Optical properties, surface roughness, and bacterial adhesion of feldspathic CAD/CAM ceramic material after immersion in staining media with different pH

This study aimed to evaluate the effects of acidic and alkaline staining solutions on the optical-mechanical properties of feldspathic (Vitablocs Mark II) Computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic materials after 4 weeks of immersion in media. Specifically, this investigation focused on assessing mean colour change (ΔE*), the translucency parameter (TP00), the opalescence parameter (OPBW), surface roughness, and bacterial adhesion by colony-forming unit (CFU) count. A total of 96 Vitablocs Mark II CAD/CAM ceramic specimens were prepared and assigned to eight groups (A–H) according to the type of immersion solution: smokeless snuff, Black Shammah, Yerba mate, Saudi Coffee, MIRINDA Citrus, CodeRed, Nescafe, and normal saline (control group). The specimens were immersed for 4 weeks at 37 °C, with solutions replaced according to manufacturer instructions. Optical parameters, including ΔE*, TP00, and OPBW, were measured using a spectrophotometer (VITA Easyshade V). Surface roughness was analysed through white light interferometric microscopy, and the bacterial adhesion of Streptococcus mutans was quantified by calculating colony-forming units (CFUs) per square millimetre. Statistical analysis included Shapiro–Wilk tests for normality, one-way ANOVA, Tukey HSD post-hoc comparisons, and paired t-tests, with significance set at p < 0.05. The recorded pH values of the staining solutions ranged from acidic (MIRINDA Citrus: 3.25) to alkaline (Black Shammah: 9.45). Black Shammah exhibited the highest ΔE* value (6.75 ± 5.21), followed by smokeless snuff (6.53 ± 3.59). The lowest value (2.41 ± 1.04) was observed for Yerba mate, and significant differences were observed across staining solutions (p < 0.001). TP00 significantly decreased post-immersion, and the highest mean reduction was observed in CodeRed (5.87 ± 0.92; p < 0.001). By contrast, OPBW increased significantly, with the most significant mean increase observed in Black Shammah (6.93 ± 5.38; p = 0.001) and the smallest in Saudi coffee (1.19 ± 1.77; p = 0.040). Surface roughness varied among groups, ranging from 0.458 ± 0.04 (CodeRed) to 0.739 ± 0.03 µm (smokeless snuff). Bacterial adhesion was the highest in CodeRed (480.08 ± 40.77 CFUs) and lowest in normal saline (273.00 ± 42.29 CFUs; ANOVA, p < 0.001). Exposure to staining media significantly decreased translucency and increased opalescence, surface roughness, and bacterial adhesion in feldspathic CAD/CAM ceramic. Acidic solutions promoted greater Streptococcus mutans adhesion, while alkaline tobacco products caused the highest color change.