Effects of At-Home Bleaching on Color Stability and Surface Roughness of Single-Shade, ORMOCER-Based, and...

Background/Objectives: This study evaluated the effects of at-home bleaching on color stability (ΔE) and surface roughness (Ra) of a single-shade nanohybrid composite, an ORMOCER-based composite, and a conventional nanohybrid resin composite, acknowledging that bleaching represents only one of several clinical ageing challenges. Methods: One hundred and five extracted, non-carious human molars received standardized Class I restorations and were randomly allocated to five groups (n = 21): an ORMOCER-based composite (Admira Fusion), a single-shade composite (Omnichroma), Omnichroma bonded with an alternative universal adhesive, and two conventional nanohybrid composites (Filtek Supreme Ultra and Harmonize). Baseline and experimental color (CIELAB, ΔE) were measured with a spectrophotometer, and surface roughness (Ra) was measured using a 3D optical profilometer. Specimens underwent five bleaching cycles using 22% carbamide peroxide, with each cycle consisting of 8 h of bleaching followed by 16 h of storage in artificial saliva at 37 °C. Measurements were taken at baseline and after each cycle. The data were analyzed using a repeated-measures ANOVA, with bleaching cycle as the within-subject factor, the effect sizes reported as partial eta-squared (ηp²), and the statistical significance set at α = 0.05. Results: All restorative materials exhibited progressive color change with repeated bleaching, and ΔE values exceeded established clinical acceptability thresholds across materials. The extent of color change varied among materials. None of the evaluated materials maintained clinically acceptable color stability following repeated bleaching cycles. The single-shade composite (Omnichroma) demonstrated the greatest magnitude of color change, particularly when bonded with Scotchbond Universal Bond. Admira Fusion and Filtek Supreme Ultra had lower ΔE values but still exceeded acceptability thresholds. Surface roughness generally decreased following bleaching, with statistically significant reductions in Ra observed for multiple materials. Admira Fusion and Omnichroma bonded with Tokuyama Universal Bond showed minimal surface alteration. Conclusions: All restorative materials demonstrated clinically unacceptable color changes following bleaching, indicating limited esthetic stability under bleaching conditions. ORMOCER-based composites showed comparatively greater resistance to surface roughness alterations.