Color stability of heat-polymerized and autopolymerized soft denture liners

Statement of problem. The physical and mechanical properties of soft denture liners are influenced by a number of factors. Aging is one factor that has an effect on the characteristics of polymers. The resistance of denture liners to aging can potentially influence the color stability of these liners. Purpose. This study attempted to determine the color stability of soft liners by subjecting them to an in vitro accelerated aging test. Material and methods. Two autopolymerizing and 3 heat polymerizing commercially available soft denture lining materials were tested. Seven sample disks were made of each material according to manufacturers' instructions. Color measurements were recorded before and after the accelerated aging process. Color changes (Delta E) were calculated by measuring tristimulus values at several wavelengths in the visual spectrum with the use of Commission International de 1'Eclairge Lab (CIE-LAB) uniform color scale. Results. Kruskall-Wallis variance analysis and Mann-Whitney U-Wilcoxon rank sum W tests were per formed for statistical comparison of the Delta E values. Ufigel P and Simpa liner materials showed significantly greater color changes than the other tested materials. There were no significant differences in color change among Ufigel L-Molloplast B, Ufigel L-Flexor, and Molloplast B-Flexor liner materials. However, a significant difference in color change was found between Ufigel P and Simpa liners. Conclusion. Heat-polymerized soft liners were more color stable than autopolymerized soft liners. No significant differences were found among heat polymerized materials; however, significant differences in color change were found between the 2 autopolymerized liners.