Effect of Different Mouthwashes on the Hardness and Color Stability of CAD/CAM Materials: An In Vitro Study

Objective: To evaluate the effect of different mouthwashes on the microhardness and color stability of two CAD/CAM restorative materials. Methods: A total of 60 rectangular samples (2 mm × 7 mm × 12 mm) were prepared by sectioning two CAD/CAM materials (NICE and Lava Ultimate) and divided into six groups according to material type and immersion solution: distilled water (DW, control), hydrogen peroxide (HP), and povidone-iodine (PVP-I). Microhardness and color parameters (L*, a*, b*) were measured at baseline and after 30 days of immersion, and the ΔE00 color difference was calculated. Data were analyzed using t-tests, two-way and one-way ANOVA, and Tukey’s post hoc test. Results: After 30 days of immersion, both materials showed a significant decrease in microhardness following treatment with HP and PVP-I (NICE from ~823 to ~720 HV and ~709 HV; LAVA from ~197 to ~142 HV and ~113 HV, respectively). Regarding color, ΔE00 values exceeded the clinically acceptable threshold (ΔE00 > 1.8), with no significant differences between the two materials (p > 0.05). Within each material, ΔE00 was significantly higher in both mouthwash groups compared to the control (p < 0.001), but no significant difference was observed between the two antimicrobial solutions (p > 0.05). Conclusion: Within the limitations of this study, the microhardness and color stability of both CAD/CAM restorations may be susceptible to degradation after prolonged exposure to HP and PVP-I mouthwashes.