stability of 3D-printed ceramic-filled resin following various bleaching regimens: an in vitro study.

BACKGROUND: Recent material science advancements enabled a 3D-printable ceramic-filled resin for restorations. Additive manufacturing produces crowns, veneers, and mock-ups. Office and home bleaching agents contact teeth and restoration surfaces during application, potentially altering material properties. OBJECTIVES: The aim of the study is to assess the compressive strength, flexural strength, surface microhardness, surface roughness, and color changes of the additive 3D-printed ceramic-filled resin before and after exposure to home and in-office tooth bleaching. METHODS: A total of 150 specimens were equally distributed into control (non-bleaching), home-bleaching (16% carbamide peroxide), and in-office bleaching (40% hydrogen peroxide) groups (n = 50/group). Compressive strength was evaluated using a universal testing machine, flexural strength by a four-point bending test, surface microhardness using a Vickers hardness tester, surface roughness using a 3D optical profilometer, and color changes using a spectrophotometer based on the CIEDE2000 (ΔE00) system. Statistical analysis was performed using one-way ANOVA, Tukey post-hoc tests, and independent t-tests (α = 0.05). RESULTS: Both home bleaching (16% carbamide peroxide) and in-office bleaching (40% hydrogen peroxide) significantly reduced the compressive strength, flexural strength, and surface microhardness of the 3D-printed ceramic-filled resin while significantly increasing surface roughness (P ≤ 0.05). The in-office bleaching group exhibited significantly greater reductions in mechanical properties and higher surface roughness values than the home-bleaching group. Although bleaching produced statistically significant color changes, all ΔE00 values remained below the clinically acceptable threshold. CONCLUSIONS: Home bleaching (16% carbamide peroxide) and in-office bleaching (40% hydrogen peroxide) reduced compressive and flexural strength, microhardness, and increased roughness of 3D-printed crowns. In-office bleaching showed greater effects, while color changes remained clinically acceptable.