Effects of coffee thermocycling on surface roughness, microhardness, and color stability of permanent crown materials

Abstract Permanent crown resins manufactured by additive technologies are increasingly used for definitive restorations, yet their resistance to combined thermal and chemical aging remains incompletely characterized. This in vitro study compared four 3D-printed permanent crown resins (VarseoSmile TriniQ, NextDent C&B MFH, CROWNTEC, and Permanent Crown Resin) with a milled composite-based CAD/CAM material (CeraSmart 270). Disk-shaped specimens ( n = 10/group) were evaluated for surface roughness, surface morphology, microhardness, and color before and after 10,000 coffee thermocycles between 5 °C and 55 °C. Surface roughness increased significantly in all materials. After aging, CeraSmart 270 showed the lowest Ra (0.159 ± 0.005 μm) and highest Vickers hardness (93.87 ± 4.80 HV), whereas Permanent Crown Resin showed the highest Ra (0.322 ± 0.014 μm), lowest hardness (20.22 ± 1.40 HV), and greatest color change (ΔE*ab = 4.19 ± 0.30). Permanent Crown Resin and NextDent C&B MFH exceeded the predefined ΔE*ab reference value of 3.3. Coffee thermocycling produced material-dependent effects, with CeraSmart 270 showing greater overall stability than the tested 3D-printed resins under the conditions of this study.