Stability of Optical and Mechanical Properties in Multi‐Shade, Group‐Shade, and Single‐Shade Resin Composites

<b>Objectives:</b> To investigate the effect of various immersion media on the optical, mechanical, and surface properties of multi-shade (MS), group-shade (GS), and single-shade (SS) dental resin composite (RC). <b>Materials and Methods:</b> Three different RCs (MS, GS, and SS) were involved in this study (<i>n</i> = 8/group). Rectangular specimens (10 mm × 10 mm × 2 mm) were fabricated and thermocycled in artificial saliva, black coffee, and red wine for 10,000 cycles. Color stability (∆E₀₀), relative translucency parameter (RTP), surface roughness (Sa), and Vickers hardness (VH) were measured. Data were statistically analyzed (SPSS v27) and surfaces analyzed under scanning electron microscopy. <b>Results:</b> All ∆E₀₀ values exceeded the acceptability and perceptibility threshold (PT). All RC exhibited statistically significant changes in RTP, Sa, and VH after 10,000 thermal cycling (<i>p</i> < 0.001). There are statistically significant changes of ∆E₀₀ and translucency for specimens immersed in red wine (<i>p</i> < 0.001). No immersion media exert statistically significant changes on Sa (<i>p</i> = 0.004) and hardness (<i>p</i> < 0.086). <b>Conclusions:</b> SS RC shows the best stability in both optical and mechanical properties, whereas GS RC exhibits variable performance with no trend requiring further investigations. The MS RC shows the least color and translucency stability but highest hardness throughout the experiment.