This study evaluated the effects of thermocycling and staining on the optical behavior, chemical stability, and surface morphology of three commercial dental composites manufactured using different polymerization protocols: a light-cured composite (Omnichroma, OMNI) and two digital light-processed (DLP) 3D-printed composites intended for permanent (SprintRay CROWN, SPRINT) and temporary (GC Temp PRINT, TEMP) clinical applications. Disc-shaped specimens were subjected to thermocycling (0, 5000, 10,000, and 30,000 cycles) and immersion in coffee, Coca-Cola, or red wine for 1 and 7 days. Color change (ΔE₀₀) and translucency parameter (TP) were determined spectrophotometrically, while Fourier-transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) were employed to assess the polymerization efficiency (expressed as the relative conversion index) and surface morphology, respectively. Thermocycling induced material-dependent changes in color stability and translucency. After 30,000 cycles, ΔE₀₀ values reached 2.77 ± 0.89 for OMNI, 0.74 ± 0.34 for SPRINT, and 3.30 ± 0.89 for TEMP. SPRINT maintained the highest TP values throughout the aging protocol, ranging from 26.09 ± 0.33 to 23.81 ± 1.93, whereas OMNI and TEMP exhibited lower TP values. The most favorable optical performance and the highest resistance to beverage-induced coloration were detected for SPRINT, whereas TEMP showed the greatest susceptibility to aging- and staining-induced optical degradation. Red wine and coffee produced substantially greater color changes and reductions in translucency than Coca-Cola. AFM analysis demonstrated progressive surface degradation and increased roughness following prolonged thermocycling, highlighting the significant influence of material composition and manufacturing protocol on the long-term optical stability of the investigated dental composites.

Backround: The aim of this study was to evaluate the effects of probiotic yogurt containing Lactobacillus rhamnosus (LGG) on the microhardness and surface roughness of restorative dental materials commonly used in pediatric dentistry. Methods: Three materials were tested: conventional glass ionomer cement Fuji II, high-viscosity glass ionomer cement Fuji IX, and microhybrid composite resin Te Econom. The samples were prepared according to the manufacturers’ instructions, initially stored in distilled water, and subsequently immersed in probiotic yogurt. Microhardness was measured by the Vickers hardness test, and surface roughness was assessed by 3D profilometers. Results: Statistical analysis was performed using the Wilcoxon signed-rank test and the Kruskal–Wallis test. Exposure to probiotic yogurt resulted in increased microhardness for the resin-modified and high-viscosity glass ionomer cements, whereas the microhardness of the microhybrid composite resin decreased. The surface roughness increased for all the tested materials, with statistically significant differences observed in most groups (p < 0.05). Conclusions: These findings indicate that probiotic yogurt can alter the physical properties of restorative dental materials and highlight the importance of careful selection of preventive agents in pediatric dental practice. Further research is needed to clarify the long-term effects of probiotic preparations on dental restorations.