Comparative Analysis of the Effects of Acidic and Alkaline Beverages on the Optical Properties, Surface Topography, and Bacterial Activity of Zirconia Materials.

This study aimed to evaluate how acidic and alkaline staining solutions affect the optical properties (mean color change, ΔE*), geometric characteristics (surface roughness, Ra), and bacterial adhesion of zirconia Ceramill Zolid PS computer-aided design/computer-aided manufacture (CAD/CAM) material after 21 days of immersion. Ninety-six zirconia CAD/CAM Ceramill Zolid multilayer PS specimens were prepared and allocated to eight groups based on the pH values of the immersion solutions; the acidic solutions included Mirinda Citrus, CodeRed, yerba mate tea, Saudi coffee, and Nescafe (A-E), and the alkaline solutions included artificial saliva, DZRT (tobacco-free nicotine pouches), and smokeless tobacco (F-H). The specimens were immersed for 21 days at 37 °C, with the solutions replaced every 12 h to ensure consistency. Color changes were measured using a VITA Easyshade V spectrophotometer, and Ra was evaluated via white-light interferometric microscopy. The bacterial adhesion of Streptococcus mutans was quantified by counting colony-forming units (CFUs, CFU/mm²). Statistical analyses included the Shapiro-Wilk test for normality, one-way ANOVA with Tukey's HSD post hoc test for group comparisons, and paired t-tests, with significance set at <0.05. The recorded pH values of the staining materials ranged from acidic (Mirinda Citrus: 3.23) to alkaline (smokeless tobacco: 8.54). Smokeless tobacco caused the most unacceptable mean color change (ΔE* = 6.84), followed by DZRT (ΔE* = 6.46), whereas artificial saliva produced the least discoloration (ΔE* = 2.15), with statistically significant differences among the solutions (p < 0.001). The Ra measurements varied significantly (p < 0.001), with Nescafe demonstrating the lowest value (0.486 µm) and DZRT the highest (0.748 µm). S. mutans adhesion was the highest for CodeRed (546.75 CFU) and the lowest for smokeless tobacco (283.92 CFU), demonstrating significant variation across groups (ANOVA, p < 0.001). The acidic and alkaline solutions significantly altered the optical properties, Ra, and bacterial adhesion of zirconia Ceramill Zolid PS CAD/CAM, with acidic solutions leading to higher bacterial adhesion.