Color Stainability of Graphene-Reinforced PMMA Compared to CAD/CAM PMMA in Different pH Media

Statement of problem: CAD/CAM PMMA needs to improve its color stability as used for long-term provisional restoration.Purpose: To evaluate the nanographene-reinforced PMMA surface roughness after thermocycling and color stainability after immersion in coffee and ginger (two different pH media) to frequently used pre-polymerized PMMA. Methods: Sixty CAD/CAM interim materials discs were divided into two groups (n=30): PMMA (P) and graphene-reinforced PMMA (G). All specimens were polished according to the manufacturer's instructions, followed by artificial accelerated aging. Surface roughness (Ra) was analyzed using a non-contact profilometer. Then, both tested groups were immersed in 3 different pH media (coffee, ginger, and distilled water) (n=10) for 3 and 7 days. The color difference (ΔE) was assessed. All data were statistically analyzed.Results: Thermocycling did not significantly change mean Ra (P-value=0.172, Effect size=0.150) between tested materials. After 3 days of coffee or ginger immersion, group (P) showed a significant decrease in mean ΔE compared to group (G). The two materials were not statistically different after distilled water immersion. After 7 days of coffee immersion, group (P) showed a significant rise in mean ΔE compared to group (G). After ginger immersion, the two materials did not differ significantly. After distilled water immersion, group (P) showed a significant reduction in mean ΔE compared to group (G). However, both materials showed unacceptable color change clinically (ΔE3.3). Conclusion: Nanographene-reinforced PMMA had no significant improvement regarding surface roughness after thermocycling and color stainability after immersion in different pH media compared with frequently used CAD/CAM PMMA.