Surface Roughness of Direct, 3D-Printed and CAD/CAM Restorative Materials Following Different Bleaching Protocols

This in vitro study compared the effects of in-office and at-home bleaching on the surface roughness of restorative materials produced by direct, subtractive, and additive manufacturing. Ninety-nine specimens were fabricated from Neo Spectra ST (NS), Cerasmart 270 (CS), and Saremco print Crowntec (CT). The specimens were assigned to in-office bleaching with 40% hydrogen peroxide (3 × 20 min) or at-home bleaching with 16% carbamide peroxide applied for 6 h/day over 14 days. Ra and Rz were recorded before and after bleaching by contact profilometry, and individual changes (ΔRa, ΔRz) were calculated. SEM provided qualitative assessment of surface morphology. Statistical analyses were performed at a significance level of α = 0.05. Both bleaching systems resulted in a significant increase in mean Ra and Rz values compared with baseline for all materials (p < 0.05). In-office bleaching resulted in higher Ra for CT (p = 0.019) and higher Rz for NS (p = 0.032) than at-home bleaching. ΔRa and ΔRz were comparable among materials (p > 0.05). SEM demonstrated qualitative surface alterations after bleaching. Nevertheless, all post-bleaching Ra values remained below 0.2 μm, indicating that the observed changes remained within a commonly cited clinically acceptable range under the conditions of this study.