In Vitro Comparison of Gingival Epithesis Materials: Color Stability, Surface Properties, and Microbial Adhesion After Staining

Background: This in vitro study compared color stability, surface properties, and microbial adhesion of four gingival epithesis materials (silicone: Gingivamoll®; nylon: Valplast®; PETG-based high-performance polymer: Eldy Plus®; PMMA: Palapress®) after staining. Methods: Standardized specimens (10 × 10 × 2 mm; n = 18/material) underwent 15 or 30 staining cycles (sequential immersion in coffee, curry, tea, and 40% alcohol). Color (CIELAB) and color difference (ΔE00), gloss (G), and surface roughness (Ra) were measured at baseline and after 15 and 30 cycles; surface morphology was assessed by SEM. Microbial adhesion was assessed using a six-species biofilm model and quantified as log CFU at baseline and after 15 and 30 cycles. Results: All materials showed clinically relevant discoloration (ΔE00 > 2). Valplast® exhibited the greatest color change (p < 0.05), while color change in other materials remained lower. Gingivamoll® showed the lowest gloss and highest roughness, whereas other materials remained smoother; roughness increased significantly over time (p < 0.05). SEM revealed a coating on the hard materials and nodular agglomerates on silicone. Biofilm CFU did not differ over time or between materials (all p > 0.05). Conclusions: Staining induced material-dependent changes in color and surface properties, with Valplast® most prone to discoloration and silicone showing high roughness and nodular surface changes, contrasting with coatings on hard materials. Microbial adhesion analysis yielded pilot-level results, intended to inform the design of future investigations.