The Evaluation of Water Sorption Effects on Surface Characteristics and Color Changes in Direct and CAD/CAM Subtractively Processed Resin Composites

This study investigates the influence of water immersion on direct composite resins in comparison with subtractive processed composite resins. It evaluates changes in their optical characteristics, surface roughness, solubility, and water sorption. Four CAD/CAM materials (Vita Enamic, Brilliant, Cerasmart, and Tetric) and three direct composite resins (Gradia Direct Anterior A2, Tetric Evo Ceram A2, and Filtek Z550 A2) were examined. Direct composite samples were created using a 3D-printed mold, compressed, and photopolymerized, whereas CAD/CAM samples were sectioned and processed to the same dimensions. Seventy samples (n = 10) were prepared. After dehydration and initial weighing, samples were immersed in distilled water for 30 days, with mass changes recorded at multiple time points. Surface roughness and optical parameters were measured at three stages: post-dehydration, post-immersion, and post-reconditioning. ANOVA, unpaired and paired Student's <i>t</i>-tests, and Pearson correlation coefficient were used to evaluate the variables. The drawn conclusion was that there were significant differences both between stages and between the materials. The most stable material in terms of water sorption was Vita Enamic. Regarding the optical parameters, Brilliant, Vita, and Cerasmart displayed higher stability, while Tetric CAD, Tetric, Gradia, and Filtek showed increased sensitivity to water immersion and re-desiccation. Gradia exhibited the highest surface roughness, while the CAD-CAM materials demonstrated the greatest stability.