In vitro color stability, stain resistance, and water sorption of four removable gingival flange materials

Statement of problem. Evaluation of the color stability of materials used for removable gingival flange prostheses may provide information on their serviceability. Purpose. This in vitro study compared the color stability, Stain resistance, and water sorption of 4 materials commonly used for gingival flange prostheses. Material and methods. Forty-five cylindrical disks (15 rum in diameter and 10 mm thick) were fabricated out of 1 silicone (Gingivamoll), I copolyamidc (Flexite Supreme), and 2 heat-polymerized acrylic resins (QC-20 and Vertex). Ten specimens of each material were evaluated by a spectrophotometer after 7, 14, 30, 60, 120, and 180 days of immersion in staining solutions of coffee and real whereas specimens placed in water and exposed to air, served as controls. Color differences before staining and after storage periods were assessed. Another 5 specimens of each material were tested for water sorption after 56 days. Data for color change (DeltaE) and weight difference (DeltaW) were analyzed by use of a repeated measures analysis of variance and Scheffe's multiple comparisons (alpha=.05). Results. The coffee solution produced the highest discoloration value in the silicone material (DeltaE=7.31 +/-0.57, P<.001), followed by the copolyamide (DeltaE=4.22 +/- 0.40, P<.001), and 2 acrylic resins. In the tea solution, the copolyamide had the greatest staining (DeltaE=2.74 +/- 0.56), whereas the other materials had smaller color changes (P<.001). All investigated materials were relatively color stable (DeltaE < 2) when stored in air and water for 6 months. The copolyamide material showed the greatest water uptake, whereas silicone adsorbed the least water (P<.001). Conclusions. All flange materials tested demonstrated color stability in air and water. However, the color changes of silicone and copolyamide materials stored in coffee solution for 180 days were greater than 3 NBS (National Bureau of Standards) units, which would be characterized as appreciable and considered clinically unacceptable.