Color stability of heat-polymerized and autopolymerized soft denture liners

Statement of problem. The physical and mechanical properties of soft dentur e liners are influenced by a number of factors. Aging is one factor that ha s an effect on the characteristics of polymers. The resistance of denture l iners to aging can potentially influence the color stability of these liner s. Purpose. This study attempted to determine the color stability of soft line rs by subjecting them to an in vitro accelerated aging test. Material and methods. Two autopolymerizing and 3 heat polymerizing commerci ally available soft denture lining materials were tested. Seven sample disk s were made of each material according to manufacturers' instructions. Colo r measurements were recorded before and after the accelerated aging process . Color changes (Delta E) were calculated by measuring tristimulus values a t several wavelengths in the visual spectrum with the use of Commission Int ernational 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 valu es. Ufigel P and Simpa liner materials showed significantly greater color c hanges than the other tested materials. There were no significant differenc es in color change among Ufigel L-Molloplast B, Ufigel L-Flexor, and Mollop last B-Flexor liner materials. However, a significant difference in color c hange was found between Ufigel P and Simpa liners. Conclusion. Heat-polymerized soft liners were more color stable than autopo lymerized soft liners. No significant differences were found among heat pol ymerized materials; however, significant differences in color change were f ound between the 2 autopolymerized liners.